/*
 * Builtin "git diff"
 *
 * Copyright (c) 2006 Junio C Hamano
 */
#include "cache.h"
#include "color.h"
#include "commit.h"
#include "blob.h"
#include "tag.h"
#include "diff.h"
#include "diffcore.h"
#include "revision.h"
#include "log-tree.h"
#include "builtin.h"

struct blobinfo {
        unsigned char sha1[20];
        const char *name;
        unsigned mode;
};

static const char builtin_diff_usage[] =
"git diff <options> <rev>{0,2} -- <path>*";

static void stuff_change(struct diff_options *opt,
                         unsigned old_mode, unsigned new_mode,
                         const unsigned char *old_sha1,
                         const unsigned char *new_sha1,
                         const char *old_name,
                         const char *new_name)
{
        struct diff_filespec *one, *two;

        if (!is_null_sha1(old_sha1) && !is_null_sha1(new_sha1) &&
            !hashcmp(old_sha1, new_sha1) && (old_mode == new_mode))
                return;

        if (DIFF_OPT_TST(opt, REVERSE_DIFF)) {
                unsigned tmp;
                const unsigned char *tmp_u;
                const char *tmp_c;
                tmp = old_mode; old_mode = new_mode; new_mode = tmp;
                tmp_u = old_sha1; old_sha1 = new_sha1; new_sha1 = tmp_u;
                tmp_c = old_name; old_name = new_name; new_name = tmp_c;
        }

        if (opt->prefix &&
            (strncmp(old_name, opt->prefix, opt->prefix_length) ||
             strncmp(new_name, opt->prefix, opt->prefix_length)))
                return;

        one = alloc_filespec(old_name);
        two = alloc_filespec(new_name);
        fill_filespec(one, old_sha1, old_mode);
        fill_filespec(two, new_sha1, new_mode);

        diff_queue(&diff_queued_diff, one, two);
}

static int builtin_diff_b_f(struct rev_info *revs,
                            int argc, const char **argv,
                            struct blobinfo *blob,
                            const char *path)
{
        /* Blob vs file in the working tree*/
        struct stat st;

        if (argc > 1)
                usage(builtin_diff_usage);

        if (lstat(path, &st))
                die("'%s': %s", path, strerror(errno));
        if (!(S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)))
                die("'%s': not a regular file or symlink", path);

        if (blob[0].mode == S_IFINVALID)
                blob[0].mode = canon_mode(st.st_mode);

        stuff_change(&revs->diffopt,
                     blob[0].mode, canon_mode(st.st_mode),
                     blob[0].sha1, null_sha1,
                     path, path);
        diffcore_std(&revs->diffopt);
        diff_flush(&revs->diffopt);
        return 0;
}

static int builtin_diff_blobs(struct rev_info *revs,
                              int argc, const char **argv,
                              struct blobinfo *blob)
{
        unsigned mode = canon_mode(S_IFREG | 0644);

        if (argc > 1)
                usage(builtin_diff_usage);

        if (blob[0].mode == S_IFINVALID)
                blob[0].mode = mode;

        if (blob[1].mode == S_IFINVALID)
                blob[1].mode = mode;

        stuff_change(&revs->diffopt,
                     blob[0].mode, blob[1].mode,
                     blob[0].sha1, blob[1].sha1,
                     blob[0].name, blob[1].name);
        diffcore_std(&revs->diffopt);
        diff_flush(&revs->diffopt);
        return 0;
}

static int builtin_diff_index(struct rev_info *revs,
                              int argc, const char **argv)
{
        int cached = 0;
        while (1 < argc) {
                const char *arg = argv[1];
                if (!strcmp(arg, "--cached"))
                        cached = 1;
                else
                        usage(builtin_diff_usage);
                argv++; argc--;
        }
        if (!cached)
                setup_work_tree();
        /*
         * Make sure there is one revision (i.e. pending object),
         * and there is no revision filtering parameters.
         */
        if (revs->pending.nr != 1 ||
            revs->max_count != -1 || revs->min_age != -1 ||
            revs->max_age != -1)
                usage(builtin_diff_usage);
        if (read_cache() < 0) {
                perror("read_cache");
                return -1;
        }
        return run_diff_index(revs, cached);
}

static int builtin_diff_tree(struct rev_info *revs,
                             int argc, const char **argv,
                             struct object_array_entry *ent)
{
        const unsigned char *(sha1[2]);
        int swap = 0;

        if (argc > 1)
                usage(builtin_diff_usage);

