#include "cache.h"
#include "attr.h"
#include "run-command.h"

/*
 * convert.c - convert a file when checking it out and checking it in.
 *
 * This should use the pathname to decide on whether it wants to do some
 * more interesting conversions (automatic gzip/unzip, general format
 * conversions etc etc), but by default it just does automatic CRLF<->LF
 * translation when the "auto_crlf" option is set.
 */

#define CRLF_GUESS      (-1)
#define CRLF_BINARY     0
#define CRLF_TEXT       1
#define CRLF_INPUT      2

struct text_stat {
        /* NUL, CR, LF and CRLF counts */
        unsigned nul, cr, lf, crlf;

        /* These are just approximations! */
        unsigned printable, nonprintable;
};

static void gather_stats(const char *buf, unsigned long size, struct text_stat *stats)
{
        unsigned long i;

        memset(stats, 0, sizeof(*stats));

        for (i = 0; i < size; i++) {
                unsigned char c = buf[i];
                if (c == '\r') {
                        stats->cr++;
                        if (i+1 < size && buf[i+1] == '\n')
                                stats->crlf++;
                        continue;
                }
                if (c == '\n') {
                        stats->lf++;
                        continue;
                }
                if (c == 127)
                        /* DEL */
                        stats->nonprintable++;
                else if (c < 32) {
                        switch (c) {
                                /* BS, HT, ESC and FF */
                        case '\b': case '\t': case '\033': case '\014':
                                stats->printable++;
                                break;
                        case 0:
                                stats->nul++;
                                /* fall through */
                        default:
                                stats->nonprintable++;
                        }
                }
                else
                        stats->printable++;
        }

        /* If file ends with EOF then don't count this EOF as non-printable. */
        if (size >= 1 && buf[size-1] == '\032')
                stats->nonprintable--;
}

/*
 * The same heuristics as diff.c::mmfile_is_binary()
 */
static int is_binary(unsigned long size, struct text_stat *stats)
{

        if (stats->nul)
                return 1;
        if ((stats->printable >> 7) < stats->nonprintable)
                return 1;
        /*
         * Other heuristics? Average line length might be relevant,
         * as might LF vs CR vs CRLF counts..
         *
         * NOTE! It might be normal to have a low ratio of CRLF to LF
         * (somebody starts with a LF-only file and edits it with an editor
         * that adds CRLF only to lines that are added..). But do  we
         * want to support CR-only? Probably not.
         */
        return 0;
}

static void check_safe_crlf(const char *path, int action,
                            struct text_stat *stats, enum safe_crlf checksafe)
{
        if (!checksafe)
                return;

        if (action == CRLF_INPUT || auto_crlf <= 0) {
                /*
                 * CRLFs would not be restored by checkout:
                 * check if we'd remove CRLFs
                 */
                if (stats->crlf) {
                        if (checksafe == SAFE_CRLF_WARN)
                                warning("CRLF will be replaced by LF in %s.", path);
                        else /* i.e. SAFE_CRLF_FAIL */
                                die("CRLF would be replaced by LF in %s.", path);
                }
        } else if (auto_crlf > 0) {
                /*
                 * CRLFs would be added by checkout:
                 * check if we have "naked" LFs
                 */
                if (stats->lf != stats->crlf) {
                        if (checksafe == SAFE_CRLF_WARN)
                                warning("LF will be replaced by CRLF in %s", path);
                        else /* i.e. SAFE_CRLF_FAIL */
                                die("LF would be replaced by CRLF in %s", path);
                }
        }
}

static int crlf_to_git(const char *path, const char *src, size_t len,
                       struct strbuf *buf, int action, enum safe_crlf checksafe)
{
        struct text_stat stats;
        char *dst;

        if ((action == CRLF_BINARY) || !auto_crlf || !len)
                return 0;

        gather_stats(src, len, &stats);

        if (action == CRLF_GUESS) {
                /*
                 * We're currently not going to even try to convert stuff
                 * that has bare CR characters. Does anybody do that crazy
                 * stuff?
                 */
                if (stats.cr != stats.crlf)
                        return 0;

                /*
                 * And add some heuristics for binary vs text, of course...
                 */
                if (is_binary(len, &stats))
                        return 0;
        }

        check_safe_crlf(path, action, &stats, checksafe);

        /* Optimization: No CR? Nothing to convert, regardless. */
        if (!stats.cr)
                return 0;

