/*
 * 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"
#include "submodule.h"
#include "dir.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;
}

/*
 * Has a file changed or has a submodule new commits or a dirty work tree?
 *
 * Return 1 when changes are detected, 0 otherwise. If the DIRTY_SUBMODULES
 * option is set, the caller does not only want to know if a submodule is
 * modified at all but wants to know all the conditions that are met (new
 * commits, untracked content and/or modified content).
 */
static int match_stat_with_submodule(struct diff_options *diffopt,
                                     const struct cache_entry *ce,
                                     struct stat *st, unsigned ce_option,
                                     unsigned *dirty_submodule)
{
        int changed = ce_match_stat(ce, st, ce_option);
        if (S_ISGITLINK(ce->ce_mode)) {
                unsigned orig_flags = diffopt->flags;
                if (!DIFF_OPT_TST(diffopt, OVERRIDE_SUBMODULE_CONFIG))
                        set_diffopt_flags_from_submodule_config(diffopt, ce->name);
                if (DIFF_OPT_TST(diffopt, IGNORE_SUBMODULES))
                        changed = 0;
                else if (!DIFF_OPT_TST(diffopt, IGNORE_DIRTY_SUBMODULES)
                    && (!changed || DIFF_OPT_TST(diffopt, DIRTY_SUBMODULES)))
                        *dirty_submodule = is_submodule_modified(ce->name, DIFF_OPT_TST(diffopt, IGNORE_UNTRACKED_IN_SUBMODULES));
                diffopt->flags = orig_flags;
        }
        return changed;
}

int run_diff_files(struct rev_info *revs, unsigned int option)
{
        int entries, i;
        int diff_unmerged_stage = revs->max_count;
        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++) {
                unsigned int oldmode, newmode;
                struct cache_entry *ce = active_cache[i];
                int changed;
                unsigned dirty_submodule = 0;
                const unsigned char *old_sha1, *new_sha1;

                if (diff_can_quit_early(&revs->diffopt))
                        break;

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

                if (ce_stage(ce)) {
                        struct combine_diff_path *dpath;
                        struct diff_filepair *pair;
                        unsigned int wt_mode = 0;
                        int num_compare_stages = 0;
                        size_t path_len;
                        struct stat st;

                        path_len = ce_namelen(ce);

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

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

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

                        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++;
                                        oidcpy(&dpath->parent[stage - 2].oid,
                                               &nce->oid);
                                        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.
                         */
                        pair = diff_unmerge(&revs->diffopt, ce->name);
                        if (wt_mode)
                                pair->two->mode = wt_mode;
                        if (ce_stage(ce) != diff_unmerged_stage)
                                continue;
                }

                if (ce_uptodate(ce) || ce_skip_worktree(ce))
                        continue;

                /* If CE_VALID is set, don't look at workdir for file removal */
                if (ce->ce_flags & CE_VALID) {
                        changed = 0;
                        newmode = ce->ce_mode;
                } else {
                        struct stat st;

                        changed = check_removed(ce, &st);
                        if (changed) {
                                if (changed < 0) {
                                        perror(ce->name);
                                        continue;
                                }
                                diff_addremove(&revs->diffopt, '-', ce->ce_mode,
                                               ce->oid.hash,
                                               !is_null_oid(&ce->oid),
                                               ce->name, 0);
                                continue;
                        }

                        changed = match_stat_with_submodule(&revs->diffopt, ce, &st,
                                                            ce_option, &dirty_submodule);
                        newmode = ce_mode_from_stat(ce, st.st_mode);
                }

                if (!changed && !dirty_submodule) {
                        ce_mark_uptodate(ce);
                        if (!DIFF_OPT_TST(&revs->diffopt, FIND_COPIES_HARDER))
                                continue;
                }
                oldmode = ce->ce_mode;
                old_sha1 = ce->oid.hash;
                new_sha1 = changed ? null_sha1 : ce->oid.hash;
                diff_change(&revs->diffopt, oldmode, newmode,
                            old_sha1, new_sha1,
                            !is_null_sha1(old_sha1),
                            !is_null_sha1(new_sha1),
                            ce->name, 0, dirty_submodule);

        }
        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,
                                 const struct cache_entry *ce,
                                 const unsigned char *sha1, int sha1_valid,
                                 unsigned int mode,
                                 unsigned dirty_submodule)
{
        diff_addremove(&revs->diffopt, prefix[0], mode,
                       sha1, sha1_valid, ce->name, dirty_submodule);
}

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

        if (!cached && !ce_uptodate(ce)) {
                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 = match_stat_with_submodule(diffopt, ce, &st,
                                                    0, dirty_submodule);
                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,
                          const struct cache_entry *new,
                          int cached, int match_missing)
{
        const unsigned char *sha1;
        unsigned int mode;
        unsigned dirty_submodule = 0;

