// vim: ts=4 sw=4 expandtab ft=c

// Copyright (C) 1998-2008,2010,2012 The University of Melbourne.
// Copyright (C) 2017-2018, 2020 The Mercury team.
// This file is distributed under the terms specified in COPYING.LIB.

// This module implements the mdb commands in the "browsing" category.
//
// The structure of these files is:
//
// - all the #includes
// - local macros and declarations of local static functions
// - one function for each command in the category
// - any auxiliary functions
// - any command argument strings
// - option processing functions.

#include "mercury_std.h"
#include "mercury_getopt.h"
#include "mercury_string.h"

#include "mercury_trace_internal.h"
#include "mercury_trace_cmds.h"
#include "mercury_trace_cmd_browsing.h"
#include "mercury_trace_cmd_parameter.h"
#include "mercury_trace_vars.h"
#include "mercury_trace_hold_vars.h"
#include "mercury_trace_browse.h"
#include "mercury_trace_util.h"

#include "mdb.listing.mh"
#include "mdb.diff.mh"
#include "mdb.declarative_execution.mh"
#include "mdbcomp.program_representation.mh"

////////////////////////////////////////////////////////////////////////////

static  void        MR_trace_set_level_and_report(int ancestor_level,
                        MR_bool detailed, MR_bool print_optionals);
static  const char  *MR_trace_browse_exception(MR_EventInfo *event_info,
                        MR_Browser browser, MR_BrowseCallerType caller,
                        MR_BrowseFormat format);
static  const char  *MR_trace_browse_proc_body(MR_EventInfo *event_info,
                        MR_Browser browser, MR_BrowseCallerType caller,
                        MR_BrowseFormat format);

// Functions to invoke the user's web browser on terms or goals.
static  void        MR_trace_browse_web(MR_Word type_info, MR_Word value,
                        MR_BrowseCallerType caller, MR_BrowseFormat format);
static  void        MR_trace_browse_goal_web(MR_ConstString name,
                        MR_Word arg_list, MR_Word is_func,
                        MR_BrowseCallerType caller, MR_BrowseFormat format);

static  void        MR_trace_cmd_stack_2(MR_EventInfo *event_info,
                        MR_bool detailed, MR_FrameLimit frame_limit,
                        int line_limit);

static  const char  *MR_trace_new_source_window(const char *window_cmd,
                        const char *server_cmd, const char *server_name,
                        int timeout, MR_bool force, MR_bool verbose,
                        MR_bool split);

static  MR_bool     MR_trace_options_detailed(MR_bool *detailed,
                        char ***words, int *word_count);
static  MR_bool     MR_trace_options_stack_trace(MR_bool *print_all,
                        MR_bool *detailed, MR_SpecLineLimit *line_limit,
                        MR_SpecLineLimit *clique_line_limit,
                        MR_FrameLimit *frame_limit,
                        char ***words, int *word_count);
static  MR_bool     MR_trace_options_print(MR_BrowseFormat *format,
                        MR_Unsigned *max_printed_actions,
                        MR_bool *set_max_printed_actions,
                        char ***words, int *word_count);
static  MR_bool     MR_trace_options_browse(MR_BrowseFormat *format,
                        MR_bool *web,
                        char ***words, int *word_count);
static  MR_bool     MR_trace_options_view(const char **window_cmd,
                        const char **server_cmd, const char **server_name,
                        MR_Unsigned *timeout, MR_bool *force, MR_bool *verbose,
                        MR_bool *split, MR_bool *close_window,
                        char ***words, int *word_count);
static  MR_bool     MR_trace_options_diff(MR_Unsigned *start,
                        MR_Unsigned *max, char ***words, int *word_count);
static  MR_bool     MR_trace_options_dump(MR_bool *quiet, MR_bool *xml,
                        MR_bool *prettyprint, char ***words, int *word_count);

////////////////////////////////////////////////////////////////////////////

MR_Next
MR_trace_cmd_level(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_Unsigned n;
    MR_bool     detailed;
    MR_Level    selected_level;

    detailed = MR_FALSE;
    if (! MR_trace_options_detailed(&detailed, &words, &word_count)) {
        // The usage message has already been printed.
        ;
    } else if (word_count == 2 &&
        ( MR_streq(words[1], "clique") || MR_streq(words[1], "clentry") ))
    {
        if (MR_find_clique_entry_mdb(event_info, MR_CLIQUE_ENTRY_FRAME,
            &selected_level))
        {
            // The error message has already been printed.
            return KEEP_INTERACTING;
        }
    } else if (word_count == 2 && MR_streq(words[1], "clparent")) {
        if (MR_find_clique_entry_mdb(event_info, MR_CLIQUE_ENTRY_PARENT_FRAME,
            &selected_level))
        {
            // The error message has already been printed.
            return KEEP_INTERACTING;
        }
    } else if (word_count == 2 && MR_trace_is_natural_number(words[1], &n)) {
        selected_level = n;
    } else if (word_count == 1) {
        selected_level = 0;
    } else {
        MR_trace_usage_cur_cmd();
        return KEEP_INTERACTING;
    }

    MR_trace_set_level_and_report(selected_level, detailed,
        MR_print_optionals);
    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_up(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_Unsigned n;
    MR_bool     detailed;

    detailed = MR_FALSE;
    if (! MR_trace_options_detailed(&detailed, &words, &word_count)) {
        // The usage message has already been printed.
        ;
    } else if (word_count == 2 && MR_trace_is_natural_number(words[1], &n)) {
        MR_trace_set_level_and_report(MR_trace_current_level() + n, detailed,
            MR_print_optionals);
    } else if (word_count == 1) {
        MR_trace_set_level_and_report(MR_trace_current_level() + 1, detailed,
            MR_print_optionals);
    } else {
        MR_trace_usage_cur_cmd();
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_down(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_Unsigned n;
    MR_bool     detailed;

    detailed = MR_FALSE;
    if (! MR_trace_options_detailed(&detailed, &words, &word_count)) {
        // The usage message has already been printed.
        ;
    } else if (word_count == 2 && MR_trace_is_natural_number(words[1], &n)) {
        MR_trace_set_level_and_report(MR_trace_current_level() - n, detailed,
            MR_print_optionals);
    } else if (word_count == 1) {
        MR_trace_set_level_and_report(MR_trace_current_level() - 1, detailed,
            MR_print_optionals);
    } else {
        MR_trace_usage_cur_cmd();
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_vars(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    if (word_count == 1) {
        const char  *problem;

