#include "cache.h"
#include "range-diff.h"
#include "string-list.h"
#include "run-command.h"
#include "argv-array.h"
#include "hashmap.h"
#include "xdiff-interface.h"
#include "linear-assignment.h"

struct patch_util {
        /* For the search for an exact match */
        struct hashmap_entry e;
        const char *diff, *patch;

        int i, shown;
        int diffsize;
        size_t diff_offset;
        /* the index of the matching item in the other branch, or -1 */
        int matching;
        struct object_id oid;
};

/*
 * Reads the patches into a string list, with the `util` field being populated
 * as struct object_id (will need to be free()d).
 */
static int read_patches(const char *range, struct string_list *list)
{
        struct child_process cp = CHILD_PROCESS_INIT;
        FILE *in;
        struct strbuf buf = STRBUF_INIT, line = STRBUF_INIT;
        struct patch_util *util = NULL;
        int in_header = 1;

        argv_array_pushl(&cp.args, "log", "--no-color", "-p", "--no-merges",
                        "--reverse", "--date-order", "--decorate=no",
                        "--no-abbrev-commit", range,
                        NULL);
        cp.out = -1;
        cp.no_stdin = 1;
        cp.git_cmd = 1;

        if (start_command(&cp))
                return error_errno(_("could not start `log`"));
        in = fdopen(cp.out, "r");
        if (!in) {
                error_errno(_("could not read `log` output"));
                finish_command(&cp);
                return -1;
        }

        while (strbuf_getline(&line, in) != EOF) {
                const char *p;

                if (skip_prefix(line.buf, "commit ", &p)) {
                        if (util) {
                                string_list_append(list, buf.buf)->util = util;
                                strbuf_reset(&buf);
                        }
                        util = xcalloc(sizeof(*util), 1);
                        if (get_oid(p, &util->oid)) {
                                error(_("could not parse commit '%s'"), p);
                                free(util);
                                string_list_clear(list, 1);
                                strbuf_release(&buf);
                                strbuf_release(&line);
                                fclose(in);
                                finish_command(&cp);
                                return -1;
                        }
                        util->matching = -1;
                        in_header = 1;
                        continue;
                }

                if (starts_with(line.buf, "diff --git")) {
                        in_header = 0;
                        strbuf_addch(&buf, '\n');
                        if (!util->diff_offset)
                                util->diff_offset = buf.len;
                        strbuf_addbuf(&buf, &line);
                } else if (in_header) {
                        if (starts_with(line.buf, "Author: ")) {
                                strbuf_addbuf(&buf, &line);
                                strbuf_addstr(&buf, "\n\n");
                        } else if (starts_with(line.buf, "    ")) {
                                strbuf_addbuf(&buf, &line);
                                strbuf_addch(&buf, '\n');
                        }
                        continue;
                } else if (starts_with(line.buf, "@@ "))
                        strbuf_addstr(&buf, "@@");
                else if (!line.buf[0] || starts_with(line.buf, "index "))
                        /*
                         * A completely blank (not ' \n', which is context)
                         * line is not valid in a diff.  We skip it
                         * silently, because this neatly handles the blank
                         * separator line between commits in git-log
                         * output.
                         *
                         * We also want to ignore the diff's `index` lines
                         * because they contain exact blob hashes in which
                         * we are not interested.
                         */
                        continue;
                else
                        strbuf_addbuf(&buf, &line);

                strbuf_addch(&buf, '\n');
                util->diffsize++;
        }
        fclose(in);
        strbuf_release(&line);

        if (util)
                string_list_append(list, buf.buf)->util = util;
        strbuf_release(&buf);

        if (finish_command(&cp))
                return -1;

        return 0;
}

static int patch_util_cmp(const void *dummy, const struct patch_util *a,
                     const struct patch_util *b, const char *keydata)
{
        return strcmp(a->diff, keydata ? keydata : b->diff);
}

static void find_exact_matches(struct string_list *a, struct string_list *b)
{
        struct hashmap map;
        int i;

        hashmap_init(&map, (hashmap_cmp_fn)patch_util_cmp, NULL, 0);

        /* First, add the patches of a to a hash map */
        for (i = 0; i < a->nr; i++) {
                struct patch_util *util = a->items[i].util;

                util->i = i;
                util->patch = a->items[i].string;
                util->diff = util->patch + util->diff_offset;
                hashmap_entry_init(util, strhash(util->diff));
                hashmap_add(&map, util);
        }

        /* Now try to find exact matches in b */
        for (i = 0; i < b->nr; i++) {
                struct patch_util *util = b->items[i].util, *other;

                util->i = i;
                util->patch = b->items[i].string;
                util->diff = util->patch + util->diff_offset;
                hashmap_entry_init(util, strhash(util->diff));
                other = hashmap_remove(&map, util, NULL);
                if (other) {
                        if (other->matching >= 0)
                                BUG("already assigned!");