        /* only grow if not in place */
        if (strbuf_avail(buf) + buf->len < len)
                strbuf_grow(buf, len - buf->len);
        dst = buf->buf;
        if (action == CRLF_GUESS) {
                /*
                 * If we guessed, we already know we rejected a file with
                 * lone CR, and we can strip a CR without looking at what
                 * follow it.
                 */
                do {
                        unsigned char c = *src++;
                        if (c != '\r')
                                *dst++ = c;
                } while (--len);
        } else {
                do {
                        unsigned char c = *src++;
                        if (! (c == '\r' && (1 < len && *src == '\n')))
                                *dst++ = c;
                } while (--len);
        }
        strbuf_setlen(buf, dst - buf->buf);
        return 1;
}

static int crlf_to_worktree(const char *path, const char *src, size_t len,
                            struct strbuf *buf, int action)
{
        char *to_free = NULL;
        struct text_stat stats;

        if ((action == CRLF_BINARY) || (action == CRLF_INPUT) ||
            auto_crlf <= 0)
                return 0;

        if (!len)
                return 0;

        gather_stats(src, len, &stats);

        /* No LF? Nothing to convert, regardless. */
        if (!stats.lf)
                return 0;

        /* Was it already in CRLF format? */
        if (stats.lf == stats.crlf)
                return 0;

        if (action == CRLF_GUESS) {
                /* If we have any bare CR characters, we're not going to touch it */
                if (stats.cr != stats.crlf)
                        return 0;

                if (is_binary(len, &stats))
                        return 0;
        }

        /* are we "faking" in place editing ? */
        if (src == buf->buf)
                to_free = strbuf_detach(buf, NULL);

        strbuf_grow(buf, len + stats.lf - stats.crlf);
        for (;;) {
                const char *nl = memchr(src, '\n', len);
                if (!nl)
                        break;
                if (nl > src && nl[-1] == '\r') {
                        strbuf_add(buf, src, nl + 1 - src);
                } else {
                        strbuf_add(buf, src, nl - src);
                        strbuf_addstr(buf, "\r\n");
                }
                len -= nl + 1 - src;
                src  = nl + 1;
        }
        strbuf_add(buf, src, len);

        free(to_free);
        return 1;
}

struct filter_params {
        const char *src;
        unsigned long size;
        const char *cmd;
};

static int filter_buffer(int fd, void *data)
{
        /*
         * Spawn cmd and feed the buffer contents through its stdin.
         */
        struct child_process child_process;
        struct filter_params *params = (struct filter_params *)data;
        int write_err, status;
        const char *argv[] = { "sh", "-c", params->cmd, NULL };

        memset(&child_process, 0, sizeof(child_process));
        child_process.argv = argv;
        child_process.in = -1;
        child_process.out = fd;

        if (start_command(&child_process))
                return error("cannot fork to run external filter %s", params->cmd);

        write_err = (write_in_full(child_process.in, params->src, params->size) < 0);
        if (close(child_process.in))
                write_err = 1;
        if (write_err)
                error("cannot feed the input to external filter %s", params->cmd);

        status = finish_command(&child_process);
        if (status)
                error("external filter %s failed %d", params->cmd, -status);
        return (write_err || status);
}

static int apply_filter(const char *path, const char *src, size_t len,
                        struct strbuf *dst, const char *cmd)
{
        /*
         * Create a pipeline to have the command filter the buffer's
         * contents.
         *
         * (child --> cmd) --> us
         */
        int ret = 1;
        struct strbuf nbuf;
        struct async async;
        struct filter_params params;

        if (!cmd)
                return 0;

        memset(&async, 0, sizeof(async));
        async.proc = filter_buffer;
        async.data = &params;
        params.src = src;
        params.size = len;
        params.cmd = cmd;

        fflush(NULL);
        if (start_async(&async))
                return 0;       /* error was already reported */

        strbuf_init(&nbuf, 0);
        if (strbuf_read(&nbuf, async.out, len) < 0) {
                error("read from external filter %s failed", cmd);
                ret = 0;
        }
        if (close(async.out)) {
                error("read from external filter %s failed", cmd);
                ret = 0;
        }
        if (finish_async(&async)) {
                error("external filter %s failed", cmd);
                ret = 0;
        }

        if (ret) {
                strbuf_swap(dst, &nbuf);
        }
        strbuf_release(&nbuf);
        return ret;
}

static struct convert_driver {
        const char *name;
        struct convert_driver *next;
        const char *smudge;
        const char *clean;
} *user_convert, **user_convert_tail;

static int read_convert_config(const char *var, const char *value, void *cb)
{
        const char *ep, *name;
        int namelen;
        struct convert_driver *drv;

