#include "git-compat-util.h"
#include "line-range.h"
#include "xdiff-interface.h"
#include "strbuf.h"
#include "userdiff.h"

/*
 * Parse one item in the -L option
 */
static const char *parse_loc(const char *spec, nth_line_fn_t nth_line,
                             void *data, long lines, long begin, long *ret)
{
        char *term;
        const char *line;
        long num;
        int reg_error;
        regex_t regexp;
        regmatch_t match[1];

        /* Allow "-L <something>,+20" to mean starting at <something>
         * for 20 lines, or "-L <something>,-5" for 5 lines ending at
         * <something>.
         */
        if (1 < begin && (spec[0] == '+' || spec[0] == '-')) {
                num = strtol(spec + 1, &term, 10);
                if (term != spec + 1) {
                        if (!ret)
                                return term;
                        if (spec[0] == '-')
                                num = 0 - num;
                        if (0 < num)
                                *ret = begin + num - 2;
                        else if (!num)
                                *ret = begin;
                        else
                                *ret = begin + num;
                        return term;
                }
                return spec;
        }
        num = strtol(spec, &term, 10);
        if (term != spec) {
                if (ret)
                        *ret = num;
                return term;
        }
        if (spec[0] != '/')
                return spec;

        /* it could be a regexp of form /.../ */
        for (term = (char *) spec + 1; *term && *term != '/'; term++) {
                if (*term == '\\')
                        term++;
        }
        if (*term != '/')
                return spec;

        /* in the scan-only case we are not interested in the regex */
        if (!ret)
                return term+1;

        /* try [spec+1 .. term-1] as regexp */
        *term = 0;
        begin--; /* input is in human terms */
        line = nth_line(data, begin);

        if (!(reg_error = regcomp(&regexp, spec + 1, REG_NEWLINE)) &&
            !(reg_error = regexec(&regexp, line, 1, match, 0))) {
                const char *cp = line + match[0].rm_so;
                const char *nline;

                while (begin++ < lines) {
                        nline = nth_line(data, begin);
                        if (line <= cp && cp < nline)
                                break;
                        line = nline;
                }
                *ret = begin;
                regfree(&regexp);
                *term++ = '/';
                return term;
        }
        else {
                char errbuf[1024];
                regerror(reg_error, &regexp, errbuf, 1024);
                die("-L parameter '%s': %s", spec + 1, errbuf);
        }
}

static int match_funcname(xdemitconf_t *xecfg, const char *bol, const char *eol)
{
        if (xecfg) {
                char buf[1];
                return xecfg->find_func(bol, eol - bol, buf, 1,
                                        xecfg->find_func_priv) >= 0;
        }

        if (bol == eol)
                return 0;
        if (isalpha(*bol) || *bol == '_' || *bol == '$')
                return 1;
        return 0;
}

static const char *find_funcname_matching_regexp(xdemitconf_t *xecfg, const char *start,
                                                 regex_t *regexp)
{
        int reg_error;
        regmatch_t match[1];
        while (1) {
                const char *bol, *eol;
                reg_error = regexec(regexp, start, 1, match, 0);
                if (reg_error == REG_NOMATCH)
                        return NULL;
                else if (reg_error) {
                        char errbuf[1024];
                        regerror(reg_error, regexp, errbuf, 1024);
                        die("-L parameter: regexec() failed: %s", errbuf);
                }
                /* determine extent of line matched */
                bol = start+match[0].rm_so;
                eol = start+match[0].rm_eo;
                while (bol > start && *bol != '\n')
                        bol--;
                if (*bol == '\n')
                        bol++;
                while (*eol && *eol != '\n')
                        eol++;
                if (*eol == '\n')
                        eol++;
                /* is it a funcname line? */
                if (match_funcname(xecfg, (char*) bol, (char*) eol))
                        return bol;
                start = eol;
        }
}

static const char *parse_range_funcname(const char *arg, nth_line_fn_t nth_line_cb,
                                        void *cb_data, long lines, long *begin, long *end,
                                        const char *path)
{
        char *pattern;
        const char *term;
        struct userdiff_driver *drv;
        xdemitconf_t *xecfg = NULL;
        const char *start;
        const char *p;
        int reg_error;
        regex_t regexp;

        assert(*arg == ':');
        term = arg+1;
        while (*term && *term != ':') {
                if (*term == '\\' && *(term+1))
                        term++;
                term++;
        }
        if (term == arg+1)
                return NULL;
        if (!begin) /* skip_range_arg case */
                return term;

        pattern = xstrndup(arg+1, term-(arg+1));

        start = nth_line_cb(cb_data, 0);

        drv = userdiff_find_by_path(path);
        if (drv && drv->funcname.pattern) {
                const struct userdiff_funcname *pe = &drv->funcname;
                xecfg = xcalloc(1, sizeof(*xecfg));
                xdiff_set_find_func(xecfg, pe->pattern, pe->cflags);
        }

        reg_error = regcomp(&regexp, pattern, REG_NEWLINE);
        if (reg_error) {
                char errbuf[1024];
                regerror(reg_error, &regexp, errbuf, 1024);
                die("-L parameter '%s': %s", pattern, errbuf);
        }

        p = find_funcname_matching_regexp(xecfg, (char*) start, &regexp);
        if (!p)
                die("-L parameter '%s': no match", pattern);
        *begin = 0;
        while (p > nth_line_cb(cb_data, *begin))
                (*begin)++;

        if (*begin >= lines)
                die("-L parameter '%s' matches at EOF", pattern);

        *end = *begin+1;
        while (*end < lines) {
                const char *bol = nth_line_cb(cb_data, *end);
                const char *eol = nth_line_cb(cb_data, *end+1);
                if (match_funcname(xecfg, bol, eol))
                        break;
                (*end)++;
        }

        regfree(&regexp);
        free(xecfg);
        free(pattern);

        /* compensate for 1-based numbering */
        (*begin)++;

        return term;
}

int parse_range_arg(const char *arg, nth_line_fn_t nth_line_cb,
                    void *cb_data, long lines, long *begin, long *end,
                    const char *path)
{
        if (*arg == ':') {
                arg = parse_range_funcname(arg, nth_line_cb, cb_data, lines, begin, end, path);
                if (!arg || *arg)
                        return -1;
                return 0;
        }

        arg = parse_loc(arg, nth_line_cb, cb_data, lines, 1, begin);

        if (*arg == ',')
                arg = parse_loc(arg + 1, nth_line_cb, cb_data, lines, *begin + 1, end);

        if (*arg)
                return -1;

        return 0;
}

const char *skip_range_arg(const char *arg)
{
        if (*arg == ':')
                return parse_range_funcname(arg, NULL, NULL, 0, NULL, NULL, NULL);

        arg = parse_loc(arg, NULL, NULL, 0, -1, NULL);

        if (*arg == ',')
                arg = parse_loc(arg+1, NULL, NULL, 0, 0, NULL);

        return arg;
}