#include "cache.h"
#include "path-list.h"
#include "xdiff/xdiff.h"
#include "xdiff-interface.h"

#include <time.h>

static const char git_rerere_usage[] =
"git-rerere [clear | status | diff | gc]";

/* these values are days */
static int cutoff_noresolve = 15;
static int cutoff_resolve = 60;

static char *merge_rr_path;

static const char *rr_path(const char *name, const char *file)
{
        return git_path("rr-cache/%s/%s", name, file);
}

static void read_rr(struct path_list *rr)
{
        unsigned char sha1[20];
        char buf[PATH_MAX];
        FILE *in = fopen(merge_rr_path, "r");
        if (!in)
                return;
        while (fread(buf, 40, 1, in) == 1) {
                int i;
                char *name;
                if (get_sha1_hex(buf, sha1))
                        die("corrupt MERGE_RR");
                buf[40] = '\0';
                name = xstrdup(buf);
                if (fgetc(in) != '\t')
                        die("corrupt MERGE_RR");
                for (i = 0; i < sizeof(buf) && (buf[i] = fgetc(in)); i++)
                        ; /* do nothing */
                if (i == sizeof(buf))
                        die("filename too long");
                path_list_insert(buf, rr)->util = xstrdup(name);
        }
        fclose(in);
}

static struct lock_file write_lock;

static int write_rr(struct path_list *rr, int out_fd)
{
        int i;
        for (i = 0; i < rr->nr; i++) {
                const char *path = rr->items[i].path;
                write(out_fd, rr->items[i].util, 40);
                write(out_fd, "\t", 1);
                write(out_fd, path, strlen(path) + 1);
        }
        close(out_fd);
        return commit_lock_file(&write_lock);
}

struct buffer {
        char *ptr;
        int nr, alloc;
};

static void append_line(struct buffer *buffer, const char *line)
{
        int len = strlen(line);

        if (buffer->nr + len > buffer->alloc) {
                buffer->alloc = alloc_nr(buffer->nr + len);
                buffer->ptr = xrealloc(buffer->ptr, buffer->alloc);
        }
        memcpy(buffer->ptr + buffer->nr, line, len);
        buffer->nr += len;
}

static int handle_file(const char *path,
         unsigned char *sha1, const char *output)
{
        SHA_CTX ctx;
        char buf[1024];
        int hunk = 0, hunk_no = 0;
        struct buffer minus = { NULL, 0, 0 }, plus = { NULL, 0, 0 };
        struct buffer *one = &minus, *two = &plus;
        FILE *f = fopen(path, "r");
        FILE *out;

        if (!f)
                return error("Could not open %s", path);

        if (output) {
                out = fopen(output, "w");
                if (!out) {
                        fclose(f);
                        return error("Could not write %s", output);
                }
        } else
                out = NULL;

        if (sha1)
                SHA1_Init(&ctx);

        while (fgets(buf, sizeof(buf), f)) {
                if (!strncmp("<<<<<<< ", buf, 8))
                        hunk = 1;
                else if (!strncmp("=======", buf, 7))
                        hunk = 2;
                else if (!strncmp(">>>>>>> ", buf, 8)) {
                        hunk_no++;
                        hunk = 0;
                        if (memcmp(one->ptr, two->ptr, one->nr < two->nr ?
                                                one->nr : two->nr) > 0) {
                                struct buffer *swap = one;
                                one = two;
                                two = swap;
                        }
                        if (out) {
                                fputs("<<<<<<<\n", out);
                                fwrite(one->ptr, one->nr, 1, out);
                                fputs("=======\n", out);
                                fwrite(two->ptr, two->nr, 1, out);
                                fputs(">>>>>>>\n", out);
                        }
                        if (sha1) {
                                SHA1_Update(&ctx, one->ptr, one->nr);
                                SHA1_Update(&ctx, "\0", 1);
                                SHA1_Update(&ctx, two->ptr, two->nr);
                                SHA1_Update(&ctx, "\0", 1);
                        }
                } else if (hunk == 1)
                        append_line(one, buf);
                else if (hunk == 2)
                        append_line(two, buf);
                else if (out)
                        fputs(buf, out);
        }

        fclose(f);
        if (out)
                fclose(out);
        if (sha1)
                SHA1_Final(sha1, &ctx);
        return hunk_no;
}