        /*
         * External conversion drivers are configured using
         * "filter.<name>.variable".
         */
        if (prefixcmp(var, "filter.") || (ep = strrchr(var, '.')) == var + 6)
                return 0;
        name = var + 7;
        namelen = ep - name;
        for (drv = user_convert; drv; drv = drv->next)
                if (!strncmp(drv->name, name, namelen) && !drv->name[namelen])
                        break;
        if (!drv) {
                drv = xcalloc(1, sizeof(struct convert_driver));
                drv->name = xmemdupz(name, namelen);
                *user_convert_tail = drv;
                user_convert_tail = &(drv->next);
        }

        ep++;

        /*
         * filter.<name>.smudge and filter.<name>.clean specifies
         * the command line:
         *
         *      command-line
         *
         * The command-line will not be interpolated in any way.
         */

        if (!strcmp("smudge", ep))
                return git_config_string(&drv->smudge, var, value);

        if (!strcmp("clean", ep))
                return git_config_string(&drv->clean, var, value);

        return 0;
}

static void setup_convert_check(struct git_attr_check *check)
{
        static struct git_attr *attr_crlf;
        static struct git_attr *attr_ident;
        static struct git_attr *attr_filter;

        if (!attr_crlf) {
                attr_crlf = git_attr("crlf", 4);
                attr_ident = git_attr("ident", 5);
                attr_filter = git_attr("filter", 6);
                user_convert_tail = &user_convert;
                git_config(read_convert_config, NULL);
        }
        check[0].attr = attr_crlf;
        check[1].attr = attr_ident;
        check[2].attr = attr_filter;
}

static int count_ident(const char *cp, unsigned long size)
{
        /*
         * "$Id: 0000000000000000000000000000000000000000 $" <=> "$Id$"
         */
        int cnt = 0;
        char ch;

        while (size) {
                ch = *cp++;
                size--;
                if (ch != '$')
                        continue;
                if (size < 3)
                        break;
                if (memcmp("Id", cp, 2))
                        continue;
                ch = cp[2];
                cp += 3;
                size -= 3;
                if (ch == '$')
                        cnt++; /* $Id$ */
                if (ch != ':')
                        continue;

                /*
                 * "$Id: ... "; scan up to the closing dollar sign and discard.
                 */
                while (size) {
                        ch = *cp++;
                        size--;
                        if (ch == '$') {
                                cnt++;
                                break;
                        }
                }
        }
        return cnt;
}

static int ident_to_git(const char *path, const char *src, size_t len,
                        struct strbuf *buf, int ident)
{
        char *dst, *dollar;

        if (!ident || !count_ident(src, len))
                return 0;

        /* only grow if not in place */
        if (strbuf_avail(buf) + buf->len < len)
                strbuf_grow(buf, len - buf->len);
        dst = buf->buf;
        for (;;) {
                dollar = memchr(src, '$', len);
                if (!dollar)
                        break;
                memcpy(dst, src, dollar + 1 - src);
                dst += dollar + 1 - src;
                len -= dollar + 1 - src;
                src  = dollar + 1;

                if (len > 3 && !memcmp(src, "Id:", 3)) {
                        dollar = memchr(src + 3, '$', len - 3);
                        if (!dollar)
                                break;
                        memcpy(dst, "Id$", 3);
                        dst += 3;
                        len -= dollar + 1 - src;
                        src  = dollar + 1;
                }
        }
        memcpy(dst, src, len);
        strbuf_setlen(buf, dst + len - buf->buf);
        return 1;
}

static int ident_to_worktree(const char *path, const char *src, size_t len,
                             struct strbuf *buf, int ident)
{
        unsigned char sha1[20];
        char *to_free = NULL, *dollar;
        int cnt;

        if (!ident)
                return 0;

        cnt = count_ident(src, len);
        if (!cnt)
                return 0;