        /* We saw two trees, ent[0] and ent[1].
         * if ent[1] is uninteresting, they are swapped
         */
        if (ent[1].item->flags & UNINTERESTING)
                swap = 1;
        sha1[swap] = ent[0].item->sha1;
        sha1[1-swap] = ent[1].item->sha1;
        diff_tree_sha1(sha1[0], sha1[1], "", &revs->diffopt);
        log_tree_diff_flush(revs);
        return 0;
}

static int builtin_diff_combined(struct rev_info *revs,
                                 int argc, const char **argv,
                                 struct object_array_entry *ent,
                                 int ents)
{
        const unsigned char (*parent)[20];
        int i;

        if (argc > 1)
                usage(builtin_diff_usage);

        if (!revs->dense_combined_merges && !revs->combine_merges)
                revs->dense_combined_merges = revs->combine_merges = 1;
        parent = xmalloc(ents * sizeof(*parent));
        /* Again, the revs are all reverse */
        for (i = 0; i < ents; i++)
                hashcpy((unsigned char *)(parent + i),
                        ent[ents - 1 - i].item->sha1);
        diff_tree_combined(parent[0], parent + 1, ents - 1,
                           revs->dense_combined_merges, revs);
        return 0;
}

static void refresh_index_quietly(void)
{
        struct lock_file *lock_file;
        int fd;

        lock_file = xcalloc(1, sizeof(struct lock_file));
        fd = hold_locked_index(lock_file, 0);
        if (fd < 0)
                return;
        discard_cache();
        read_cache();
        refresh_cache(REFRESH_QUIET|REFRESH_UNMERGED);

        if (active_cache_changed &&
            !write_cache(fd, active_cache, active_nr))
                commit_locked_index(lock_file);

        rollback_lock_file(lock_file);
}

static int builtin_diff_files(struct rev_info *revs, int argc, const char **argv)
{
        int result;
        unsigned int options = 0;

        while (1 < argc && argv[1][0] == '-') {
                if (!strcmp(argv[1], "--base"))
                        revs->max_count = 1;
                else if (!strcmp(argv[1], "--ours"))
                        revs->max_count = 2;
                else if (!strcmp(argv[1], "--theirs"))
                        revs->max_count = 3;
                else if (!strcmp(argv[1], "-q"))
                        options |= DIFF_SILENT_ON_REMOVED;
                else
                        return error("invalid option: %s", argv[1]);
                argv++; argc--;
        }

        /*
         * "diff --base" should not combine merges because it was not
         * asked to.  "diff -c" should not densify (if the user wants
         * dense one, --cc can be explicitly asked for, or just rely
         * on the default).
         */
        if (revs->max_count == -1 && !revs->combine_merges &&
            (revs->diffopt.output_format & DIFF_FORMAT_PATCH))
                revs->combine_merges = revs->dense_combined_merges = 1;

        setup_work_tree();
        if (read_cache() < 0) {
                perror("read_cache");
                return -1;
        }
        result = run_diff_files(revs, options);
        return diff_result_code(&revs->diffopt, result);
}

int cmd_diff(int argc, const char **argv, const char *prefix)
{
        int i;
        struct rev_info rev;
        struct object_array_entry ent[100];
        int ents = 0, blobs = 0, paths = 0;
        const char *path = NULL;
        struct blobinfo blob[2];
        int nongit;
        int result = 0;

        /*
         * We could get N tree-ish in the rev.pending_objects list.
         * Also there could be M blobs there, and P pathspecs.
         *
         * N=0, M=0:
         *      cache vs files (diff-files)
         * N=0, M=2:
         *      compare two random blobs.  P must be zero.
         * N=0, M=1, P=1:
         *      compare a blob with a working tree file.
         *
         * N=1, M=0:
         *      tree vs cache (diff-index --cached)
         *
         * N=2, M=0:
         *      tree vs tree (diff-tree)
         *
         * N=0, M=0, P=2:
         *      compare two filesystem entities (aka --no-index).
         *
         * Other cases are errors.
         */

        prefix = setup_git_directory_gently(&nongit);
        git_config(git_diff_ui_config, NULL);

        if (diff_use_color_default == -1)
                diff_use_color_default = git_use_color_default;

        init_revisions(&rev, prefix);

        /* If this is a no-index diff, just run it and exit there. */
        diff_no_index(&rev, argc, argv, nongit, prefix);