static int find_conflict(struct path_list *conflict)
{
        int i;
        if (read_cache() < 0)
                return error("Could not read index");
        for (i = 0; i + 2 < active_nr; i++) {
                struct cache_entry *e1 = active_cache[i];
                struct cache_entry *e2 = active_cache[i + 1];
                struct cache_entry *e3 = active_cache[i + 2];
                if (ce_stage(e1) == 1 && ce_stage(e2) == 2 &&
                                ce_stage(e3) == 3 && ce_same_name(e1, e2) &&
                                ce_same_name(e1, e3)) {
                        path_list_insert((const char *)e1->name, conflict);
                        i += 3;
                }
        }
        return 0;
}

static int merge(const char *name, const char *path)
{
        int ret;
        mmfile_t cur, base, other;
        mmbuffer_t result = {NULL, 0};
        xpparam_t xpp = {XDF_NEED_MINIMAL};

        if (handle_file(path, NULL, rr_path(name, "thisimage")) < 0)
                return 1;

        if (read_mmfile(&cur, rr_path(name, "thisimage")) ||
                        read_mmfile(&base, rr_path(name, "preimage")) ||
                        read_mmfile(&other, rr_path(name, "postimage")))
                return 1;
        ret = xdl_merge(&base, &cur, "", &other, "",
                        &xpp, XDL_MERGE_ZEALOUS, &result);
        if (!ret) {
                FILE *f = fopen(path, "w");
                if (!f)
                        return error("Could not write to %s", path);
                fwrite(result.ptr, result.size, 1, f);
                fclose(f);
        }

        free(cur.ptr);
        free(base.ptr);
        free(other.ptr);
        free(result.ptr);

        return ret;
}

static void unlink_rr_item(const char *name)
{
        unlink(rr_path(name, "thisimage"));
        unlink(rr_path(name, "preimage"));
        unlink(rr_path(name, "postimage"));
        rmdir(git_path("rr-cache/%s", name));
}

static void garbage_collect(struct path_list *rr)
{
        struct path_list to_remove = { NULL, 0, 0, 1 };
        char buf[1024];
        DIR *dir;
        struct dirent *e;
        int len, i, cutoff;
        time_t now = time(NULL), then;

        strlcpy(buf, git_path("rr-cache"), sizeof(buf));
        len = strlen(buf);
        dir = opendir(buf);
        strcpy(buf + len++, "/");
        while ((e = readdir(dir))) {
                const char *name = e->d_name;
                struct stat st;
                if (name[0] == '.' && (name[1] == '\0' ||
                                        (name[1] == '.' && name[2] == '\0')))
                        continue;
                i = snprintf(buf + len, sizeof(buf) - len, "%s", name);
                strlcpy(buf + len + i, "/preimage", sizeof(buf) - len - i);
                if (stat(buf, &st))
                        continue;
                then = st.st_mtime;
                strlcpy(buf + len + i, "/postimage", sizeof(buf) - len - i);
                cutoff = stat(buf, &st) ? cutoff_noresolve : cutoff_resolve;
                if (then < now - cutoff * 86400) {
                        buf[len + i] = '\0';
                        path_list_insert(xstrdup(name), &to_remove);
                }
        }
        for (i = 0; i < to_remove.nr; i++)
                unlink_rr_item(to_remove.items[i].path);
        path_list_clear(&to_remove, 0);
}

static int outf(void *dummy, mmbuffer_t *ptr, int nbuf)
{
        int i;
        for (i = 0; i < nbuf; i++)
                write(1, ptr[i].ptr, ptr[i].size);
        return 0;
}

static int diff_two(const char *file1, const char *label1,
                const char *file2, const char *label2)
{
        xpparam_t xpp;
        xdemitconf_t xecfg;
        xdemitcb_t ecb;
        mmfile_t minus, plus;

        if (read_mmfile(&minus, file1) || read_mmfile(&plus, file2))
                return 1;

        printf("--- a/%s\n+++ b/%s\n", label1, label2);
        fflush(stdout);
        xpp.flags = XDF_NEED_MINIMAL;
        xecfg.ctxlen = 3;
        xecfg.flags = 0;
        ecb.outf = outf;
        xdl_diff(&minus, &plus, &xpp, &xecfg, &ecb);

        free(minus.ptr);
        free(plus.ptr);
        return 0;
}

static int copy_file(const char *src, const char *dest)
{
        FILE *in, *out;
        char buffer[32768];
        int count;

        if (!(in = fopen(src, "r")))
                return error("Could not open %s", src);
        if (!(out = fopen(dest, "w")))
                return error("Could not open %s", dest);
        while ((count = fread(buffer, 1, sizeof(buffer), in)))
                fwrite(buffer, 1, count, out);
        fclose(in);
        fclose(out);
        return 0;
}

static int do_plain_rerere(struct path_list *rr, int fd)
{
        struct path_list conflict = { NULL, 0, 0, 1 };
        int i;

        find_conflict(&conflict);