        problem = MR_trace_list_vars(MR_mdb_out);
        if (problem != NULL) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err, "mdb: %s.\n", problem);
        }
    } else {
        MR_trace_usage_cur_cmd();
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_held_vars(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    if (word_count == 1) {
        MR_trace_list_held_vars(MR_mdb_out);
    } else {
        MR_trace_usage_cur_cmd();
    }

    return KEEP_INTERACTING;
}

#define MR_NEXT_NUM_IO_ACTIONS_TO_PRINT     20
#define MR_ALL_NUM_IO_ACTIONS_TO_PRINT      500

MR_Next
MR_trace_cmd_print(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_BrowseFormat     format;
    MR_Unsigned         max_printed_actions;
    MR_bool             set_max_printed_actions;
    const char          *problem;
    MR_Unsigned         action;
    MR_Unsigned         lo_action;
    MR_Unsigned         hi_action;
    static MR_bool      have_next_io_action = MR_FALSE;
    static MR_Unsigned  next_io_action = 0;

    if (! MR_trace_options_print(&format,
        &max_printed_actions, &set_max_printed_actions, &words, &word_count))
    {
        // The usage message has already been printed.
        ;
    } else if (word_count == 1) {
        problem = MR_trace_browse_one_goal(MR_mdb_out,
            MR_trace_browse_goal_internal, MR_BROWSE_CALLER_PRINT, format);

        if (problem != NULL) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err, "mdb: %s.\n", problem);
        }
    } else if (word_count == 2) {
        if (MR_streq(words[1], "*")) {
            problem = MR_trace_browse_all(MR_mdb_out,
                MR_trace_browse_internal, format);
        } else if (MR_streq(words[1], "goal")) {
            problem = MR_trace_browse_one_goal(MR_mdb_out,
                MR_trace_browse_goal_internal, MR_BROWSE_CALLER_PRINT, format);
        } else if (MR_streq(words[1], "exception")) {
            problem = MR_trace_browse_exception(event_info,
                MR_trace_browse_internal, MR_BROWSE_CALLER_PRINT, format);
        } else if (MR_streq(words[1], "proc_body")) {
            problem = MR_trace_browse_proc_body(event_info,
                MR_trace_browse_internal, MR_BROWSE_CALLER_PRINT, format);
        } else if ((MR_streq(words[1], "io") || MR_streq(words[1], "action")))
        {
            MR_Unsigned num_printed_actions;

            if (!set_max_printed_actions) {
                max_printed_actions = MR_NEXT_NUM_IO_ACTIONS_TO_PRINT;
            }

            if (MR_io_tabling_phase == MR_IO_TABLING_BEFORE) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err,
                    "mdb: I/O tabling has not yet started.\n");
                return KEEP_INTERACTING;
            }

            if (MR_io_tabling_counter_hwm == 0) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err,
                    "mdb: There are no tabled I/O actions yet.\n");
                return KEEP_INTERACTING;
            }

            if (have_next_io_action && (!
                (MR_io_tabling_start <= next_io_action
                && next_io_action < MR_io_tabling_counter_hwm)))
            {
                have_next_io_action = MR_FALSE;
            }

            if (have_next_io_action) {
                lo_action = next_io_action;
            } else {
                lo_action = MR_io_tabling_start;
            }

            hi_action = lo_action + max_printed_actions;
            if (hi_action >= MR_io_tabling_counter_hwm) {
                hi_action = MR_io_tabling_counter_hwm - 1;
            }

            num_printed_actions = hi_action - lo_action + 1;
            if (num_printed_actions <= 0) {
                fprintf(MR_mdb_out, "There are no I/O actions to print\n");
                have_next_io_action = MR_FALSE;
            } else {
                for (action = lo_action; action <= hi_action; action++) {
                    fprintf(MR_mdb_out,
                        "action %" MR_INTEGER_LENGTH_MODIFIER "u: ", action);
                    problem = MR_trace_browse_action(MR_mdb_out, action,
                        MR_trace_browse_goal_internal,
                        MR_BROWSE_CALLER_PRINT, format);

                    if (problem != NULL) {
                        fflush(MR_mdb_out);
                        fprintf(MR_mdb_err, "mdb: %s.\n", problem);
                        return KEEP_INTERACTING;
                    }
                }

                if (hi_action == MR_io_tabling_counter_hwm - 1) {
                    fprintf(MR_mdb_out,
                        "there are no more actions (yet)\n");
                } else {
                    fprintf(MR_mdb_out,
                        "there are more actions, up to action "
                        "%" MR_INTEGER_LENGTH_MODIFIER "u\n",
                        MR_io_tabling_counter_hwm - 1);
                }

                next_io_action = hi_action + 1;
                have_next_io_action = MR_TRUE;
            }
        } else {
            problem = MR_trace_parse_browse_one(MR_mdb_out, MR_TRUE, words[1],
                MR_trace_browse_internal, MR_BROWSE_CALLER_PRINT, format,
                MR_FALSE);
        }

        if (problem != NULL) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err, "mdb: %s.\n", problem);
        }
    } else if (word_count == 3 &&
        (MR_streq(words[1], "io") || MR_streq(words[1], "action")))
    {
        if (MR_io_tabling_phase == MR_IO_TABLING_BEFORE) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err,
                "mdb: I/O tabling has not yet started.\n");
            return KEEP_INTERACTING;
        }

        if (MR_io_tabling_counter_hwm == 0) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err,
                "mdb: There are no tabled I/O actions yet.\n");
            return KEEP_INTERACTING;
        }

        if (MR_streq(words[2], "limits")) {
            fprintf(MR_mdb_out,
                "I/O tabling has recorded actions "
                "%" MR_INTEGER_LENGTH_MODIFIER "u to "
                "%" MR_INTEGER_LENGTH_MODIFIER "u.\n",
                MR_io_tabling_start, MR_io_tabling_counter_hwm - 1);
            fflush(MR_mdb_out);
        } else if (MR_trace_is_natural_number(words[2], &action)) {
            if (! (MR_io_tabling_start <= action
                && action < MR_io_tabling_counter_hwm))
            {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err,
                    "I/O tabling has only recorded actions "
                    "%" MR_INTEGER_LENGTH_MODIFIER "u to "
                    "%" MR_INTEGER_LENGTH_MODIFIER "u.\n",
                    MR_io_tabling_start, MR_io_tabling_counter_hwm - 1);
                have_next_io_action = MR_FALSE;
                return KEEP_INTERACTING;
            }