        /* Otherwise, we are doing the usual "git" diff */
        rev.diffopt.skip_stat_unmatch = !!diff_auto_refresh_index;

        /* Default to let external be used */
        DIFF_OPT_SET(&rev.diffopt, ALLOW_EXTERNAL);

        if (nongit)
                die("Not a git repository");
        argc = setup_revisions(argc, argv, &rev, NULL);
        if (!rev.diffopt.output_format) {
                rev.diffopt.output_format = DIFF_FORMAT_PATCH;
                if (diff_setup_done(&rev.diffopt) < 0)
                        die("diff_setup_done failed");
        }

        DIFF_OPT_SET(&rev.diffopt, RECURSIVE);

        /*
         * If the user asked for our exit code then don't start a
         * pager or we would end up reporting its exit code instead.
         */
        if (!DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS) &&
            check_pager_config("diff") != 0)
                setup_pager();

        /*
         * Do we have --cached and not have a pending object, then
         * default to HEAD by hand.  Eek.
         */
        if (!rev.pending.nr) {
                int i;
                for (i = 1; i < argc; i++) {
                        const char *arg = argv[i];
                        if (!strcmp(arg, "--"))
                                break;
                        else if (!strcmp(arg, "--cached")) {
                                add_head_to_pending(&rev);
                                if (!rev.pending.nr)
                                        die("No HEAD commit to compare with (yet)");
                                break;
                        }
                }
        }

        for (i = 0; i < rev.pending.nr; i++) {
                struct object_array_entry *list = rev.pending.objects+i;
                struct object *obj = list->item;
                const char *name = list->name;
                int flags = (obj->flags & UNINTERESTING);
                if (!obj->parsed)
                        obj = parse_object(obj->sha1);
                obj = deref_tag(obj, NULL, 0);
                if (!obj)
                        die("invalid object '%s' given.", name);
                if (obj->type == OBJ_COMMIT)
                        obj = &((struct commit *)obj)->tree->object;
                if (obj->type == OBJ_TREE) {
                        if (ARRAY_SIZE(ent) <= ents)
                                die("more than %d trees given: '%s'",
                                    (int) ARRAY_SIZE(ent), name);
                        obj->flags |= flags;
                        ent[ents].item = obj;
                        ent[ents].name = name;
                        ents++;
                        continue;
                }
                if (obj->type == OBJ_BLOB) {
                        if (2 <= blobs)
                                die("more than two blobs given: '%s'", name);
                        hashcpy(blob[blobs].sha1, obj->sha1);
                        blob[blobs].name = name;
                        blob[blobs].mode = list->mode;
                        blobs++;
                        continue;

                }
                die("unhandled object '%s' given.", name);
        }
        if (rev.prune_data) {
                const char **pathspec = rev.prune_data;
                while (*pathspec) {
                        if (!path)
                                path = *pathspec;
                        paths++;
                        pathspec++;
                }
        }

        /*
         * Now, do the arguments look reasonable?
         */
        if (!ents) {
                switch (blobs) {
                case 0:
                        result = builtin_diff_files(&rev, argc, argv);
                        break;
                case 1:
                        if (paths != 1)
                                usage(builtin_diff_usage);
                        result = builtin_diff_b_f(&rev, argc, argv, blob, path);
                        break;
                case 2:
                        if (paths)
                                usage(builtin_diff_usage);
                        result = builtin_diff_blobs(&rev, argc, argv, blob);
                        break;
                default:
                        usage(builtin_diff_usage);
                }
        }
        else if (blobs)
                usage(builtin_diff_usage);
        else if (ents == 1)
                result = builtin_diff_index(&rev, argc, argv);
        else if (ents == 2)
                result = builtin_diff_tree(&rev, argc, argv, ent);
        else if ((ents == 3) && (ent[0].item->flags & UNINTERESTING)) {
                /* diff A...B where there is one sane merge base between
                 * A and B.  We have ent[0] == merge-base, ent[1] == A,
                 * and ent[2] == B.  Show diff between the base and B.
                 */
                ent[1] = ent[2];
                result = builtin_diff_tree(&rev, argc, argv, ent);
        }
        else
                result = builtin_diff_combined(&rev, argc, argv,
                                             ent, ents);
        result = diff_result_code(&rev.diffopt, result);
        if (1 < rev.diffopt.skip_stat_unmatch)
                refresh_index_quietly();
        return result;
}