/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include "cache.h"
#include "quote.h"
#include "commit.h"
#include "diff.h"
#include "diffcore.h"
#include "revision.h"
#include "cache-tree.h"
#include "unpack-trees.h"
#include "refs.h"

/*
 * diff-files
 */

/*
 * Has the work tree entity been removed?
 *
 * Return 1 if it was removed from the work tree, 0 if an entity to be
 * compared with the cache entry ce still exists (the latter includes
 * the case where a directory that is not a submodule repository
 * exists for ce that is a submodule -- it is a submodule that is not
 * checked out).  Return negative for an error.
 */
static int check_removed(const struct cache_entry *ce, struct stat *st)
{
        if (lstat(ce->name, st) < 0) {
                if (errno != ENOENT && errno != ENOTDIR)
                        return -1;
                return 1;
        }
        if (has_symlink_leading_path(ce->name, ce_namelen(ce)))
                return 1;
        if (S_ISDIR(st->st_mode)) {
                unsigned char sub[20];

                /*
                 * If ce is already a gitlink, we can have a plain
                 * directory (i.e. the submodule is not checked out),
                 * or a checked out submodule.  Either case this is not
                 * a case where something was removed from the work tree,
                 * so we will return 0.
                 *
                 * Otherwise, if the directory is not a submodule
                 * repository, that means ce which was a blob turned into
                 * a directory --- the blob was removed!
                 */
                if (!S_ISGITLINK(ce->ce_mode) &&
                    resolve_gitlink_ref(ce->name, "HEAD", sub))
                        return 1;
        }
        return 0;
}

int run_diff_files(struct rev_info *revs, unsigned int option)
{
        int entries, i;
        int diff_unmerged_stage = revs->max_count;
        int silent_on_removed = option & DIFF_SILENT_ON_REMOVED;
        unsigned ce_option = ((option & DIFF_RACY_IS_MODIFIED)
                              ? CE_MATCH_RACY_IS_DIRTY : 0);

        diff_set_mnemonic_prefix(&revs->diffopt, "i/", "w/");

        if (diff_unmerged_stage < 0)
                diff_unmerged_stage = 2;
        entries = active_nr;
        for (i = 0; i < entries; i++) {
                struct stat st;
                unsigned int oldmode, newmode;
                struct cache_entry *ce = active_cache[i];
                int changed;

                if (DIFF_OPT_TST(&revs->diffopt, QUIET) &&
                        DIFF_OPT_TST(&revs->diffopt, HAS_CHANGES))
                        break;

                if (!ce_path_match(ce, revs->prune_data))
                        continue;

                if (ce_stage(ce)) {
                        struct combine_diff_path *dpath;
                        int num_compare_stages = 0;
                        size_t path_len;

                        path_len = ce_namelen(ce);

                        dpath = xmalloc(combine_diff_path_size(5, path_len));
                        dpath->path = (char *) &(dpath->parent[5]);

                        dpath->next = NULL;
                        dpath->len = path_len;
                        memcpy(dpath->path, ce->name, path_len);
                        dpath->path[path_len] = '\0';
                        hashclr(dpath->sha1);
                        memset(&(dpath->parent[0]), 0,
                               sizeof(struct combine_diff_parent)*5);

                        changed = check_removed(ce, &st);
                        if (!changed)
                                dpath->mode = ce_mode_from_stat(ce, st.st_mode);
                        else {
                                if (changed < 0) {
                                        perror(ce->name);
                                        continue;
                                }
                                if (silent_on_removed)
                                        continue;
                        }

                        while (i < entries) {
                                struct cache_entry *nce = active_cache[i];
                                int stage;

                                if (strcmp(ce->name, nce->name))
                                        break;

                                /* Stage #2 (ours) is the first parent,
                                 * stage #3 (theirs) is the second.
                                 */
                                stage = ce_stage(nce);
                                if (2 <= stage) {
                                        int mode = nce->ce_mode;
                                        num_compare_stages++;
                                        hashcpy(dpath->parent[stage-2].sha1, nce->sha1);
                                        dpath->parent[stage-2].mode = ce_mode_from_stat(nce, mode);
                                        dpath->parent[stage-2].status =
                                                DIFF_STATUS_MODIFIED;
                                }