            problem = MR_trace_browse_action(MR_mdb_out, action,
                MR_trace_browse_goal_internal,
                MR_BROWSE_CALLER_PRINT, format);

            if (problem != NULL) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err, "mdb: %s.\n", problem);
                have_next_io_action = MR_FALSE;
            }

            next_io_action = action + 1;
            have_next_io_action = MR_TRUE;
        } else if (MR_trace_is_natural_number_pair(words[2],
            &lo_action, &hi_action))
        {
            if (lo_action >= hi_action) {
                // Swap lo_action and hi_action.
                MR_Unsigned tmp;

                tmp = lo_action;
                lo_action = hi_action;
                hi_action = tmp;
            }

            if (! (MR_io_tabling_start <= lo_action
                && hi_action < MR_io_tabling_counter_hwm))
            {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err,
                    "I/O tabling has only recorded actions "
                    "%" MR_INTEGER_LENGTH_MODIFIER "u to "
                    "%" MR_INTEGER_LENGTH_MODIFIER "u.\n",
                    MR_io_tabling_start, MR_io_tabling_counter_hwm - 1);
                have_next_io_action = MR_FALSE;
                return KEEP_INTERACTING;
            }

            for (action = lo_action; action <= hi_action; action++) {
                fprintf(MR_mdb_out,
                    "action %" MR_INTEGER_LENGTH_MODIFIER "u: ", action);
                problem = MR_trace_browse_action(MR_mdb_out, action,
                    MR_trace_browse_goal_internal,
                    MR_BROWSE_CALLER_PRINT, format);

                if (problem != NULL) {
                    fflush(MR_mdb_out);
                    fprintf(MR_mdb_err, "mdb: %s.\n", problem);
                    return KEEP_INTERACTING;
                }
            }

            next_io_action = hi_action + 1;
            have_next_io_action = MR_TRUE;
        } else if (MR_streq(words[2], "*")) {
            if (!set_max_printed_actions) {
                max_printed_actions = MR_ALL_NUM_IO_ACTIONS_TO_PRINT;
            }

            lo_action = MR_io_tabling_start;
            hi_action = MR_io_tabling_counter_hwm - 1;

            if (lo_action + max_printed_actions < hi_action) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err,
                    "I/O tabling has recorded "
                    "%" MR_INTEGER_LENGTH_MODIFIER "d actions, "
                    "numbered %" MR_INTEGER_LENGTH_MODIFIER "u to "
                    "%" MR_INTEGER_LENGTH_MODIFIER "u.\n",
                    MR_io_tabling_counter_hwm + MR_io_tabling_start - 1,
                    MR_io_tabling_start, MR_io_tabling_counter_hwm - 1);
                if (set_max_printed_actions) {
                    fprintf(MR_mdb_err,
                        "Following your request via the -m option, "
                        "only the first %" MR_INTEGER_LENGTH_MODIFIER "u "
                        "actions will be printed.\n",
                        max_printed_actions);
                } else {
                    fprintf(MR_mdb_err,
                        "Without your explicit request via the -m option, "
                        "only the default maximum "
                        "of %" MR_INTEGER_LENGTH_MODIFIER "u "
                        "actions will be printed.\n",
                        max_printed_actions);
                }

                hi_action = lo_action + max_printed_actions - 1;
            }

            for (action = lo_action; action <= hi_action; action++) {
                fprintf(MR_mdb_out,
                    "action %" MR_INTEGER_LENGTH_MODIFIER "u: ", action);
                problem = MR_trace_browse_action(MR_mdb_out, action,
                    MR_trace_browse_goal_internal,
                    MR_BROWSE_CALLER_PRINT, format);

                if (problem != NULL) {
                    fflush(MR_mdb_out);
                    fprintf(MR_mdb_err, "mdb: %s.\n", problem);
                    return KEEP_INTERACTING;
                }
            }

            next_io_action = hi_action + 1;
            have_next_io_action = MR_TRUE;
        } else {
            MR_trace_usage_cur_cmd();
        }
    } else {
        MR_trace_usage_cur_cmd();
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_browse(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_BrowseFormat     format;
    MR_bool             web;
    MR_IoActionNum      action;
    MR_GoalBrowser      goal_browser;
    MR_Browser          browser;
    const char          *problem;

    if (! MR_trace_options_browse(&format, &web, &words, &word_count)) {
        // The usage message has already been printed.
        ;
    } else {
        if (web) {
            goal_browser = MR_trace_browse_goal_web;
            browser = MR_trace_browse_web;
        } else {
            goal_browser = MR_trace_browse_goal_internal;
            browser = MR_trace_browse_internal;
        }

        if (word_count == 1) {
            problem = MR_trace_browse_one_goal(MR_mdb_out, goal_browser,
                MR_BROWSE_CALLER_BROWSE, format);

            if (problem != NULL) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err, "mdb: %s.\n", problem);
            }
        } else if (word_count == 2) {
            if (MR_streq(words[1], "goal")) {
                problem = MR_trace_browse_one_goal(MR_mdb_out, goal_browser,
                    MR_BROWSE_CALLER_BROWSE, format);
            } else if (MR_streq(words[1], "exception")) {
                problem = MR_trace_browse_exception(event_info, browser,
                    MR_BROWSE_CALLER_BROWSE, format);
            } else if (MR_streq(words[1], "proc_body")) {
                problem = MR_trace_browse_proc_body(event_info, browser,
                    MR_BROWSE_CALLER_BROWSE, format);
            } else {
                problem = MR_trace_parse_browse_one(MR_mdb_out, MR_FALSE,
                    words[1], browser, MR_BROWSE_CALLER_BROWSE, format,
                    MR_TRUE);
            }

            if (problem != NULL) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err, "mdb: %s.\n", problem);
            }
        } else if (word_count == 3 &&
            (MR_streq(words[1], "io") || MR_streq(words[1], "action"))
            && MR_trace_is_natural_number(words[2], &action))
        {
            problem = MR_trace_browse_action(MR_mdb_out, action, goal_browser,
                MR_BROWSE_CALLER_BROWSE, format);

