/*
 * builtin-help.c
 *
 * Builtin help command
 */
#include "perf.h"
#include "util/cache.h"
#include "builtin.h"
#include "util/exec_cmd.h"
#include "common-cmds.h"
#include "util/parse-options.h"
#include "util/run-command.h"
#include "util/help.h"
#include "util/debug.h"

static struct man_viewer_list {
        struct man_viewer_list *next;
        char name[FLEX_ARRAY];
} *man_viewer_list;

static struct man_viewer_info_list {
        struct man_viewer_info_list *next;
        const char *info;
        char name[FLEX_ARRAY];
} *man_viewer_info_list;

enum help_format {
        HELP_FORMAT_NONE,
        HELP_FORMAT_MAN,
        HELP_FORMAT_INFO,
        HELP_FORMAT_WEB,
};

static enum help_format parse_help_format(const char *format)
{
        if (!strcmp(format, "man"))
                return HELP_FORMAT_MAN;
        if (!strcmp(format, "info"))
                return HELP_FORMAT_INFO;
        if (!strcmp(format, "web") || !strcmp(format, "html"))
                return HELP_FORMAT_WEB;

        pr_err("unrecognized help format '%s'", format);
        return HELP_FORMAT_NONE;
}

static const char *get_man_viewer_info(const char *name)
{
        struct man_viewer_info_list *viewer;

        for (viewer = man_viewer_info_list; viewer; viewer = viewer->next) {
                if (!strcasecmp(name, viewer->name))
                        return viewer->info;
        }
        return NULL;
}

static int check_emacsclient_version(void)
{
        struct strbuf buffer = STRBUF_INIT;
        struct child_process ec_process;
        const char *argv_ec[] = { "emacsclient", "--version", NULL };
        int version;

        /* emacsclient prints its version number on stderr */
        memset(&ec_process, 0, sizeof(ec_process));
        ec_process.argv = argv_ec;
        ec_process.err = -1;
        ec_process.stdout_to_stderr = 1;
        if (start_command(&ec_process)) {
                fprintf(stderr, "Failed to start emacsclient.\n");
                return -1;
        }
        strbuf_read(&buffer, ec_process.err, 20);
        close(ec_process.err);

        /*
         * Don't bother checking return value, because "emacsclient --version"
         * seems to always exits with code 1.
         */
        finish_command(&ec_process);

        if (prefixcmp(buffer.buf, "emacsclient")) {
                fprintf(stderr, "Failed to parse emacsclient version.\n");
                strbuf_release(&buffer);
                return -1;
        }

        strbuf_remove(&buffer, 0, strlen("emacsclient"));
        version = atoi(buffer.buf);

        if (version < 22) {
                fprintf(stderr,
                        "emacsclient version '%d' too old (< 22).\n",
                        version);
                strbuf_release(&buffer);
                return -1;
        }

        strbuf_release(&buffer);
        return 0;
}

static void exec_woman_emacs(const char *path, const char *page)
{
        char sbuf[STRERR_BUFSIZE];

        if (!check_emacsclient_version()) {
                /* This works only with emacsclient version >= 22. */
                struct strbuf man_page = STRBUF_INIT;

                if (!path)
                        path = "emacsclient";
                strbuf_addf(&man_page, "(woman \"%s\")", page);
                execlp(path, "emacsclient", "-e", man_page.buf, NULL);
                warning("failed to exec '%s': %s", path,
                        strerror_r(errno, sbuf, sizeof(sbuf)));
        }
}

static void exec_man_konqueror(const char *path, const char *page)
{
        const char *display = getenv("DISPLAY");

        if (display && *display) {
                struct strbuf man_page = STRBUF_INIT;
                const char *filename = "kfmclient";
                char sbuf[STRERR_BUFSIZE];

                /* It's simpler to launch konqueror using kfmclient. */
                if (path) {
                        const char *file = strrchr(path, '/');
                        if (file && !strcmp(file + 1, "konqueror")) {
                                char *new = strdup(path);
                                char *dest = strrchr(new, '/');

                                /* strlen("konqueror") == strlen("kfmclient") */
                                strcpy(dest + 1, "kfmclient");
                                path = new;
                        }
                        if (file)
                                filename = file;
                } else
                        path = "kfmclient";
                strbuf_addf(&man_page, "man:%s(1)", page);
                execlp(path, filename, "newTab", man_page.buf, NULL);
                warning("failed to exec '%s': %s", path,
                        strerror_r(errno, sbuf, sizeof(sbuf)));
        }
}

static void exec_man_man(const char *path, const char *page)
{
        char sbuf[STRERR_BUFSIZE];

        if (!path)
                path = "man";
        execlp(path, "man", page, NULL);
        warning("failed to exec '%s': %s", path,
                strerror_r(errno, sbuf, sizeof(sbuf)));
}