                                /* diff against the proper unmerged stage */
                                if (stage == diff_unmerged_stage)
                                        ce = nce;
                                i++;
                        }
                        /*
                         * Compensate for loop update
                         */
                        i--;

                        if (revs->combine_merges && num_compare_stages == 2) {
                                show_combined_diff(dpath, 2,
                                                   revs->dense_combined_merges,
                                                   revs);
                                free(dpath);
                                continue;
                        }
                        free(dpath);
                        dpath = NULL;

                        /*
                         * Show the diff for the 'ce' if we found the one
                         * from the desired stage.
                         */
                        diff_unmerge(&revs->diffopt, ce->name, 0, null_sha1);
                        if (ce_stage(ce) != diff_unmerged_stage)
                                continue;
                }

                if (ce_uptodate(ce))
                        continue;

                changed = check_removed(ce, &st);
                if (changed) {
                        if (changed < 0) {
                                perror(ce->name);
                                continue;
                        }
                        if (silent_on_removed)
                                continue;
                        diff_addremove(&revs->diffopt, '-', ce->ce_mode,
                                       ce->sha1, ce->name);
                        continue;
                }
                changed = ce_match_stat(ce, &st, ce_option);
                if (!changed) {
                        ce_mark_uptodate(ce);
                        if (!DIFF_OPT_TST(&revs->diffopt, FIND_COPIES_HARDER))
                                continue;
                }
                oldmode = ce->ce_mode;
                newmode = ce_mode_from_stat(ce, st.st_mode);
                diff_change(&revs->diffopt, oldmode, newmode,
                            ce->sha1, (changed ? null_sha1 : ce->sha1),
                            ce->name);

        }
        diffcore_std(&revs->diffopt);
        diff_flush(&revs->diffopt);
        return 0;
}

/*
 * diff-index
 */

/* A file entry went away or appeared */
static void diff_index_show_file(struct rev_info *revs,
                                 const char *prefix,
                                 struct cache_entry *ce,
                                 const unsigned char *sha1, unsigned int mode)
{
        diff_addremove(&revs->diffopt, prefix[0], mode,
                       sha1, ce->name);
}

static int get_stat_data(struct cache_entry *ce,
                         const unsigned char **sha1p,
                         unsigned int *modep,
                         int cached, int match_missing)
{
        const unsigned char *sha1 = ce->sha1;
        unsigned int mode = ce->ce_mode;

        if (!cached) {
                int changed;
                struct stat st;
                changed = check_removed(ce, &st);
                if (changed < 0)
                        return -1;
                else if (changed) {
                        if (match_missing) {
                                *sha1p = sha1;
                                *modep = mode;
                                return 0;
                        }
                        return -1;
                }
                changed = ce_match_stat(ce, &st, 0);
                if (changed) {
                        mode = ce_mode_from_stat(ce, st.st_mode);
                        sha1 = null_sha1;
                }
        }

        *sha1p = sha1;
        *modep = mode;
        return 0;
}

static void show_new_file(struct rev_info *revs,
                          struct cache_entry *new,
                          int cached, int match_missing)
{
        const unsigned char *sha1;
        unsigned int mode;

        /*
         * New file in the index: it might actually be different in
         * the working copy.
         */
        if (get_stat_data(new, &sha1, &mode, cached, match_missing) < 0)
                return;

        diff_index_show_file(revs, "+", new, sha1, mode);
}

static int show_modified(struct rev_info *revs,
                         struct cache_entry *old,
                         struct cache_entry *new,
                         int report_missing,
                         int cached, int match_missing)
{
        unsigned int mode, oldmode;
        const unsigned char *sha1;

        if (get_stat_data(new, &sha1, &mode, cached, match_missing) < 0) {
                if (report_missing)
                        diff_index_show_file(revs, "-", old,
                                             old->sha1, old->ce_mode);
                return -1;
        }