            if (problem != NULL) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err, "mdb: %s.\n", problem);
            }
        } else {
            MR_trace_usage_cur_cmd();
        }
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_stack(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_bool                 print_all;
    MR_bool                 detailed;
    MR_FrameLimit           frame_limit;
    MR_SpecLineLimit        clique_line_limit;
    MR_SpecLineLimit        line_limit;
    MR_SpecLineLimit        spec_line_limit;
    const MR_LabelLayout    *layout;
    MR_Word                 *saved_regs;
    const char              *msg;

    detailed = MR_FALSE;
    print_all = MR_FALSE;
    frame_limit = 0;
    clique_line_limit = 10;
    line_limit = 100;
    if (! MR_trace_options_stack_trace(&print_all, &detailed,
        &line_limit, &clique_line_limit, &frame_limit, &words, &word_count))
    {
        // The usage message has already been printed.
        return KEEP_INTERACTING;
    } else if (word_count == 1) {
        line_limit = MR_stack_default_line_limit;
    } else if (word_count == 2 &&
        MR_trace_is_natural_number(words[1], &spec_line_limit))
    {
        line_limit = spec_line_limit;
    } else {
        MR_trace_usage_cur_cmd();
        return KEEP_INTERACTING;
    }

    layout = event_info->MR_event_sll;
    saved_regs = event_info->MR_saved_regs;

#ifdef  MR_DEBUG_STACK_DUMP_CLIQUE
    MR_trace_init_modules();
    fprintf(MR_mdb_out, "OLD STACK DUMP:\n");
    msg = MR_dump_stack_from_layout(MR_mdb_out, layout,
        MR_saved_sp(saved_regs), MR_saved_curfr(saved_regs),
        detailed, MR_context_position != MR_CONTEXT_NOWHERE,
        frame_limit, line_limit,
        &MR_dump_stack_record_print);

    if (msg != NULL) {
        fflush(MR_mdb_out);
        fprintf(MR_mdb_err, "%s.\n", msg);
    }

    fprintf(MR_mdb_out, "\nNEW STACK DUMP:\n");
#endif
    msg = MR_dump_stack_from_layout_clique(MR_mdb_out, layout,
        MR_saved_sp(saved_regs), MR_saved_curfr(saved_regs),
        detailed, MR_context_position != MR_CONTEXT_NOWHERE,
        !print_all, clique_line_limit, frame_limit, line_limit,
        &MR_dump_stack_record_print);

    if (msg != NULL) {
        fflush(MR_mdb_out);
        fprintf(MR_mdb_err, "%s.\n", msg);
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_current(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    if (word_count == 1) {
        MR_trace_event_print_internal_report(event_info);
    } else {
        MR_trace_usage_cur_cmd();
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_view(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    const char      *window_cmd = NULL;
    const char      *server_cmd = NULL;
    const char      *server_name = NULL;
    MR_Unsigned     timeout = 8;    // In seconds.
    MR_bool         force = MR_FALSE;
    MR_bool         verbose = MR_FALSE;
    MR_bool         split = MR_FALSE;
    MR_bool         close_window = MR_FALSE;
    const char      *msg;

    if (! MR_trace_options_view(&window_cmd, &server_cmd, &server_name,
        &timeout, &force, &verbose, &split, &close_window,
        &words, &word_count))
    {
        // The usage message has already been printed.
        ;
    } else if (word_count != 1) {
        MR_trace_usage_cur_cmd();
    } else if (close_window) {
        MR_trace_maybe_close_source_window(verbose);
    } else {
        msg = MR_trace_new_source_window(window_cmd, server_cmd, server_name,
            timeout, force, verbose, split);
        if (msg != NULL) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err, "mdb: %s.\n", msg);
        }

        MR_trace_maybe_sync_source_window(event_info, verbose);
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_hold(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    char        *event_var_name;
    char        *held_var_name;
    MR_TypeInfo type_info;
    MR_Word     value;
    const char  *problem;
    MR_bool     bad_subterm;

    if (word_count == 2) {
        event_var_name = words[1];
        held_var_name = words[1];
    } else if (word_count == 3) {
        event_var_name = words[1];
        held_var_name = words[2];
    } else {
        MR_trace_usage_cur_cmd();
        return KEEP_INTERACTING;
    }

    if (strpbrk(held_var_name, "^/") != NULL) {
        // Don't allow path separators in variable names.
        MR_trace_usage_cur_cmd();
        return KEEP_INTERACTING;
    }

    if (held_var_name[0] == '$') {
        // Ignore any unneeded initial $ signs.
        held_var_name = &held_var_name[1];
    }

    problem = MR_trace_parse_lookup_var_path(event_var_name, &type_info,
        &value, &bad_subterm);
    if (problem != NULL) {
        fflush(MR_mdb_out);
        fprintf(MR_mdb_err, "mdb: %s%s.\n",
            (bad_subterm? "there is no path " : ""), problem);
        return KEEP_INTERACTING;
    }

    if (! MR_add_hold_var(held_var_name, type_info, value)) {
        fflush(MR_mdb_out);
        fprintf(MR_mdb_err, "mdb: there is already a held variable $%s\n",
            held_var_name);
    }

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_diff(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_Unsigned start;
    MR_Unsigned max;
    char        *name1;
    char        *name2;
    MR_TypeInfo type_info1;
    MR_TypeInfo type_info2;
    MR_Word     value1;
    MR_Word     value2;
    MR_Word     univ1;
    MR_Word     univ2;
    const char  *problem1;
    const char  *problem2;
    MR_bool     bad_subterm1;
    MR_bool     bad_subterm2;
    MercuryFile mdb_out;

    start = 0;
    max = 20;
    if (! MR_trace_options_diff(&start, &max, &words, &word_count)) {
        // The usage message has already been printed.
        return KEEP_INTERACTING;
    } else if (word_count != 3) {
        MR_trace_usage_cur_cmd();
        return KEEP_INTERACTING;
    }

    name1 = words[1];
    name2 = words[2];
    problem1 = MR_trace_parse_lookup_var_path(name1, &type_info1, &value1,
        &bad_subterm1);
    problem2 = MR_trace_parse_lookup_var_path(name2, &type_info2, &value2,
        &bad_subterm2);
    if (problem1 != NULL) {
        fflush(MR_mdb_out);
        fprintf(MR_mdb_err, "mdb: %s%s.\n",
            (bad_subterm1? "arg1: there is no path " : ""), problem1);
        return KEEP_INTERACTING;
    }
    if (problem2 != NULL) {
        fflush(MR_mdb_out);
        fprintf(MR_mdb_err, "mdb: %s%s.\n",
            (bad_subterm2? "arg2: there is no path " : ""), problem2);
        return KEEP_INTERACTING;
    }

