#include "cache.h"
#include "diff.h"
#include "commit.h"

static int show_root_diff = 0;
static int verbose_header = 0;
static int ignore_merges = 1;
static int read_stdin = 0;

static const char *header = NULL;
static const char *header_prefix = "";
static enum cmit_fmt commit_format = CMIT_FMT_RAW;

static struct diff_options diff_options;

static void call_diff_setup_done(void)
{
        diff_setup_done(&diff_options);
}

static int call_diff_flush(void)
{
        diffcore_std(&diff_options);
        if (diff_queue_is_empty()) {
                int saved_fmt = diff_options.output_format;
                diff_options.output_format = DIFF_FORMAT_NO_OUTPUT;
                diff_flush(&diff_options);
                diff_options.output_format = saved_fmt;
                return 0;
        }
        if (header) {
                printf("%s%c", header, diff_options.line_termination);
                header = NULL;
        }
        diff_flush(&diff_options);
        return 1;
}

static int diff_tree_sha1_top(const unsigned char *old,
                              const unsigned char *new, const char *base)
{
        int ret;

        call_diff_setup_done();
        ret = diff_tree_sha1(old, new, base, &diff_options);
        call_diff_flush();
        return ret;
}

static int diff_root_tree(const unsigned char *new, const char *base)
{
        int retval;
        void *tree;
        struct tree_desc empty, real;

        call_diff_setup_done();
        tree = read_object_with_reference(new, "tree", &real.size, NULL);
        if (!tree)
                die("unable to read root tree (%s)", sha1_to_hex(new));
        real.buf = tree;

        empty.buf = "";
        empty.size = 0;
        retval = diff_tree(&empty, &real, base, &diff_options);
        free(tree);
        call_diff_flush();
        return retval;
}

static const char *generate_header(const char *commit, const char *parent, const char *msg, unsigned long len)
{
        static char this_header[16384];
        int offset;

        if (!verbose_header)
                return commit;

        offset = sprintf(this_header, "%s%s (from %s)\n", header_prefix, commit, parent);
        offset += pretty_print_commit(commit_format, msg, len, this_header + offset, sizeof(this_header) - offset);
        return this_header;
}

static int diff_tree_commit(const unsigned char *commit, const char *name)
{
        unsigned long size, offset;
        char *buf = read_object_with_reference(commit, "commit", &size, NULL);

        if (!buf)
                return -1;

        if (!name) {
                static char commit_name[60];
                strcpy(commit_name, sha1_to_hex(commit));
                name = commit_name;
        }

        /* Root commit? */
        if (show_root_diff && memcmp(buf + 46, "parent ", 7)) {
                header = generate_header(name, "root", buf, size);
                diff_root_tree(commit, "");
        }

        /* More than one parent? */
        if (ignore_merges) {
                if (!memcmp(buf + 46 + 48, "parent ", 7))
                        return 0;
        }

        offset = 46;
        while (offset + 48 < size && !memcmp(buf + offset, "parent ", 7)) {
                unsigned char parent[20];
                if (get_sha1_hex(buf + offset + 7, parent))
                        return -1;
                header = generate_header(name, sha1_to_hex(parent), buf, size);
                diff_tree_sha1_top(parent, commit, "");
                if (!header && verbose_header) {
                        header_prefix = "\ndiff-tree ";
                        /*
                         * Don't print multiple merge entries if we
                         * don't print the diffs.
                         */
                }
                offset += 48;
        }
        free(buf);
        return 0;
}

static int diff_tree_stdin(char *line)
{
        int len = strlen(line);
        unsigned char commit[20], parent[20];
        static char this_header[1000];

        if (!len || line[len-1] != '\n')
                return -1;
        line[len-1] = 0;
        if (get_sha1_hex(line, commit))
                return -1;
        if (isspace(line[40]) && !get_sha1_hex(line+41, parent)) {
                line[40] = 0;
                line[81] = 0;
                sprintf(this_header, "%s (from %s)\n", line, line+41);
                header = this_header;
                return diff_tree_sha1_top(parent, commit, "");
        }
        line[40] = 0;
        return diff_tree_commit(commit, line);
}

static const char diff_tree_usage[] =
"git-diff-tree [--stdin] [-m] [-s] [-v] [--pretty] [-t] [-r] [--root] "
"[<common diff options>] <tree-ish> [<tree-ish>] [<path>...]\n"
"  -r            diff recursively\n"
"  --root        include the initial commit as diff against /dev/null\n"
COMMON_DIFF_OPTIONS_HELP;

int main(int argc, const char **argv)
{
        int nr_sha1;
        char line[1000];
        unsigned char sha1[2][20];
        const char *prefix = setup_git_directory();

        git_config(git_default_config);
        nr_sha1 = 0;
        diff_setup(&diff_options);

        for (;;) {
                int diff_opt_cnt;
                const char *arg;

                argv++;
                argc--;
                arg = *argv;
                if (!arg)
                        break;

                if (*arg != '-') {
                        if (nr_sha1 < 2 && !get_sha1(arg, sha1[nr_sha1])) {
                                nr_sha1++;
                                continue;
                        }
                        break;
                }

                diff_opt_cnt = diff_opt_parse(&diff_options, argv, argc);
                if (diff_opt_cnt < 0)
                        usage(diff_tree_usage);
                else if (diff_opt_cnt) {
                        argv += diff_opt_cnt - 1;
                        argc -= diff_opt_cnt - 1;
                        continue;
                }


                if (!strcmp(arg, "--")) {
                        argv++;
                        argc--;
                        break;
                }
                if (!strcmp(arg, "-r")) {
                        diff_options.recursive = 1;
                        continue;
                }
                if (!strcmp(arg, "-t")) {
                        diff_options.recursive = 1;
                        diff_options.tree_in_recursive = 1;
                        continue;
                }
                if (!strcmp(arg, "-m")) {
                        ignore_merges = 0;
                        continue;
                }
                if (!strcmp(arg, "-v")) {
                        verbose_header = 1;
                        header_prefix = "diff-tree ";
                        continue;
                }
                if (!strncmp(arg, "--pretty", 8)) {
                        verbose_header = 1;
                        header_prefix = "diff-tree ";
                        commit_format = get_commit_format(arg+8);
                        continue;
                }
                if (!strcmp(arg, "--stdin")) {
                        read_stdin = 1;
                        continue;
                }
                if (!strcmp(arg, "--root")) {
                        show_root_diff = 1;
                        continue;
                }
                usage(diff_tree_usage);
        }
        if (diff_options.output_format == DIFF_FORMAT_PATCH)
                diff_options.recursive = 1;

        diff_tree_setup_paths(get_pathspec(prefix, argv));

        switch (nr_sha1) {
        case 0:
                if (!read_stdin)
                        usage(diff_tree_usage);
                break;
        case 1:
                diff_tree_commit(sha1[0], NULL);
                break;
        case 2:
                diff_tree_sha1_top(sha1[0], sha1[1], "");
                break;
        }

        if (!read_stdin)
                return 0;

        if (diff_options.detect_rename)
                diff_options.setup |= (DIFF_SETUP_USE_SIZE_CACHE |
                                       DIFF_SETUP_USE_CACHE);
        while (fgets(line, sizeof(line), stdin))
                diff_tree_stdin(line);

        return 0;
}