static void exec_man_cmd(const char *cmd, const char *page)
{
        struct strbuf shell_cmd = STRBUF_INIT;
        char sbuf[STRERR_BUFSIZE];

        strbuf_addf(&shell_cmd, "%s %s", cmd, page);
        execl("/bin/sh", "sh", "-c", shell_cmd.buf, NULL);
        warning("failed to exec '%s': %s", cmd,
                strerror_r(errno, sbuf, sizeof(sbuf)));
}

static void add_man_viewer(const char *name)
{
        struct man_viewer_list **p = &man_viewer_list;
        size_t len = strlen(name);

        while (*p)
                p = &((*p)->next);
        *p = zalloc(sizeof(**p) + len + 1);
        strncpy((*p)->name, name, len);
}

static int supported_man_viewer(const char *name, size_t len)
{
        return (!strncasecmp("man", name, len) ||
                !strncasecmp("woman", name, len) ||
                !strncasecmp("konqueror", name, len));
}

static void do_add_man_viewer_info(const char *name,
                                   size_t len,
                                   const char *value)
{
        struct man_viewer_info_list *new = zalloc(sizeof(*new) + len + 1);

        strncpy(new->name, name, len);
        new->info = strdup(value);
        new->next = man_viewer_info_list;
        man_viewer_info_list = new;
}

static int add_man_viewer_path(const char *name,
                               size_t len,
                               const char *value)
{
        if (supported_man_viewer(name, len))
                do_add_man_viewer_info(name, len, value);
        else
                warning("'%s': path for unsupported man viewer.\n"
                        "Please consider using 'man.<tool>.cmd' instead.",
                        name);

        return 0;
}

static int add_man_viewer_cmd(const char *name,
                              size_t len,
                              const char *value)
{
        if (supported_man_viewer(name, len))
                warning("'%s': cmd for supported man viewer.\n"
                        "Please consider using 'man.<tool>.path' instead.",
                        name);
        else
                do_add_man_viewer_info(name, len, value);

        return 0;
}

static int add_man_viewer_info(const char *var, const char *value)
{
        const char *name = var + 4;
        const char *subkey = strrchr(name, '.');

        if (!subkey)
                return error("Config with no key for man viewer: %s", name);

        if (!strcmp(subkey, ".path")) {
                if (!value)
                        return config_error_nonbool(var);
                return add_man_viewer_path(name, subkey - name, value);
        }
        if (!strcmp(subkey, ".cmd")) {
                if (!value)
                        return config_error_nonbool(var);
                return add_man_viewer_cmd(name, subkey - name, value);
        }

        warning("'%s': unsupported man viewer sub key.", subkey);
        return 0;
}

static int perf_help_config(const char *var, const char *value, void *cb)
{
        enum help_format *help_formatp = cb;

        if (!strcmp(var, "help.format")) {
                if (!value)
                        return config_error_nonbool(var);
                *help_formatp = parse_help_format(value);
                if (*help_formatp == HELP_FORMAT_NONE)
                        return -1;
                return 0;
        }
        if (!strcmp(var, "man.viewer")) {
                if (!value)
                        return config_error_nonbool(var);
                add_man_viewer(value);
                return 0;
        }
        if (!prefixcmp(var, "man."))
                return add_man_viewer_info(var, value);

        return perf_default_config(var, value, cb);
}

static struct cmdnames main_cmds, other_cmds;

void list_common_cmds_help(void)
{
        unsigned int i, longest = 0;

        for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
                if (longest < strlen(common_cmds[i].name))
                        longest = strlen(common_cmds[i].name);
        }

        puts(" The most commonly used perf commands are:");
        for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
                printf("   %-*s   ", longest, common_cmds[i].name);
                puts(common_cmds[i].help);
        }
}

static int is_perf_command(const char *s)
{
        return is_in_cmdlist(&main_cmds, s) ||
                is_in_cmdlist(&other_cmds, s);
}

static const char *prepend(const char *prefix, const char *cmd)
{
        size_t pre_len = strlen(prefix);
        size_t cmd_len = strlen(cmd);
        char *p = malloc(pre_len + cmd_len + 1);
        memcpy(p, prefix, pre_len);
        strcpy(p + pre_len, cmd);
        return p;
}

static const char *cmd_to_page(const char *perf_cmd)
{
        if (!perf_cmd)
                return "perf";
        else if (!prefixcmp(perf_cmd, "perf"))
                return perf_cmd;
        else
                return prepend("perf-", perf_cmd);
}

static void setup_man_path(void)
{
        struct strbuf new_path = STRBUF_INIT;
        const char *old_path = getenv("MANPATH");