    MR_c_file_to_mercury_file(MR_mdb_out, &mdb_out);
    MR_TRACE_CALL_MERCURY(
        MR_new_univ_on_hp(univ1, type_info1, value1);
        MR_new_univ_on_hp(univ2, type_info2, value2);
        ML_report_diffs(MR_wrap_output_stream(&mdb_out), start, max,
            univ1, univ2);
    );

    return KEEP_INTERACTING;
}

MR_Next
MR_trace_cmd_dump(char **words, int word_count, MR_TraceCmdInfo *cmd,
    MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    MR_Word         browser_term;
    const char      *value_problem = NULL;
    MR_bool         quiet = MR_FALSE;
    MR_bool         xml = MR_FALSE;
    MR_bool         prettyprint = MR_FALSE;

    // Set this to NULL to avoid uninitialization warnings.

    browser_term = (MR_Word) NULL;

    if (! MR_trace_options_dump(&quiet, &xml, &prettyprint,
        &words, &word_count))
    {
        // The usage message has already been printed.
        ;
    } else if (word_count != 3) {
        MR_trace_usage_cur_cmd();
    } else {
        if (MR_streq(words[1], "goal")) {
            const char  *name;
            MR_Word     arg_list;
            MR_bool     is_func;

            MR_convert_goal_to_synthetic_term(&name, &arg_list, &is_func);
            browser_term = MR_synthetic_to_browser_term(name, arg_list,
                is_func);
        } else if (MR_streq(words[1], "exception")) {
            MR_Word exception;

            exception = MR_trace_get_exception_value();
            if (exception == (MR_Word) NULL) {
                value_problem = "missing exception value";
            } else {
                browser_term = MR_univ_to_browser_term(exception);
            }
        } else if (MR_streq(words[1], "proc_body")) {
            const MR_ProcLayout     *entry;
            MR_Word                 rep;

            entry = event_info->MR_event_sll->MR_sll_entry;

            if (entry->MR_sle_body_bytes == NULL) {
                value_problem = "current procedure has no body bytecodes";
            } else {
                MR_TRACE_CALL_MERCURY(
                    MR_MDBCOMP_trace_read_proc_defn_rep(
                        entry->MR_sle_body_bytes,
                        event_info->MR_event_sll, &rep);
                );

                browser_term = MR_type_value_to_browser_term(
                    (MR_TypeInfo) ML_proc_defn_rep_type(), rep);
            }
        } else {
            MR_VarSpec  var_spec;
            MR_TypeInfo type_info;
            MR_Word     value;
            const char  *name;

            MR_convert_arg_to_var_spec(words[1], &var_spec);
            value_problem = MR_lookup_unambiguous_var_spec(var_spec,
                &type_info, &value, &name);
            if (value_problem == NULL) {
                browser_term = MR_type_value_to_browser_term(type_info, value);
            }
        }

        if (value_problem != NULL) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err, "mdb: %s.\n", value_problem);
        } else {
            if (xml && prettyprint) {
                fflush(MR_mdb_out);
                fprintf(MR_mdb_err,
                    "mdb: the -p and -x options of the \"dump\" command "
                    "are mutually exclusive; ignoring -p.\n");
            }

            if (xml) {
                MR_trace_save_term_xml(words[2], browser_term);
            } else if (prettyprint) {
                MR_trace_save_term_doc(words[2], browser_term);
            } else {
                MR_trace_save_term(words[2], browser_term);
            }

            if (!quiet) {
                fprintf(MR_mdb_out, "Dumped %s to %s\n", words[1], words[2]);
            }
        }
    }

    return KEEP_INTERACTING;
}

// list [num]
//
// List num lines of context around the line number of the context of the
// current point (i.e. level in the call stack). If num is not given,
// the number of context lines defaults to the value of the context_lines
// setting.
//
// TODO: add the following (use MR_parse_source_locn()):
// list filename:num[-num]
//
// List a range of lines from a given file. If only one number is given,
// the default number of lines of context is used.

MR_Next
MR_trace_cmd_list(char **words, int word_count,
    MR_TraceCmdInfo *cmd, MR_EventInfo *event_info, MR_Code **jumpaddr)
{
    const MR_ProcLayout     *entry_ptr;
    const char              *filename;
    int                     lineno;
    int                     first_lineno;
    int                     last_lineno;
    MR_Word                 *base_sp_ptr;
    MR_Word                 *base_curfr_ptr;
    MR_Unsigned             num = MR_num_context_lines;
    MR_String               aligned_filename;

    if (word_count > 2) {
        MR_trace_usage_cur_cmd();
        return KEEP_INTERACTING;
    }

    if (word_count == 2 && !MR_trace_is_natural_number(words[1], &num)) {
        MR_trace_usage_cur_cmd();
        return KEEP_INTERACTING;
    }

    MR_trace_current_level_details(&entry_ptr, &filename, &lineno,
        &base_sp_ptr, &base_curfr_ptr);

    MR_TRACE_USE_HP(
        MR_make_aligned_string(aligned_filename, (MR_String) filename);
    );

    first_lineno = lineno - num;
    last_lineno = lineno + num;
    if (first_lineno < 1) {
        first_lineno = 1;
    }

    if (MR_listing_cmd != NULL && strlen(MR_listing_cmd) > 0) {
        MR_TRACE_CALL_MERCURY(
            ML_LISTING_list_file_with_command(MR_mdb_out, MR_mdb_err,
                MR_listing_cmd, (char *) aligned_filename,
                first_lineno, last_lineno, lineno, MR_listing_path);
        );
    } else {
        MR_TRACE_CALL_MERCURY(
            ML_LISTING_list_file(MR_mdb_out, MR_mdb_err,
                (char *) aligned_filename,
                first_lineno, last_lineno, lineno, MR_listing_path);
        );
    }

    return KEEP_INTERACTING;
}

////////////////////////////////////////////////////////////////////////////

static void
MR_trace_set_level_and_report(int ancestor_level, MR_bool detailed,
    MR_bool print_optionals)
{
    const char              *problem;
    const MR_ProcLayout     *entry;
    MR_Word                 *base_sp;
    MR_Word                 *base_curfr;
    const char              *filename;
    int                     lineno;
    int                     indent;

    problem = MR_trace_set_level(ancestor_level, print_optionals);
    if (problem == NULL) {
        fprintf(MR_mdb_out, "Ancestor level set to %d:\n",
            ancestor_level);
        MR_trace_current_level_details(&entry, &filename, &lineno,
            &base_sp, &base_curfr);
        fprintf(MR_mdb_out, "%4d ", ancestor_level);
        if (detailed) {
            // We want to print the trace info first regardless
            // of the value of MR_context_position.