        /* are we "faking" in place editing ? */
        if (src == buf->buf)
                to_free = strbuf_detach(buf, NULL);
        hash_sha1_file(src, len, "blob", sha1);

        strbuf_grow(buf, len + cnt * 43);
        for (;;) {
                /* step 1: run to the next '$' */
                dollar = memchr(src, '$', len);
                if (!dollar)
                        break;
                strbuf_add(buf, src, dollar + 1 - src);
                len -= dollar + 1 - src;
                src  = dollar + 1;

                /* step 2: does it looks like a bit like Id:xxx$ or Id$ ? */
                if (len < 3 || memcmp("Id", src, 2))
                        continue;

                /* step 3: skip over Id$ or Id:xxxxx$ */
                if (src[2] == '$') {
                        src += 3;
                        len -= 3;
                } else if (src[2] == ':') {
                        /*
                         * It's possible that an expanded Id has crept its way into the
                         * repository, we cope with that by stripping the expansion out
                         */
                        dollar = memchr(src + 3, '$', len - 3);
                        if (!dollar) {
                                /* incomplete keyword, no more '$', so just quit the loop */
                                break;
                        }

                        len -= dollar + 1 - src;
                        src  = dollar + 1;
                } else {
                        /* it wasn't a "Id$" or "Id:xxxx$" */
                        continue;
                }

                /* step 4: substitute */
                strbuf_addstr(buf, "Id: ");
                strbuf_add(buf, sha1_to_hex(sha1), 40);
                strbuf_addstr(buf, " $");
        }
        strbuf_add(buf, src, len);

        free(to_free);
        return 1;
}

static int git_path_check_crlf(const char *path, struct git_attr_check *check)
{
        const char *value = check->value;

        if (ATTR_TRUE(value))
                return CRLF_TEXT;
        else if (ATTR_FALSE(value))
                return CRLF_BINARY;
        else if (ATTR_UNSET(value))
                ;
        else if (!strcmp(value, "input"))
                return CRLF_INPUT;
        return CRLF_GUESS;
}

static struct convert_driver *git_path_check_convert(const char *path,
                                             struct git_attr_check *check)
{
        const char *value = check->value;
        struct convert_driver *drv;

        if (ATTR_TRUE(value) || ATTR_FALSE(value) || ATTR_UNSET(value))
                return NULL;
        for (drv = user_convert; drv; drv = drv->next)
                if (!strcmp(value, drv->name))
                        return drv;
        return NULL;
}

static int git_path_check_ident(const char *path, struct git_attr_check *check)
{
        const char *value = check->value;

        return !!ATTR_TRUE(value);
}

int convert_to_git(const char *path, const char *src, size_t len,
                   struct strbuf *dst, enum safe_crlf checksafe)
{
        struct git_attr_check check[3];
        int crlf = CRLF_GUESS;
        int ident = 0, ret = 0;
        const char *filter = NULL;

        setup_convert_check(check);
        if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
                struct convert_driver *drv;
                crlf = git_path_check_crlf(path, check + 0);
                ident = git_path_check_ident(path, check + 1);
                drv = git_path_check_convert(path, check + 2);
                if (drv && drv->clean)
                        filter = drv->clean;
        }

        ret |= apply_filter(path, src, len, dst, filter);
        if (ret) {
                src = dst->buf;
                len = dst->len;
        }
        ret |= crlf_to_git(path, src, len, dst, crlf, checksafe);
        if (ret) {
                src = dst->buf;
                len = dst->len;
        }
        return ret | ident_to_git(path, src, len, dst, ident);
}

int convert_to_working_tree(const char *path, const char *src, size_t len, struct strbuf *dst)
{
        struct git_attr_check check[3];
        int crlf = CRLF_GUESS;
        int ident = 0, ret = 0;
        const char *filter = NULL;

        setup_convert_check(check);
        if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
                struct convert_driver *drv;
                crlf = git_path_check_crlf(path, check + 0);
                ident = git_path_check_ident(path, check + 1);
                drv = git_path_check_convert(path, check + 2);
                if (drv && drv->smudge)
                        filter = drv->smudge;
        }

        ret |= ident_to_worktree(path, src, len, dst, ident);
        if (ret) {
                src = dst->buf;
                len = dst->len;
        }
        ret |= crlf_to_worktree(path, src, len, dst, crlf);
        if (ret) {
                src = dst->buf;
                len = dst->len;
        }
        return ret | apply_filter(path, src, len, dst, filter);
}