/*
 * Copyright (C) 2005 Junio C Hamano
 * Copyright (C) 2010 Google Inc.
 */
#include "cache.h"
#include "diff.h"
#include "diffcore.h"
#include "xdiff-interface.h"
#include "kwset.h"

typedef int (*pickaxe_fn)(mmfile_t *one, mmfile_t *two,
                          struct diff_options *o,
                          regex_t *regexp, kwset_t kws);

struct diffgrep_cb {
        regex_t *regexp;
        int hit;
};

static void diffgrep_consume(void *priv, char *line, unsigned long len)
{
        struct diffgrep_cb *data = priv;
        regmatch_t regmatch;
        int hold;

        if (line[0] != '+' && line[0] != '-')
                return;
        if (data->hit)
                /*
                 * NEEDSWORK: we should have a way to terminate the
                 * caller early.
                 */
                return;
        /* Yuck -- line ought to be "const char *"! */
        hold = line[len];
        line[len] = '\0';
        data->hit = !regexec(data->regexp, line + 1, 1, &regmatch, 0);
        line[len] = hold;
}

static int diff_grep(mmfile_t *one, mmfile_t *two,
                     struct diff_options *o,
                     regex_t *regexp, kwset_t kws)
{
        regmatch_t regmatch;
        struct diffgrep_cb ecbdata;
        xpparam_t xpp;
        xdemitconf_t xecfg;

        if (!one)
                return !regexec(regexp, two->ptr, 1, &regmatch, 0);
        if (!two)
                return !regexec(regexp, one->ptr, 1, &regmatch, 0);

        /*
         * We have both sides; need to run textual diff and see if
         * the pattern appears on added/deleted lines.
         */
        memset(&xpp, 0, sizeof(xpp));
        memset(&xecfg, 0, sizeof(xecfg));
        ecbdata.regexp = regexp;
        ecbdata.hit = 0;
        xecfg.ctxlen = o->context;
        xecfg.interhunkctxlen = o->interhunkcontext;
        xdi_diff_outf(one, two, diffgrep_consume, &ecbdata,
                      &xpp, &xecfg);
        return ecbdata.hit;
}

static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws)
{
        unsigned int cnt;
        unsigned long sz;
        const char *data;

        sz = mf->size;
        data = mf->ptr;
        cnt = 0;

        if (regexp) {
                regmatch_t regmatch;
                int flags = 0;

                assert(data[sz] == '\0');
                while (*data && !regexec(regexp, data, 1, &regmatch, flags)) {
                        flags |= REG_NOTBOL;
                        data += regmatch.rm_eo;
                        if (*data && regmatch.rm_so == regmatch.rm_eo)
                                data++;
                        cnt++;
                }

        } else { /* Classic exact string match */
                while (sz) {
                        struct kwsmatch kwsm;
                        size_t offset = kwsexec(kws, data, sz, &kwsm);
                        const char *found;
                        if (offset == -1)
                                break;
                        else
                                found = data + offset;
                        sz -= found - data + kwsm.size[0];
                        data = found + kwsm.size[0];
                        cnt++;
                }
        }
        return cnt;
}

static int has_changes(mmfile_t *one, mmfile_t *two,
                       struct diff_options *o,
                       regex_t *regexp, kwset_t kws)
{
        unsigned int one_contains = one ? contains(one, regexp, kws) : 0;
        unsigned int two_contains = two ? contains(two, regexp, kws) : 0;
        return one_contains != two_contains;
}

static int pickaxe_match(struct diff_filepair *p, struct diff_options *o,
                         regex_t *regexp, kwset_t kws, pickaxe_fn fn)
{
        struct userdiff_driver *textconv_one = NULL;
        struct userdiff_driver *textconv_two = NULL;
        mmfile_t mf1, mf2;
        int ret;

        if (!o->pickaxe[0])
                return 0;

        /* ignore unmerged */
        if (!DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two))
                return 0;

        if (DIFF_OPT_TST(o, ALLOW_TEXTCONV)) {
                textconv_one = get_textconv(p->one);
                textconv_two = get_textconv(p->two);
        }

        /*
         * If we have an unmodified pair, we know that the count will be the
         * same and don't even have to load the blobs. Unless textconv is in
         * play, _and_ we are using two different textconv filters (e.g.,
         * because a pair is an exact rename with different textconv attributes
         * for each side, which might generate different content).
         */
        if (textconv_one == textconv_two && diff_unmodified_pair(p))
                return 0;

        mf1.size = fill_textconv(textconv_one, p->one, &mf1.ptr);
        mf2.size = fill_textconv(textconv_two, p->two, &mf2.ptr);

        ret = fn(DIFF_FILE_VALID(p->one) ? &mf1 : NULL,
                 DIFF_FILE_VALID(p->two) ? &mf2 : NULL,
                 o, regexp, kws);

        if (textconv_one)
                free(mf1.ptr);
        if (textconv_two)
                free(mf2.ptr);
        diff_free_filespec_data(p->one);
        diff_free_filespec_data(p->two);

        return ret;
}

static void pickaxe(struct diff_queue_struct *q, struct diff_options *o,
                    regex_t *regexp, kwset_t kws, pickaxe_fn fn)
{
        int i;
        struct diff_queue_struct outq;

        DIFF_QUEUE_CLEAR(&outq);

        if (o->pickaxe_opts & DIFF_PICKAXE_ALL) {
                /* Showing the whole changeset if needle exists */
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (pickaxe_match(p, o, regexp, kws, fn))
                                return; /* do not munge the queue */
                }

                /*
                 * Otherwise we will clear the whole queue by copying
                 * the empty outq at the end of this function, but
                 * first clear the current entries in the queue.
                 */
                for (i = 0; i < q->nr; i++)
                        diff_free_filepair(q->queue[i]);
        } else {
                /* Showing only the filepairs that has the needle */
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (pickaxe_match(p, o, regexp, kws, fn))
                                diff_q(&outq, p);
                        else
                                diff_free_filepair(p);
                }
        }

        free(q->queue);
        *q = outq;
}

void diffcore_pickaxe(struct diff_options *o)
{
        const char *needle = o->pickaxe;
        int opts = o->pickaxe_opts;
        regex_t regex, *regexp = NULL;
        kwset_t kws = NULL;

        if (opts & (DIFF_PICKAXE_REGEX | DIFF_PICKAXE_KIND_G)) {
                int err;
                int cflags = REG_EXTENDED | REG_NEWLINE;
                if (DIFF_OPT_TST(o, PICKAXE_IGNORE_CASE))
                        cflags |= REG_ICASE;
                err = regcomp(&regex, needle, cflags);
                if (err) {
                        /* The POSIX.2 people are surely sick */
                        char errbuf[1024];
                        regerror(err, &regex, errbuf, 1024);
                        regfree(&regex);
                        die("invalid regex: %s", errbuf);
                }
                regexp = &regex;
        } else {
                kws = kwsalloc(DIFF_OPT_TST(o, PICKAXE_IGNORE_CASE)
                               ? tolower_trans_tbl : NULL);
                kwsincr(kws, needle, strlen(needle));
                kwsprep(kws);
        }

        /* Might want to warn when both S and G are on; I don't care... */
        pickaxe(&diff_queued_diff, o, regexp, kws,
                (opts & DIFF_PICKAXE_KIND_G) ? diff_grep : has_changes);

        if (regexp)
                regfree(regexp);
        else
                kwsfree(kws);
        return;
}