        if (revs->combine_merges && !cached &&
            (hashcmp(sha1, old->sha1) || hashcmp(old->sha1, new->sha1))) {
                struct combine_diff_path *p;
                int pathlen = ce_namelen(new);

                p = xmalloc(combine_diff_path_size(2, pathlen));
                p->path = (char *) &p->parent[2];
                p->next = NULL;
                p->len = pathlen;
                memcpy(p->path, new->name, pathlen);
                p->path[pathlen] = 0;
                p->mode = mode;
                hashclr(p->sha1);
                memset(p->parent, 0, 2 * sizeof(struct combine_diff_parent));
                p->parent[0].status = DIFF_STATUS_MODIFIED;
                p->parent[0].mode = new->ce_mode;
                hashcpy(p->parent[0].sha1, new->sha1);
                p->parent[1].status = DIFF_STATUS_MODIFIED;
                p->parent[1].mode = old->ce_mode;
                hashcpy(p->parent[1].sha1, old->sha1);
                show_combined_diff(p, 2, revs->dense_combined_merges, revs);
                free(p);
                return 0;
        }

        oldmode = old->ce_mode;
        if (mode == oldmode && !hashcmp(sha1, old->sha1) &&
            !DIFF_OPT_TST(&revs->diffopt, FIND_COPIES_HARDER))
                return 0;

        diff_change(&revs->diffopt, oldmode, mode,
                    old->sha1, sha1, old->name);
        return 0;
}

/*
 * This turns all merge entries into "stage 3". That guarantees that
 * when we read in the new tree (into "stage 1"), we won't lose sight
 * of the fact that we had unmerged entries.
 */
static void mark_merge_entries(void)
{
        int i;
        for (i = 0; i < active_nr; i++) {
                struct cache_entry *ce = active_cache[i];
                if (!ce_stage(ce))
                        continue;
                ce->ce_flags |= CE_STAGEMASK;
        }
}

/*
 * This gets a mix of an existing index and a tree, one pathname entry
 * at a time. The index entry may be a single stage-0 one, but it could
 * also be multiple unmerged entries (in which case idx_pos/idx_nr will
 * give you the position and number of entries in the index).
 */
static void do_oneway_diff(struct unpack_trees_options *o,
        struct cache_entry *idx,
        struct cache_entry *tree)
{
        struct rev_info *revs = o->unpack_data;
        int match_missing, cached;

        /*
         * Backward compatibility wart - "diff-index -m" does
         * not mean "do not ignore merges", but "match_missing".
         *
         * But with the revision flag parsing, that's found in
         * "!revs->ignore_merges".
         */
        cached = o->index_only;
        match_missing = !revs->ignore_merges;

        if (cached && idx && ce_stage(idx)) {
                if (tree)
                        diff_unmerge(&revs->diffopt, idx->name, idx->ce_mode, idx->sha1);
                return;
        }

        /*
         * Something added to the tree?
         */
        if (!tree) {
                show_new_file(revs, idx, cached, match_missing);
                return;
        }

        /*
         * Something removed from the tree?
         */
        if (!idx) {
                diff_index_show_file(revs, "-", tree, tree->sha1, tree->ce_mode);
                return;
        }

        /* Show difference between old and new */
        show_modified(revs, tree, idx, 1, cached, match_missing);
}

static inline void skip_same_name(struct cache_entry *ce, struct unpack_trees_options *o)
{
        int len = ce_namelen(ce);
        const struct index_state *index = o->src_index;

        while (o->pos < index->cache_nr) {
                struct cache_entry *next = index->cache[o->pos];
                if (len != ce_namelen(next))
                        break;
                if (memcmp(ce->name, next->name, len))
                        break;
                o->pos++;
        }
}

