/*
 * 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"
#include "parse-options.h"
#include "resolve-undo.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 * const read_tree_usage[] = {
        "git read-tree [[-m [--trivial] [--aggressive] | --reset | --prefix=<prefix>] [-u [--exclude-per-directory=<gitignore>] | -i]]  [--index-output=<file>] <tree-ish1> [<tree-ish2> [<tree-ish3>]]",
        NULL
};

static int index_output_cb(const struct option *opt, const char *arg,
                                 int unset)
{
        set_alternate_index_output(arg);
        return 0;
}

static int exclude_per_directory_cb(const struct option *opt, const char *arg,
                                    int unset)
{
        struct dir_struct *dir;
        struct unpack_trees_options *opts;

        opts = (struct unpack_trees_options *)opt->value;

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

        dir = xcalloc(1, sizeof(*opts->dir));
        dir->flags |= DIR_SHOW_IGNORED;
        dir->exclude_per_dir = arg;
        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.
         */
        return 0;
}

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;
        int prefix_set = 0;
        const struct option read_tree_options[] = {
                { OPTION_CALLBACK, 0, "index-output", NULL, "FILE",
                  "write resulting index to <FILE>",
                  PARSE_OPT_NONEG, index_output_cb },
                OPT__VERBOSE(&opts.verbose_update),
                OPT_GROUP("Merging"),
                OPT_SET_INT('m', NULL, &opts.merge,
                            "perform a merge in addition to a read", 1),
                OPT_SET_INT(0, "trivial", &opts.trivial_merges_only,
                            "3-way merge if no file level merging required", 1),
                OPT_SET_INT(0, "aggressive", &opts.aggressive,
                            "3-way merge in presence of adds and removes", 1),
                OPT_SET_INT(0, "reset", &opts.reset,
                            "same as -m, but discard unmerged entries", 1),
                { OPTION_STRING, 0, "prefix", &opts.prefix, "<subdirectory>/",
                  "read the tree into the index under <subdirectory>/",
                  PARSE_OPT_NONEG | PARSE_OPT_LITERAL_ARGHELP },
                OPT_SET_INT('u', NULL, &opts.update,
                            "update working tree with merge result", 1),
                { OPTION_CALLBACK, 0, "exclude-per-directory", &opts,
                  "gitignore",
                  "allow explicitly ignored files to be overwritten",
                  PARSE_OPT_NONEG, exclude_per_directory_cb },
                OPT_SET_INT('i', NULL, &opts.index_only,
                            "don't check the working tree after merging", 1),
                OPT_END()
        };

        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);

        argc = parse_options(argc, argv, unused_prefix, read_tree_options,
                             read_tree_usage, 0);

        newfd = hold_locked_index(&lock_file, 1);

        prefix_set = opts.prefix ? 1 : 0;
        if (1 < opts.merge + opts.reset + prefix_set)
                die("Which one? -m, --reset, or --prefix?");

        if (opts.reset || opts.merge || opts.prefix) {
                if (read_cache_unmerged() && (opts.prefix || opts.merge))
                        die("You need to resolve your current index first");
                stage = opts.merge = 1;
        }
        resolve_undo_clear();

        for (i = 0; i < argc; i++) {
                const char *arg = argv[i];

                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 (1 < opts.index_only + opts.update)
                die("-u and -i at the same time makes no sense");
        if ((opts.update||opts.index_only) && !opts.merge)
                die("%s is meaningless without -m, --reset, or --prefix",
                    opts.update ? "-u" : "-i");
        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;
}