            MR_print_call_trace_info(MR_mdb_out, entry, base_sp, base_curfr);
            indent = 26;
        } else {
            indent = 5;
        }

        MR_print_proc_id_trace_and_context(MR_mdb_out, MR_FALSE,
            MR_context_position, MR_user_event_context, entry, MR_FALSE,
            base_sp, base_curfr, "", filename, lineno, MR_FALSE,
            "", 0, indent);
    } else {
        fflush(MR_mdb_out);
        fprintf(MR_mdb_err, "%s.\n", problem);
    }
}

void
MR_trace_browse_internal(MR_Word type_info, MR_Word value,
    MR_BrowseCallerType caller, MR_BrowseFormat format)
{
    switch (caller) {

        case MR_BROWSE_CALLER_BROWSE:
            MR_trace_browse(type_info, value, format);
            break;

        case MR_BROWSE_CALLER_PRINT:
        case MR_BROWSE_CALLER_PRINT_ALL:
            fprintf(MR_mdb_out, "\t");
            fflush(MR_mdb_out);
            MR_trace_print(type_info, value, caller, format);
            break;

        default:
            MR_fatal_error("MR_trace_browse_internal: unknown caller type");
    }
}

void
MR_trace_browse_goal_internal(MR_ConstString name, MR_Word arg_list,
    MR_Word is_func, MR_BrowseCallerType caller, MR_BrowseFormat format)
{
    switch (caller) {

        case MR_BROWSE_CALLER_BROWSE:
            MR_trace_browse_goal(name, arg_list, is_func, format);
            break;

        case MR_BROWSE_CALLER_PRINT:
            MR_trace_print_goal(name, arg_list, is_func, caller, format);
            break;

        case MR_BROWSE_CALLER_PRINT_ALL:
            MR_fatal_error("MR_trace_browse_goal_internal: bad caller type");

        default:
            MR_fatal_error("MR_trace_browse_goal_internal:"
                " unknown caller type");
    }
}

static const char *
MR_trace_browse_exception(MR_EventInfo *event_info, MR_Browser browser,
    MR_BrowseCallerType caller, MR_BrowseFormat format)
{
    MR_TypeInfo type_info;
    MR_Word     value;
    MR_Word     exception;

    if (event_info->MR_trace_port != MR_PORT_EXCEPTION) {
        return "command only available from EXCP ports";
    }

    exception = MR_trace_get_exception_value();
    if (exception == (MR_Word) NULL) {
        return "missing exception value";
    }

    MR_unravel_univ(exception, type_info, value);

    (*browser)((MR_Word) type_info, value, caller, format);

    return (const char *) NULL;
}

static const char *
MR_trace_browse_proc_body(MR_EventInfo *event_info, MR_Browser browser,
    MR_BrowseCallerType caller, MR_BrowseFormat format)
{
    const MR_ProcLayout     *entry;
    MR_Word                 rep;

    entry = event_info->MR_event_sll->MR_sll_entry;

    if (entry->MR_sle_body_bytes == NULL) {
        return "current procedure has no body info";
    }

    MR_TRACE_CALL_MERCURY(
        MR_MDBCOMP_trace_read_proc_defn_rep(entry->MR_sle_body_bytes,
            event_info->MR_event_sll, &rep);
    );

    (*browser)(ML_proc_defn_rep_type(), rep, caller, format);
    return (const char *) NULL;
}

static void
MR_trace_browse_web(MR_Word type_info, MR_Word value,
    MR_BrowseCallerType caller, MR_BrowseFormat format)
{
    MR_Word     browser_term;

    browser_term = MR_type_value_to_browser_term((MR_TypeInfo) type_info,
        value);

    MR_trace_save_and_invoke_web_browser(browser_term);
}

static void
MR_trace_browse_goal_web(MR_ConstString name, MR_Word arg_list,
    MR_Word is_func, MR_BrowseCallerType caller, MR_BrowseFormat format)
{
    MR_Word     browser_term;

    browser_term = MR_synthetic_to_browser_term(name, arg_list, is_func);
    MR_trace_save_and_invoke_web_browser(browser_term);
}

// Implement the `view' command. First, check if there is a server attached.
// If so, either stop it or abort the command, depending on whether '-f'
// was given. Then, if a server name was not supplied, start a new server
// with a unique name (which has been MR_malloc'd), otherwise attach to the
// server with the supplied name (and make a MR_malloc'd copy of the name).

static const char *
MR_trace_new_source_window(const char *window_cmd, const char *server_cmd,
    const char *server_name, int timeout, MR_bool force,
    MR_bool verbose, MR_bool split)
{
    const char  *msg;

    if (MR_trace_source_server.server_name != NULL) {
        // We are already attached to a server.

        if (force) {
            MR_trace_maybe_close_source_window(verbose);
        } else {
            return "error: server already open (use '-f' to force)";
        }
    }

    MR_trace_source_server.split = split;
    if (server_cmd != NULL) {
        MR_trace_source_server.server_cmd = MR_copy_string(server_cmd);
    } else {
        MR_trace_source_server.server_cmd = NULL;
    }

    if (server_name == NULL) {
        msg = MR_trace_source_open_server(&MR_trace_source_server,
                window_cmd, timeout, verbose);
    } else {
        MR_trace_source_server.server_name = MR_copy_string(server_name);
        msg = MR_trace_source_attach(&MR_trace_source_server, timeout,
            verbose);
        if (msg != NULL) {
            // Something went wrong, so we should free the
            // strings we allocated just above.

