#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 recursive = 0;
static int show_tree_entry_in_recursive = 0;
static int read_stdin = 0;

static struct diff_options diff_options;

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

// What paths are we interested in?
static int nr_paths = 0;
static const char **paths = NULL;
static int *pathlens = NULL;

static int diff_tree_sha1(const unsigned char *old, const unsigned char *new, const char *base);

static void update_tree_entry(void **bufp, unsigned long *sizep)
{
        void *buf = *bufp;
        unsigned long size = *sizep;
        int len = strlen(buf) + 1 + 20;

        if (size < len)
                die("corrupt tree file");
        *bufp = buf + len;
        *sizep = size - len;
}

static const unsigned char *extract(void *tree, unsigned long size, const char **pathp, unsigned int *modep)
{
        int len = strlen(tree)+1;
        const unsigned char *sha1 = tree + len;
        const char *path = strchr(tree, ' ');
        unsigned int mode;

        if (!path || size < len + 20 || sscanf(tree, "%o", &mode) != 1)
                die("corrupt tree file");
        *pathp = path+1;
        *modep = DIFF_FILE_CANON_MODE(mode);
        return sha1;
}

static char *malloc_base(const char *base, const char *path, int pathlen)
{
        int baselen = strlen(base);
        char *newbase = xmalloc(baselen + pathlen + 2);
        memcpy(newbase, base, baselen);
        memcpy(newbase + baselen, path, pathlen);
        memcpy(newbase + baselen + pathlen, "/", 2);
        return newbase;
}

static void show_file(const char *prefix, void *tree, unsigned long size, const char *base);
static void show_tree(const char *prefix, void *tree, unsigned long size, const char *base);

/* A file entry went away or appeared */
static void show_file(const char *prefix, void *tree, unsigned long size, const char *base)
{
        unsigned mode;
        const char *path;
        const unsigned char *sha1 = extract(tree, size, &path, &mode);

        if (recursive && S_ISDIR(mode)) {
                char type[20];
                unsigned long size;
                char *newbase = malloc_base(base, path, strlen(path));
                void *tree;

                tree = read_sha1_file(sha1, type, &size);
                if (!tree || strcmp(type, "tree"))
                        die("corrupt tree sha %s", sha1_to_hex(sha1));

                show_tree(prefix, tree, size, newbase);

                free(tree);
                free(newbase);
                return;
        }

        diff_addremove(&diff_options, prefix[0], mode, sha1, base, path);
}

static int compare_tree_entry(void *tree1, unsigned long size1, void *tree2, unsigned long size2, const char *base)
{
        unsigned mode1, mode2;
        const char *path1, *path2;
        const unsigned char *sha1, *sha2;
        int cmp, pathlen1, pathlen2;

        sha1 = extract(tree1, size1, &path1, &mode1);
        sha2 = extract(tree2, size2, &path2, &mode2);

        pathlen1 = strlen(path1);
        pathlen2 = strlen(path2);
        cmp = base_name_compare(path1, pathlen1, mode1, path2, pathlen2, mode2);
        if (cmp < 0) {
                show_file("-", tree1, size1, base);
                return -1;
        }
        if (cmp > 0) {
                show_file("+", tree2, size2, base);
                return 1;
        }
        if (!diff_options.find_copies_harder &&
            !memcmp(sha1, sha2, 20) && mode1 == mode2)
                return 0;

        /*
         * If the filemode has changed to/from a directory from/to a regular
         * file, we need to consider it a remove and an add.
         */
        if (S_ISDIR(mode1) != S_ISDIR(mode2)) {
                show_file("-", tree1, size1, base);
                show_file("+", tree2, size2, base);
                return 0;
        }

        if (recursive && S_ISDIR(mode1)) {
                int retval;
                char *newbase = malloc_base(base, path1, pathlen1);
                if (show_tree_entry_in_recursive)
                        diff_change(&diff_options, mode1, mode2,
                                    sha1, sha2, base, path1);
                retval = diff_tree_sha1(sha1, sha2, newbase);
                free(newbase);
                return retval;
        }

        diff_change(&diff_options, mode1, mode2, sha1, sha2, base, path1);
        return 0;
}

static int interesting(void *tree, unsigned long size, const char *base)
{
        const char *path;
        unsigned mode;
        int i;
        int baselen, pathlen;

        if (!nr_paths)
                return 1;