/*
 * The unpack_trees() interface is designed for merging, so
 * the different source entries are designed primarily for
 * the source trees, with the old index being really mainly
 * used for being replaced by the result.
 *
 * For diffing, the index is more important, and we only have a
 * single tree.
 *
 * We're supposed to return how many index entries we want to skip.
 *
 * This wrapper makes it all more readable, and takes care of all
 * the fairly complex unpack_trees() semantic requirements, including
 * the skipping, the path matching, the type conflict cases etc.
 */
static int oneway_diff(struct cache_entry **src, struct unpack_trees_options *o)
{
        struct cache_entry *idx = src[0];
        struct cache_entry *tree = src[1];
        struct rev_info *revs = o->unpack_data;

        if (idx && ce_stage(idx))
                skip_same_name(idx, o);

        /*
         * Unpack-trees generates a DF/conflict entry if
         * there was a directory in the index and a tree
         * in the tree. From a diff standpoint, that's a
         * delete of the tree and a create of the file.
         */
        if (tree == o->df_conflict_entry)
                tree = NULL;

        if (ce_path_match(idx ? idx : tree, revs->prune_data))
                do_oneway_diff(o, idx, tree);

        return 0;
}

int run_diff_index(struct rev_info *revs, int cached)
{
        struct object *ent;
        struct tree *tree;
        const char *tree_name;
        struct unpack_trees_options opts;
        struct tree_desc t;

        mark_merge_entries();

        ent = revs->pending.objects[0].item;
        tree_name = revs->pending.objects[0].name;
        tree = parse_tree_indirect(ent->sha1);
        if (!tree)
                return error("bad tree object %s", tree_name);

        memset(&opts, 0, sizeof(opts));
        opts.head_idx = 1;
        opts.index_only = cached;
        opts.merge = 1;
        opts.fn = oneway_diff;
        opts.unpack_data = revs;
        opts.src_index = &the_index;
        opts.dst_index = NULL;

        init_tree_desc(&t, tree->buffer, tree->size);
        if (unpack_trees(1, &t, &opts))
                exit(128);

        diff_set_mnemonic_prefix(&revs->diffopt, "c/", cached ? "i/" : "w/");
        diffcore_std(&revs->diffopt);
        diff_flush(&revs->diffopt);
        return 0;
}

int do_diff_cache(const unsigned char *tree_sha1, struct diff_options *opt)
{
        struct tree *tree;
        struct rev_info revs;
        int i;
        struct cache_entry **dst;
        struct cache_entry *last = NULL;
        struct unpack_trees_options opts;
        struct tree_desc t;

        /*
         * This is used by git-blame to run diff-cache internally;
         * it potentially needs to repeatedly run this, so we will
         * start by removing the higher order entries the last round
         * left behind.
         */
        dst = active_cache;
        for (i = 0; i < active_nr; i++) {
                struct cache_entry *ce = active_cache[i];
                if (ce_stage(ce)) {
                        if (last && !strcmp(ce->name, last->name))
                                continue;
                        cache_tree_invalidate_path(active_cache_tree,
                                                   ce->name);
                        last = ce;
                        ce->ce_flags |= CE_REMOVE;
                }
                *dst++ = ce;
        }
        active_nr = dst - active_cache;

        init_revisions(&revs, NULL);
        revs.prune_data = opt->paths;
        tree = parse_tree_indirect(tree_sha1);
        if (!tree)
                die("bad tree object %s", sha1_to_hex(tree_sha1));

        memset(&opts, 0, sizeof(opts));
        opts.head_idx = 1;
        opts.index_only = 1;
        opts.merge = 1;
        opts.fn = oneway_diff;
        opts.unpack_data = &revs;
        opts.src_index = &the_index;
        opts.dst_index = &the_index;

        init_tree_desc(&t, tree->buffer, tree->size);
        if (unpack_trees(1, &t, &opts))
                exit(128);
        return 0;
}

int index_differs_from(const char *def, int diff_flags)
{
        struct rev_info rev;

        init_revisions(&rev, NULL);
        setup_revisions(0, NULL, &rev, def);
        DIFF_OPT_SET(&rev.diffopt, QUIET);
        DIFF_OPT_SET(&rev.diffopt, EXIT_WITH_STATUS);
        rev.diffopt.flags |= diff_flags;
        run_diff_index(&rev, 1);
        if (rev.pending.alloc)
                free(rev.pending.objects);
        return (DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0);
}