            MR_free(MR_trace_source_server.server_name);
            MR_trace_source_server.server_name = NULL;
            MR_free(MR_trace_source_server.server_cmd);
            MR_trace_source_server.server_cmd = NULL;
        }
    }

    return msg;
}

void
MR_trace_maybe_sync_source_window(MR_EventInfo *event_info, MR_bool verbose)
{
    const MR_LabelLayout    *parent;
    const char              *filename;
    int                     lineno;
    const char              *parent_filename;
    int                     parent_lineno;
    const char              *problem; // Not used.
    MR_Word                 *base_sp;
    MR_Word                 *base_curfr;
    const char              *msg;
    MR_Level                actual_level;

    if (MR_trace_source_server.server_name != NULL) {
        lineno = 0;
        filename = "";
        parent_lineno = 0;
        parent_filename = "";

        if (filename[0] == '\0') {
            (void) MR_find_context(event_info->MR_event_sll,
                &filename, &lineno);
        }

        // At interface ports we send both the parent context and the
        // current context. Otherwise, we just send the current context.

        if (MR_port_is_interface(event_info->MR_trace_port)) {
            base_sp = MR_saved_sp(event_info->MR_saved_regs);
            base_curfr = MR_saved_curfr(event_info->MR_saved_regs);
            parent = MR_find_nth_ancestor(event_info->MR_event_sll, 1,
                &base_sp, &base_curfr, &actual_level, &problem);
            if (actual_level != 1) {
                parent_filename = filename;
                parent_lineno = lineno;
            } else if (parent != NULL) {
                (void) MR_find_context(parent, &parent_filename,
                   &parent_lineno);
            }
        }

        msg = MR_trace_source_sync(&MR_trace_source_server, filename, lineno,
            parent_filename, parent_lineno, verbose);
        if (msg != NULL) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err, "mdb: %s.\n", msg);
        }
    }
}

void
MR_trace_maybe_close_source_window(MR_bool verbose)
{
    const char  *msg;

    if (MR_trace_source_server.server_name != NULL) {
        msg = MR_trace_source_close(&MR_trace_source_server, verbose);
        if (msg != NULL) {
            fflush(MR_mdb_out);
            fprintf(MR_mdb_err, "mdb: %s.\n", msg);
        }

        MR_free(MR_trace_source_server.server_name);
        MR_trace_source_server.server_name = NULL;
        MR_free(MR_trace_source_server.server_cmd);
        MR_trace_source_server.server_cmd = NULL;
    }
}

////////////////////////////////////////////////////////////////////////////

const char *const    MR_trace_print_cmd_args[] =
    { "-f", "-p", "-v", "--flat", "--pretty", "--verbose",
    "exception", "goal", "*", NULL };

// It is better to have a single completion where possible,
// so don't include `-d' here.

const char *const    MR_trace_stack_cmd_args[] =
    { "--detailed", NULL };

const char *const    MR_trace_view_cmd_args[] =
    { "-c", "-f", "-n", "-s", "-t", "-v", "-w", "-2",
    "--close", "--verbose", "--force", "--split-screen",
    "--window-command", "--server-command", "--server-name",
    "--timeout", NULL };

////////////////////////////////////////////////////////////////////////////

static struct MR_option MR_trace_detailed_opts[] =
{
    { "detailed",   MR_no_argument, NULL,   'd' },
    { NULL,         MR_no_argument, NULL,   0   }
};

static MR_bool
MR_trace_options_detailed(MR_bool *detailed, char ***words, int *word_count)
{
    int c;

    MR_optind = 0;
    while ((c = MR_getopt_long(*word_count, *words, "d",
        MR_trace_detailed_opts, NULL)) != EOF)
    {
        switch (c) {

            case 'd':
                *detailed = MR_TRUE;
                break;

            default:
                MR_trace_usage_cur_cmd();
                return MR_FALSE;
        }
    }

    *words = *words + MR_optind - 1;
    *word_count = *word_count - MR_optind + 1;
    return MR_TRUE;
}

static MR_bool
MR_trace_options_stack_trace(MR_bool *print_all, MR_bool *detailed,
    MR_SpecLineLimit *line_limit, MR_SpecLineLimit *clique_line_limit,
    MR_FrameLimit *frame_limit, char ***words, int *word_count)
{
    int c;

    MR_optind = 0;
    while ((c = MR_getopt_long(*word_count, *words, "ac:df:",
        MR_trace_detailed_opts, NULL)) != EOF)
    {
        switch (c) {
            case 'a':
                *print_all = MR_TRUE;
                *line_limit = 0;
                break;

            case 'c':
                if (! MR_trace_is_natural_number(MR_optarg, clique_line_limit))
                {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }
                *print_all = MR_FALSE;
                break;

            case 'd':
                *detailed = MR_TRUE;
                break;

            case 'f':
                if (! MR_trace_is_natural_number(MR_optarg, frame_limit)) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }
                break;

            default:
                MR_trace_usage_cur_cmd();
                return MR_FALSE;
        }
    }

    *words = *words + MR_optind - 1;
    *word_count = *word_count - MR_optind + 1;
    return MR_TRUE;
}

static struct MR_option MR_trace_print_opts[] =
{
    // Please keep the formatting options in sync with MR_trace_browse_opts.
    { "flat",       MR_no_argument,         NULL,   'f' },
    { "raw_pretty", MR_no_argument,         NULL,   'r' },
    { "verbose",    MR_no_argument,         NULL,   'v' },
    { "pretty",     MR_no_argument,         NULL,   'p' },
    { "max",        MR_required_argument,   NULL,   'm' },
    { NULL,         MR_no_argument,         NULL,   0   }
};

static MR_bool
MR_trace_options_print(MR_BrowseFormat *format,
    MR_Unsigned *max_printed_actions, MR_bool *set_max_printed_actions,
    char ***words, int *word_count)
{
    int c;

    *format = MR_BROWSE_DEFAULT_FORMAT;
    *max_printed_actions = -1;
    *set_max_printed_actions = MR_FALSE;
    MR_optind = 0;
    while ((c = MR_getopt_long(*word_count, *words, "frvpm:",
        MR_trace_print_opts, NULL)) != EOF)
    {
        switch (c) {

            case 'f':
                *format = MR_BROWSE_FORMAT_FLAT;
                break;

            case 'r':
                *format = MR_BROWSE_FORMAT_RAW_PRETTY;
                break;

            case 'v':
                *format = MR_BROWSE_FORMAT_VERBOSE;
                break;

            case 'p':
                *format = MR_BROWSE_FORMAT_PRETTY;
                break;

            case 'm':
                if (! MR_trace_is_natural_number(MR_optarg,
                    max_printed_actions))
                {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }
                if (*max_printed_actions == 0) {
                    // Printing a maximum of zero I/O actions
                    // does not make any sense.
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }
                *set_max_printed_actions = MR_TRUE;
                break;

            default:
                MR_trace_usage_cur_cmd();
                return MR_FALSE;
        }
    }

