/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 */

#include "cache.h"
#include "object.h"
#include "tree.h"
#include "tree-walk.h"
#include "cache-tree.h"
#include "unpack-trees.h"
#include "dir.h"
#include "builtin.h"

static int nr_trees;
static struct tree *trees[MAX_UNPACK_TREES];

static int list_tree(unsigned char *sha1)
{
        struct tree *tree;

        if (nr_trees >= MAX_UNPACK_TREES)
                die("I cannot read more than %d trees", MAX_UNPACK_TREES);
        tree = parse_tree_indirect(sha1);
        if (!tree)
                return -1;
        trees[nr_trees++] = tree;
        return 0;
}

static const char read_tree_usage[] = "git read-tree (<sha> | [[-m [--trivial] [--aggressive] | --reset | --prefix=<prefix>] [-u | -i]] [--exclude-per-directory=<gitignore>] [--index-output=<file>] <sha1> [<sha2> [<sha3>]])";

static struct lock_file lock_file;

int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
{
        int i, newfd, stage = 0;
        unsigned char sha1[20];
        struct tree_desc t[MAX_UNPACK_TREES];
        struct unpack_trees_options opts;

        memset(&opts, 0, sizeof(opts));
        opts.head_idx = -1;
        opts.src_index = &the_index;
        opts.dst_index = &the_index;

        git_config(git_default_config, NULL);

        newfd = hold_locked_index(&lock_file, 1);

        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];

                /* "-u" means "update", meaning that a merge will update
                 * the working tree.
                 */
                if (!strcmp(arg, "-u")) {
                        opts.update = 1;
                        continue;
                }

                if (!strcmp(arg, "-v")) {
                        opts.verbose_update = 1;
                        continue;
                }

                /* "-i" means "index only", meaning that a merge will
                 * not even look at the working tree.
                 */
                if (!strcmp(arg, "-i")) {
                        opts.index_only = 1;
                        continue;
                }

                if (!prefixcmp(arg, "--index-output=")) {
                        set_alternate_index_output(arg + 15);
                        continue;
                }

                /* "--prefix=<subdirectory>/" means keep the current index
                 *  entries and put the entries from the tree under the
                 * given subdirectory.
                 */
                if (!prefixcmp(arg, "--prefix=")) {
                        if (stage || opts.merge || opts.prefix)
                                usage(read_tree_usage);
                        opts.prefix = arg + 9;
                        opts.merge = 1;
                        stage = 1;
                        if (read_cache_unmerged())
                                die("you need to resolve your current index first");
                        continue;
                }

                /* This differs from "-m" in that we'll silently ignore
                 * unmerged entries and overwrite working tree files that
                 * correspond to them.
                 */
                if (!strcmp(arg, "--reset")) {
                        if (stage || opts.merge || opts.prefix)
                                usage(read_tree_usage);
                        opts.reset = 1;
                        opts.merge = 1;
                        stage = 1;
                        read_cache_unmerged();
                        continue;
                }

                if (!strcmp(arg, "--trivial")) {
                        opts.trivial_merges_only = 1;
                        continue;
                }

                if (!strcmp(arg, "--aggressive")) {
                        opts.aggressive = 1;
                        continue;
                }

                /* "-m" stands for "merge", meaning we start in stage 1 */
                if (!strcmp(arg, "-m")) {
                        if (stage || opts.merge || opts.prefix)
                                usage(read_tree_usage);
                        if (read_cache_unmerged())
                                die("you need to resolve your current index first");
                        stage = 1;
                        opts.merge = 1;
                        continue;
                }

                if (!prefixcmp(arg, "--exclude-per-directory=")) {
                        struct dir_struct *dir;

                        if (opts.dir)
                                die("more than one --exclude-per-directory are given.");

                        dir = xcalloc(1, sizeof(*opts.dir));
                        dir->show_ignored = 1;
                        dir->exclude_per_dir = arg + 24;
                        opts.dir = dir;
                        /* We do not need to nor want to do read-directory
                         * here; we are merely interested in reusing the
                         * per directory ignore stack mechanism.
                         */
                        continue;
                }

                /* using -u and -i at the same time makes no sense */
                if (1 < opts.index_only + opts.update)
                        usage(read_tree_usage);

                if (get_sha1(arg, sha1))
                        die("Not a valid object name %s", arg);
                if (list_tree(sha1) < 0)
                        die("failed to unpack tree object %s", arg);
                stage++;
        }
        if ((opts.update||opts.index_only) && !opts.merge)
                usage(read_tree_usage);
        if ((opts.dir && !opts.update))
                die("--exclude-per-directory is meaningless unless -u");
        if (opts.merge && !opts.index_only)
                setup_work_tree();

        if (opts.merge) {
                if (stage < 2)
                        die("just how do you expect me to merge %d trees?", stage-1);
                switch (stage - 1) {
                case 1:
                        opts.fn = opts.prefix ? bind_merge : oneway_merge;
                        break;
                case 2:
                        opts.fn = twoway_merge;
                        opts.initial_checkout = is_cache_unborn();
                        break;
                case 3:
                default:
                        opts.fn = threeway_merge;
                        break;
                }

                if (stage - 1 >= 3)
                        opts.head_idx = stage - 2;
                else
                        opts.head_idx = 1;
        }

        cache_tree_free(&active_cache_tree);
        for (i = 0; i < nr_trees; i++) {
                struct tree *tree = trees[i];
                parse_tree(tree);
                init_tree_desc(t+i, tree->buffer, tree->size);
        }
        if (unpack_trees(nr_trees, t, &opts))
                return 128;

        /*
         * When reading only one tree (either the most basic form,
         * "-m ent" or "--reset ent" form), we can obtain a fully
         * valid cache-tree because the index must match exactly
         * what came from the tree.
         *
         * The same holds true if we are switching between two trees
         * using read-tree -m A B.  The index must match B after that.
         */
        if (nr_trees == 1 && !opts.prefix)
                prime_cache_tree(&active_cache_tree, trees[0]);
        else if (nr_trees == 2 && opts.merge)
                prime_cache_tree(&active_cache_tree, trees[1]);

        if (write_cache(newfd, active_cache, active_nr) ||
            commit_locked_index(&lock_file))
                die("unable to write new index file");
        return 0;
}