        (void)extract(tree, size, &path, &mode);

        pathlen = strlen(path);
        baselen = strlen(base);

        for (i=0; i < nr_paths; i++) {
                const char *match = paths[i];
                int matchlen = pathlens[i];

                if (baselen >= matchlen) {
                        /* If it doesn't match, move along... */
                        if (strncmp(base, match, matchlen))
                                continue;

                        /* The base is a subdirectory of a path which was specified. */
                        return 1;
                }

                /* Does the base match? */
                if (strncmp(base, match, baselen))
                        continue;

                match += baselen;
                matchlen -= baselen;

                if (pathlen > matchlen)
                        continue;

                if (matchlen > pathlen) {
                        if (match[pathlen] != '/')
                                continue;
                        if (!S_ISDIR(mode))
                                continue;
                }

                if (strncmp(path, match, pathlen))
                        continue;

                return 1;
        }
        return 0; /* No matches */
}

/* A whole sub-tree went away or appeared */
static void show_tree(const char *prefix, void *tree, unsigned long size, const char *base)
{
        while (size) {
                if (interesting(tree, size, base))
                        show_file(prefix, tree, size, base);
                update_tree_entry(&tree, &size);
        }
}

static int diff_tree(void *tree1, unsigned long size1, void *tree2, unsigned long size2, const char *base)
{
        while (size1 | size2) {
                if (nr_paths && size1 && !interesting(tree1, size1, base)) {
                        update_tree_entry(&tree1, &size1);
                        continue;
                }
                if (nr_paths && size2 && !interesting(tree2, size2, base)) {
                        update_tree_entry(&tree2, &size2);
                        continue;
                }
                if (!size1) {
                        show_file("+", tree2, size2, base);
                        update_tree_entry(&tree2, &size2);
                        continue;
                }
                if (!size2) {
                        show_file("-", tree1, size1, base);
                        update_tree_entry(&tree1, &size1);
                        continue;
                }
                switch (compare_tree_entry(tree1, size1, tree2, size2, base)) {
                case -1:
                        update_tree_entry(&tree1, &size1);
                        continue;
                case 0:
                        update_tree_entry(&tree1, &size1);
                        /* Fallthrough */
                case 1:
                        update_tree_entry(&tree2, &size2);
                        continue;
                }
                die("git-diff-tree: internal error");
        }
        return 0;
}

static int diff_tree_sha1(const unsigned char *old, const unsigned char *new, const char *base)
{
        void *tree1, *tree2;
        unsigned long size1, size2;
        int retval;

        tree1 = read_object_with_reference(old, "tree", &size1, NULL);
        if (!tree1)
                die("unable to read source tree (%s)", sha1_to_hex(old));
        tree2 = read_object_with_reference(new, "tree", &size2, NULL);
        if (!tree2)
                die("unable to read destination tree (%s)", sha1_to_hex(new));
        retval = diff_tree(tree1, size1, tree2, size2, base);
        free(tree1);
        free(tree2);
        return retval;
}

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);
        call_diff_flush();
        return ret;
}

static int diff_root_tree(const unsigned char *new, const char *base)
{
        int retval;
        void *tree;
        unsigned long size;

        call_diff_setup_done();
        tree = read_object_with_reference(new, "tree", &size, NULL);
        if (!tree)
                die("unable to read root tree (%s)", sha1_to_hex(new));
        retval = diff_tree("", 0, tree, size, base);
        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 int count_paths(const char **paths)
{
        int i = 0;
        while (*paths++)
                i++;
        return i;
}

static const char diff_tree_usage[] =
"git-diff-tree [--stdin] [-m] [-s] [-v] [--pretty] [-t] "
"[<common diff options>] <tree-ish> <tree-ish>"
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")) {
                        recursive = 1;
                        continue;
                }
                if (!strcmp(arg, "-t")) {
                        recursive = show_tree_entry_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)
                recursive = 1;

        paths = get_pathspec(prefix, argv);
        if (paths) {
                int i;

                nr_paths = count_paths(paths);
                pathlens = xmalloc(nr_paths * sizeof(int));
                for (i=0; i<nr_paths; i++)
                        pathlens[i] = strlen(paths[i]);
        }

        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;
}