    *words = *words + MR_optind - 1;
    *word_count = *word_count - MR_optind + 1;
    return MR_TRUE;
}

static struct MR_option MR_trace_browse_opts[] =
{
    // Please keep the formatting options in sync with MR_trace_print_opts.
    { "flat",       MR_no_argument, NULL,   'f' },
    { "raw_pretty", MR_no_argument, NULL,   'r' },
    { "verbose",    MR_no_argument, NULL,   'v' },
    { "pretty",     MR_no_argument, NULL,   'p' },
    { "web",        MR_no_argument, NULL,   'w' },
    { NULL,         MR_no_argument, NULL,   0   }
};

static MR_bool
MR_trace_options_browse(MR_BrowseFormat *format, MR_bool *web,
    char ***words, int *word_count)
{
    int c;

    *format = MR_BROWSE_DEFAULT_FORMAT;
    *web = MR_FALSE;
    MR_optind = 0;
    while ((c = MR_getopt_long(*word_count, *words, "frvpw",
        MR_trace_browse_opts, NULL)) != EOF)
    {
        switch (c) {

            case 'f':
                *format = MR_BROWSE_FORMAT_FLAT;
                break;

            case 'r':
                *format = MR_BROWSE_FORMAT_RAW_PRETTY;
                break;

            case 'v':
                *format = MR_BROWSE_FORMAT_VERBOSE;
                break;

            case 'p':
                *format = MR_BROWSE_FORMAT_PRETTY;
                break;

            case 'w':
                *web = MR_TRUE;
                break;

            default:
                MR_trace_usage_cur_cmd();
                return MR_FALSE;
        }
    }

    *words = *words + MR_optind - 1;
    *word_count = *word_count - MR_optind + 1;
    return MR_TRUE;
}

static struct MR_option MR_trace_view_opts[] =
{
    { "close",          MR_no_argument,         NULL,   'c' },
    { "window-command", MR_required_argument,   NULL,   'w' },
    { "server-command", MR_required_argument,   NULL,   's' },
    { "server-name",    MR_required_argument,   NULL,   'n' },
    { "timeout",        MR_required_argument,   NULL,   't' },
    { "force",          MR_no_argument,         NULL,   'f' },
    { "verbose",        MR_no_argument,         NULL,   'v' },
    { "split-screen",   MR_no_argument,         NULL,   '2' },
    { NULL,             MR_no_argument,         NULL,   0   }
};

static MR_bool
MR_trace_options_view(const char **window_cmd, const char **server_cmd,
    const char **server_name, MR_Unsigned *timeout, MR_bool *force,
    MR_bool *verbose, MR_bool *split, MR_bool *close_window,
    char ***words, int *word_count)
{
    int c;
    MR_bool no_close = MR_FALSE;

    MR_optind = 0;
    while ((c = MR_getopt_long(*word_count, *words, "cw:s:n:t:fv2",
        MR_trace_view_opts, NULL)) != EOF)
    {
        // Option '-c' is mutually incompatible with '-f', '-t',
        // '-s', '-n', '-w' and '-2'.

        switch (c) {

            case 'c':
                if (no_close) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }

                *close_window = MR_TRUE;
                break;

            case 'w':
                if (*close_window) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }

                *window_cmd = MR_optarg;
                no_close = MR_TRUE;
                break;

            case 's':
                if (*close_window) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }

                *server_cmd = MR_optarg;
                no_close = MR_TRUE;
                break;

            case 'n':
                if (*close_window) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }

                *server_name = MR_optarg;
                no_close = MR_TRUE;
                break;

            case 't':
                if (*close_window ||
                    ! MR_trace_is_natural_number(MR_optarg, timeout))
                {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }

                no_close = MR_TRUE;
                break;

            case 'f':
                if (*close_window) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }

                *force = MR_TRUE;
                no_close = MR_TRUE;
                break;

            case 'v':
                *verbose = MR_TRUE;
                break;

            case '2':
                if (*close_window) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }

                *split = MR_TRUE;
                no_close = MR_TRUE;
                break;

            default:
                MR_trace_usage_cur_cmd();
                return MR_FALSE;
        }
    }

    *words = *words + MR_optind - 1;
    *word_count = *word_count - MR_optind + 1;
    return MR_TRUE;
}

static struct MR_option MR_trace_diff_opts[] =
{
    { "start",      MR_required_argument,   NULL,   's' },
    { "max",        MR_required_argument,   NULL,   'm' },
    { NULL,         MR_no_argument,         NULL,   0   }
};

static MR_bool
MR_trace_options_diff(MR_Unsigned *start, MR_Unsigned *max,
    char ***words, int *word_count)
{
    int c;

    MR_optind = 0;
    while ((c = MR_getopt_long(*word_count, *words, "m:s:",
        MR_trace_diff_opts, NULL)) != EOF)
    {
        switch (c) {

            case 'm':
                if (! MR_trace_is_natural_number(MR_optarg, max)) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }
                break;

            case 's':
                if (! MR_trace_is_natural_number(MR_optarg, start)) {
                    MR_trace_usage_cur_cmd();
                    return MR_FALSE;
                }
                break;

            default:
                MR_trace_usage_cur_cmd();
                return MR_FALSE;
        }
    }

    *words = *words + MR_optind - 1;
    *word_count = *word_count - MR_optind + 1;
    return MR_TRUE;
}

static struct MR_option MR_trace_dump_opts[] =
{
    { "quiet",          MR_no_argument,     NULL,   'q' },
    { "xml",            MR_no_argument,     NULL,   'x' },
    { "prettyprint",    MR_no_argument,     NULL,   'p' },
    { NULL,             MR_no_argument,     NULL,   0   }
};

static MR_bool
MR_trace_options_dump(MR_bool *quiet, MR_bool *xml, MR_bool *prettyprint,
    char ***words, int *word_count)
{
    int c;

    MR_optind = 0;
    while ((c = MR_getopt_long(*word_count, *words, "pqx",
        MR_trace_dump_opts, NULL)) != EOF)
    {
        switch (c) {

            case 'p':
                *prettyprint = MR_TRUE;
                break;

            case 'q':
                *quiet = MR_TRUE;
                break;

            case 'x':
                *xml = MR_TRUE;
                break;

            default:
                MR_trace_usage_cur_cmd();
                return MR_FALSE;
        }
    }

    *words = *words + MR_optind - 1;
    *word_count = *word_count - MR_optind + 1;
    return MR_TRUE;
}

////////////////////////////////////////////////////////////////////////////