        /*
         * MERGE_RR records paths with conflicts immediately after merge
         * failed.  Some of the conflicted paths might have been hand resolved
         * in the working tree since then, but the initial run would catch all
         * and register their preimages.
         */

        for (i = 0; i < conflict.nr; i++) {
                const char *path = conflict.items[i].path;
                if (!path_list_has_path(rr, path)) {
                        unsigned char sha1[20];
                        char *hex;
                        int ret;
                        ret = handle_file(path, sha1, NULL);
                        if (ret < 1)
                                continue;
                        hex = xstrdup(sha1_to_hex(sha1));
                        path_list_insert(path, rr)->util = hex;
                        if (mkdir(git_path("rr-cache/%s", hex), 0755))
                                continue;;
                        handle_file(path, NULL, rr_path(hex, "preimage"));
                        fprintf(stderr, "Recorded preimage for '%s'\n", path);
                }
        }

        /*
         * Now some of the paths that had conflicts earlier might have been
         * hand resolved.  Others may be similar to a conflict already that
         * was resolved before.
         */

        for (i = 0; i < rr->nr; i++) {
                struct stat st;
                int ret;
                const char *path = rr->items[i].path;
                const char *name = (const char *)rr->items[i].util;

                if (!stat(rr_path(name, "preimage"), &st) &&
                                !stat(rr_path(name, "postimage"), &st)) {
                        if (!merge(name, path)) {
                                fprintf(stderr, "Resolved '%s' using "
                                                "previous resolution.\n", path);
                                goto tail_optimization;
                        }
                }

                /* Let's see if we have resolved it. */
                ret = handle_file(path, NULL, NULL);
                if (ret)
                        continue;

                fprintf(stderr, "Recorded resolution for '%s'.\n", path);
                copy_file(path, rr_path(name, "postimage"));
tail_optimization:
                if (i < rr->nr - 1) {
                        memmove(rr->items + i,
                                        rr->items + i + 1,
                                        rr->nr - i - 1);
                }
                rr->nr--;
                i--;
        }

        return write_rr(rr, fd);
}

static int git_rerere_config(const char *var, const char *value)
{
        if (!strcmp(var, "gc.rerereresolved"))
                cutoff_resolve = git_config_int(var, value);
        else if (!strcmp(var, "gc.rerereunresolved"))
                cutoff_noresolve = git_config_int(var, value);
        else
                return git_default_config(var, value);
        return 0;
}

int cmd_rerere(int argc, const char **argv, const char *prefix)
{
        struct path_list merge_rr = { NULL, 0, 0, 1 };
        int i, fd = -1;
        struct stat st;

        if (stat(git_path("rr-cache"), &st) || !S_ISDIR(st.st_mode))
                return 0;

        git_config(git_rerere_config);

        merge_rr_path = xstrdup(git_path("rr-cache/MERGE_RR"));
        fd = hold_lock_file_for_update(&write_lock, merge_rr_path, 1);
        read_rr(&merge_rr);

        if (argc < 2)
                return do_plain_rerere(&merge_rr, fd);
        else if (!strcmp(argv[1], "clear")) {
                for (i = 0; i < merge_rr.nr; i++) {
                        const char *name = (const char *)merge_rr.items[i].util;
                        if (!stat(git_path("rr-cache/%s", name), &st) &&
                                        S_ISDIR(st.st_mode) &&
                                        stat(rr_path(name, "postimage"), &st))
                                unlink_rr_item(name);
                }
                unlink(merge_rr_path);
        } else if (!strcmp(argv[1], "gc"))
                garbage_collect(&merge_rr);
        else if (!strcmp(argv[1], "status"))
                for (i = 0; i < merge_rr.nr; i++)
                        printf("%s\n", merge_rr.items[i].path);
        else if (!strcmp(argv[1], "diff"))
                for (i = 0; i < merge_rr.nr; i++) {
                        const char *path = merge_rr.items[i].path;
                        const char *name = (const char *)merge_rr.items[i].util;
                        diff_two(rr_path(name, "preimage"), path, path, path);
                }
        else
                usage(git_rerere_usage);

        path_list_clear(&merge_rr, 1);
        return 0;
}