        /* We should always put ':' after our path. If there is no
         * old_path, the ':' at the end will let 'man' to try
         * system-wide paths after ours to find the manual page. If
         * there is old_path, we need ':' as delimiter. */
        strbuf_addstr(&new_path, system_path(PERF_MAN_PATH));
        strbuf_addch(&new_path, ':');
        if (old_path)
                strbuf_addstr(&new_path, old_path);

        setenv("MANPATH", new_path.buf, 1);

        strbuf_release(&new_path);
}

static void exec_viewer(const char *name, const char *page)
{
        const char *info = get_man_viewer_info(name);

        if (!strcasecmp(name, "man"))
                exec_man_man(info, page);
        else if (!strcasecmp(name, "woman"))
                exec_woman_emacs(info, page);
        else if (!strcasecmp(name, "konqueror"))
                exec_man_konqueror(info, page);
        else if (info)
                exec_man_cmd(info, page);
        else
                warning("'%s': unknown man viewer.", name);
}

static int show_man_page(const char *perf_cmd)
{
        struct man_viewer_list *viewer;
        const char *page = cmd_to_page(perf_cmd);
        const char *fallback = getenv("PERF_MAN_VIEWER");

        setup_man_path();
        for (viewer = man_viewer_list; viewer; viewer = viewer->next)
                exec_viewer(viewer->name, page); /* will return when unable */

        if (fallback)
                exec_viewer(fallback, page);
        exec_viewer("man", page);

        pr_err("no man viewer handled the request");
        return -1;
}

static int show_info_page(const char *perf_cmd)
{
        const char *page = cmd_to_page(perf_cmd);
        setenv("INFOPATH", system_path(PERF_INFO_PATH), 1);
        execlp("info", "info", "perfman", page, NULL);
        return -1;
}

static int get_html_page_path(struct strbuf *page_path, const char *page)
{
        struct stat st;
        const char *html_path = system_path(PERF_HTML_PATH);

        /* Check that we have a perf documentation directory. */
        if (stat(mkpath("%s/perf.html", html_path), &st)
            || !S_ISREG(st.st_mode)) {
                pr_err("'%s': not a documentation directory.", html_path);
                return -1;
        }

        strbuf_init(page_path, 0);
        strbuf_addf(page_path, "%s/%s.html", html_path, page);

        return 0;
}

/*
 * If open_html is not defined in a platform-specific way (see for
 * example compat/mingw.h), we use the script web--browse to display
 * HTML.
 */
#ifndef open_html
static void open_html(const char *path)
{
        execl_perf_cmd("web--browse", "-c", "help.browser", path, NULL);
}
#endif

static int show_html_page(const char *perf_cmd)
{
        const char *page = cmd_to_page(perf_cmd);
        struct strbuf page_path; /* it leaks but we exec bellow */

        if (get_html_page_path(&page_path, page) != 0)
                return -1;

        open_html(page_path.buf);

        return 0;
}

int cmd_help(int argc, const char **argv, const char *prefix __maybe_unused)
{
        bool show_all = false;
        enum help_format help_format = HELP_FORMAT_MAN;
        struct option builtin_help_options[] = {
        OPT_BOOLEAN('a', "all", &show_all, "print all available commands"),
        OPT_SET_UINT('m', "man", &help_format, "show man page", HELP_FORMAT_MAN),
        OPT_SET_UINT('w', "web", &help_format, "show manual in web browser",
                        HELP_FORMAT_WEB),
        OPT_SET_UINT('i', "info", &help_format, "show info page",
                        HELP_FORMAT_INFO),
        OPT_END(),
        };
        const char * const builtin_help_usage[] = {
                "perf help [--all] [--man|--web|--info] [command]",
                NULL
        };
        const char *alias;
        int rc = 0;

        load_command_list("perf-", &main_cmds, &other_cmds);

        perf_config(perf_help_config, &help_format);

        argc = parse_options(argc, argv, builtin_help_options,
                        builtin_help_usage, 0);

        if (show_all) {
                printf("\n usage: %s\n\n", perf_usage_string);
                list_commands("perf commands", &main_cmds, &other_cmds);
                printf(" %s\n\n", perf_more_info_string);
                return 0;
        }

        if (!argv[0]) {
                printf("\n usage: %s\n\n", perf_usage_string);
                list_common_cmds_help();
                printf("\n %s\n\n", perf_more_info_string);
                return 0;
        }

        alias = alias_lookup(argv[0]);
        if (alias && !is_perf_command(argv[0])) {
                printf("`perf %s' is aliased to `%s'\n", argv[0], alias);
                return 0;
        }

        switch (help_format) {
        case HELP_FORMAT_MAN:
                rc = show_man_page(argv[0]);
                break;
        case HELP_FORMAT_INFO:
                rc = show_info_page(argv[0]);
                break;
        case HELP_FORMAT_WEB:
                rc = show_html_page(argv[0]);
                break;
        case HELP_FORMAT_NONE:
                /* fall-through */
        default:
                rc = -1;
                break;
        }

        return rc;
}