                        other->matching = i;
                        util->matching = other->i;
                }
        }

        hashmap_free(&map, 0);
}

static void diffsize_consume(void *data, char *line, unsigned long len)
{
        (*(int *)data)++;
}

static int diffsize(const char *a, const char *b)
{
        xpparam_t pp = { 0 };
        xdemitconf_t cfg = { 0 };
        mmfile_t mf1, mf2;
        int count = 0;

        mf1.ptr = (char *)a;
        mf1.size = strlen(a);
        mf2.ptr = (char *)b;
        mf2.size = strlen(b);

        cfg.ctxlen = 3;
        if (!xdi_diff_outf(&mf1, &mf2, diffsize_consume, &count, &pp, &cfg))
                return count;

        error(_("failed to generate diff"));
        return COST_MAX;
}

static void get_correspondences(struct string_list *a, struct string_list *b,
                                int creation_factor)
{
        int n = a->nr + b->nr;
        int *cost, c, *a2b, *b2a;
        int i, j;

        ALLOC_ARRAY(cost, st_mult(n, n));
        ALLOC_ARRAY(a2b, n);
        ALLOC_ARRAY(b2a, n);

        for (i = 0; i < a->nr; i++) {
                struct patch_util *a_util = a->items[i].util;

                for (j = 0; j < b->nr; j++) {
                        struct patch_util *b_util = b->items[j].util;

                        if (a_util->matching == j)
                                c = 0;
                        else if (a_util->matching < 0 && b_util->matching < 0)
                                c = diffsize(a_util->diff, b_util->diff);
                        else
                                c = COST_MAX;
                        cost[i + n * j] = c;
                }

                c = a_util->matching < 0 ?
                        a_util->diffsize * creation_factor / 100 : COST_MAX;
                for (j = b->nr; j < n; j++)
                        cost[i + n * j] = c;
        }

        for (j = 0; j < b->nr; j++) {
                struct patch_util *util = b->items[j].util;

                c = util->matching < 0 ?
                        util->diffsize * creation_factor / 100 : COST_MAX;
                for (i = a->nr; i < n; i++)
                        cost[i + n * j] = c;
        }

        for (i = a->nr; i < n; i++)
                for (j = b->nr; j < n; j++)
                        cost[i + n * j] = 0;

        compute_assignment(n, n, cost, a2b, b2a);

        for (i = 0; i < a->nr; i++)
                if (a2b[i] >= 0 && a2b[i] < b->nr) {
                        struct patch_util *a_util = a->items[i].util;
                        struct patch_util *b_util = b->items[a2b[i]].util;

                        a_util->matching = a2b[i];
                        b_util->matching = i;
                }

        free(cost);
        free(a2b);
        free(b2a);
}

static const char *short_oid(struct patch_util *util)
{
        return find_unique_abbrev(&util->oid, DEFAULT_ABBREV);
}

static void output(struct string_list *a, struct string_list *b)
{
        int i = 0, j = 0;

        /*
         * We assume the user is really more interested in the second argument
         * ("newer" version). To that end, we print the output in the order of
         * the RHS (the `b` parameter). To put the LHS (the `a` parameter)
         * commits that are no longer in the RHS into a good place, we place
         * them once we have shown all of their predecessors in the LHS.
         */

        while (i < a->nr || j < b->nr) {
                struct patch_util *a_util, *b_util;
                a_util = i < a->nr ? a->items[i].util : NULL;
                b_util = j < b->nr ? b->items[j].util : NULL;

                /* Skip all the already-shown commits from the LHS. */
                while (i < a->nr && a_util->shown)
                        a_util = ++i < a->nr ? a->items[i].util : NULL;

                /* Show unmatched LHS commit whose predecessors were shown. */
                if (i < a->nr && a_util->matching < 0) {
                        printf("%d: %s < -: --------\n",
                               i + 1, short_oid(a_util));
                        i++;
                        continue;
                }

                /* Show unmatched RHS commits. */
                while (j < b->nr && b_util->matching < 0) {
                        printf("-: -------- > %d: %s\n",
                               j + 1, short_oid(b_util));
                        b_util = ++j < b->nr ? b->items[j].util : NULL;
                }

                /* Show matching LHS/RHS pair. */
                if (j < b->nr) {
                        a_util = a->items[b_util->matching].util;
                        printf("%d: %s ! %d: %s\n",
                               b_util->matching + 1, short_oid(a_util),
                               j + 1, short_oid(b_util));
                        a_util->shown = 1;
                        j++;
                }
        }
}

int show_range_diff(const char *range1, const char *range2,
                    int creation_factor)
{
        int res = 0;

        struct string_list branch1 = STRING_LIST_INIT_DUP;
        struct string_list branch2 = STRING_LIST_INIT_DUP;

        if (read_patches(range1, &branch1))
                res = error(_("could not parse log for '%s'"), range1);
        if (!res && read_patches(range2, &branch2))
                res = error(_("could not parse log for '%s'"), range2);

        if (!res) {
                find_exact_matches(&branch1, &branch2);
                get_correspondences(&branch1, &branch2, creation_factor);
                output(&branch1, &branch2);
        }

        string_list_clear(&branch1, 1);
        string_list_clear(&branch2, 1);

        return res;
}