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

        diff_index_show_file(revs, "+", new, sha1, !is_null_sha1(sha1), mode, dirty_submodule);
}

static int show_modified(struct rev_info *revs,
                         const struct cache_entry *old,
                         const struct cache_entry *new,
                         int report_missing,
                         int cached, int match_missing)
{
        unsigned int mode, oldmode;
        const unsigned char *sha1;
        unsigned dirty_submodule = 0;

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

        if (revs->combine_merges && !cached &&
            (hashcmp(sha1, old->oid.hash) || oidcmp(&old->oid, &new->oid))) {
                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;
                memcpy(p->path, new->name, pathlen);
                p->path[pathlen] = 0;
                p->mode = mode;
                oidclr(&p->oid);
                memset(p->parent, 0, 2 * sizeof(struct combine_diff_parent));
                p->parent[0].status = DIFF_STATUS_MODIFIED;
                p->parent[0].mode = new->ce_mode;
                oidcpy(&p->parent[0].oid, &new->oid);
                p->parent[1].status = DIFF_STATUS_MODIFIED;
                p->parent[1].mode = old->ce_mode;
                oidcpy(&p->parent[1].oid, &old->oid);
                show_combined_diff(p, 2, revs->dense_combined_merges, revs);
                free(p);
                return 0;
        }

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

        diff_change(&revs->diffopt, oldmode, mode,
                    old->oid.hash, sha1, 1, !is_null_sha1(sha1),
                    old->name, 0, dirty_submodule);
        return 0;
}

/*
 * 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,
                           const struct cache_entry *idx,
                           const struct cache_entry *tree)
{
        struct rev_info *revs = o->unpack_data;
        int match_missing, cached;

        /* if the entry is not checked out, don't examine work tree */
        cached = o->index_only ||
                (idx && ((idx->ce_flags & CE_VALID) || ce_skip_worktree(idx)));
        /*
         * 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".
         */
        match_missing = !revs->ignore_merges;

        if (cached && idx && ce_stage(idx)) {
                struct diff_filepair *pair;
                pair = diff_unmerge(&revs->diffopt, idx->name);
                if (tree)
                        fill_filespec(pair->one, tree->oid.hash, 1,
                                      tree->ce_mode);
                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->oid.hash, 1,
                                     tree->ce_mode, 0);
                return;
        }

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

/*
 * 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 advance o->pos to skip what we have already processed.
 *
 * 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(const struct cache_entry * const *src,
                       struct unpack_trees_options *o)
{
        const struct cache_entry *idx = src[0];
        const struct cache_entry *tree = src[1];
        struct rev_info *revs = o->unpack_data;

        /*
         * 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, NULL)) {
                do_oneway_diff(o, idx, tree);
                if (diff_can_quit_early(&revs->diffopt)) {
                        o->exiting_early = 1;
                        return -1;
                }
        }

        return 0;
}

static int diff_cache(struct rev_info *revs,
                      const unsigned char *tree_sha1,
                      const char *tree_name,
                      int cached)
{
        struct tree *tree;
        struct tree_desc t;
        struct unpack_trees_options opts;

        tree = parse_tree_indirect(tree_sha1);
        if (!tree)
                return error("bad tree object %s",
                             tree_name ? tree_name : sha1_to_hex(tree_sha1));
        memset(&opts, 0, sizeof(opts));
        opts.head_idx = 1;
        opts.index_only = cached;
        opts.diff_index_cached = (cached &&
                                  !DIFF_OPT_TST(&revs->diffopt, FIND_COPIES_HARDER));
        opts.merge = 1;
        opts.fn = oneway_diff;
        opts.unpack_data = revs;
        opts.src_index = &the_index;
        opts.dst_index = NULL;
        opts.pathspec = &revs->diffopt.pathspec;
        opts.pathspec->recursive = 1;

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

int run_diff_index(struct rev_info *revs, int cached)
{
        struct object_array_entry *ent;

        ent = revs->pending.objects;
        if (diff_cache(revs, ent->item->oid.hash, ent->name, cached))
                exit(128);

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

int do_diff_cache(const unsigned char *tree_sha1, struct diff_options *opt)
{
        struct rev_info revs;

        init_revisions(&revs, NULL);
        copy_pathspec(&revs.prune_data, &opt->pathspec);
        revs.diffopt = *opt;

        if (diff_cache(&revs, tree_sha1, NULL, 1))
                exit(128);
        return 0;
}

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

        init_revisions(&rev, NULL);
        memset(&opt, 0, sizeof(opt));
        opt.def = def;
        setup_revisions(0, NULL, &rev, &opt);
        DIFF_OPT_SET(&rev.diffopt, QUICK);
        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);
}