#include "cache.h"
#include "xdiff-interface.h"
#include "strbuf.h"

struct xdiff_emit_state {
        xdiff_emit_consume_fn consume;
        void *consume_callback_data;
        struct strbuf remainder;
};

static int parse_num(char **cp_p, int *num_p)
{
        char *cp = *cp_p;
        int num = 0;
        int read_some;

        while ('0' <= *cp && *cp <= '9')
                num = num * 10 + *cp++ - '0';
        if (!(read_some = cp - *cp_p))
                return -1;
        *cp_p = cp;
        *num_p = num;
        return 0;
}

int parse_hunk_header(char *line, int len,
                      int *ob, int *on,
                      int *nb, int *nn)
{
        char *cp;
        cp = line + 4;
        if (parse_num(&cp, ob)) {
        bad_line:
                return error("malformed diff output: %s", line);
        }
        if (*cp == ',') {
                cp++;
                if (parse_num(&cp, on))
                        goto bad_line;
        }
        else
                *on = 1;
        if (*cp++ != ' ' || *cp++ != '+')
                goto bad_line;
        if (parse_num(&cp, nb))
                goto bad_line;
        if (*cp == ',') {
                cp++;
                if (parse_num(&cp, nn))
                        goto bad_line;
        }
        else
                *nn = 1;
        return -!!memcmp(cp, " @@", 3);
}

static void consume_one(void *priv_, char *s, unsigned long size)
{
        struct xdiff_emit_state *priv = priv_;
        char *ep;
        while (size) {
                unsigned long this_size;
                ep = memchr(s, '\n', size);
                this_size = (ep == NULL) ? size : (ep - s + 1);
                priv->consume(priv->consume_callback_data, s, this_size);
                size -= this_size;
                s += this_size;
        }
}

static int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf)
{
        struct xdiff_emit_state *priv = priv_;
        int i;

        for (i = 0; i < nbuf; i++) {
                if (mb[i].ptr[mb[i].size-1] != '\n') {
                        /* Incomplete line */
                        strbuf_add(&priv->remainder, mb[i].ptr, mb[i].size);
                        continue;
                }

                /* we have a complete line */
                if (!priv->remainder.len) {
                        consume_one(priv, mb[i].ptr, mb[i].size);
                        continue;
                }
                strbuf_add(&priv->remainder, mb[i].ptr, mb[i].size);
                consume_one(priv, priv->remainder.buf, priv->remainder.len);
                strbuf_reset(&priv->remainder);
        }
        if (priv->remainder.len) {
                consume_one(priv, priv->remainder.buf, priv->remainder.len);
                strbuf_reset(&priv->remainder);
        }
        return 0;
}

/*
 * Trim down common substring at the end of the buffers,
 * but leave at least ctx lines at the end.
 */
static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx)
{
        const int blk = 1024;
        long trimmed = 0, recovered = 0;
        char *ap = a->ptr + a->size;
        char *bp = b->ptr + b->size;
        long smaller = (a->size < b->size) ? a->size : b->size;

        if (ctx)
                return;

        while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) {
                trimmed += blk;
                ap -= blk;
                bp -= blk;
        }

        while (recovered < trimmed)
                if (ap[recovered++] == '\n')
                        break;
        a->size -= trimmed - recovered;
        b->size -= trimmed - recovered;
}

int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *xecb)
{
        mmfile_t a = *mf1;
        mmfile_t b = *mf2;

        trim_common_tail(&a, &b, xecfg->ctxlen);

        return xdl_diff(&a, &b, xpp, xecfg, xecb);
}

int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
                  xdiff_emit_consume_fn fn, void *consume_callback_data,
                  xpparam_t const *xpp,
                  xdemitconf_t const *xecfg, xdemitcb_t *xecb)
{
        int ret;
        struct xdiff_emit_state state;

        memset(&state, 0, sizeof(state));
        state.consume = fn;
        state.consume_callback_data = consume_callback_data;
        xecb->outf = xdiff_outf;
        xecb->priv = &state;
        strbuf_init(&state.remainder, 0);
        ret = xdi_diff(mf1, mf2, xpp, xecfg, xecb);
        strbuf_release(&state.remainder);
        return ret;
}

int read_mmfile(mmfile_t *ptr, const char *filename)
{
        struct stat st;
        FILE *f;
        size_t sz;

        if (stat(filename, &st))
                return error("Could not stat %s", filename);
        if ((f = fopen(filename, "rb")) == NULL)
                return error("Could not open %s", filename);
        sz = xsize_t(st.st_size);
        ptr->ptr = xmalloc(sz ? sz : 1);
        if (sz && fread(ptr->ptr, sz, 1, f) != 1)
                return error("Could not read %s", filename);
        fclose(f);
        ptr->size = sz;
        return 0;
}

#define FIRST_FEW_BYTES 8000
int buffer_is_binary(const char *ptr, unsigned long size)
{
        if (FIRST_FEW_BYTES < size)
                size = FIRST_FEW_BYTES;
        return !!memchr(ptr, 0, size);
}

struct ff_regs {
        int nr;
        struct ff_reg {
                regex_t re;
                int negate;
        } *array;
};

static long ff_regexp(const char *line, long len,
                char *buffer, long buffer_size, void *priv)
{
        char *line_buffer = xstrndup(line, len); /* make NUL terminated */
        struct ff_regs *regs = priv;
        regmatch_t pmatch[2];
        int result = 0, i;

        for (i = 0; i < regs->nr; i++) {
                struct ff_reg *reg = regs->array + i;
                if (reg->negate ^ !!regexec(&reg->re,
                                        line_buffer, 2, pmatch, 0)) {
                        free(line_buffer);
                        return -1;
                }
        }
        i = pmatch[1].rm_so >= 0 ? 1 : 0;
        line += pmatch[i].rm_so;
        result = pmatch[i].rm_eo - pmatch[i].rm_so;
        if (result > buffer_size)
                result = buffer_size;
        else
                while (result > 0 && (isspace(line[result - 1]) ||
                                        line[result - 1] == '\n'))
                        result--;
        memcpy(buffer, line, result);
        free(line_buffer);
        return result;
}

void xdiff_set_find_func(xdemitconf_t *xecfg, const char *value)
{
        int i;
        struct ff_regs *regs;

        xecfg->find_func = ff_regexp;
        regs = xecfg->find_func_priv = xmalloc(sizeof(struct ff_regs));
        for (i = 0, regs->nr = 1; value[i]; i++)
                if (value[i] == '\n')
                        regs->nr++;
        regs->array = xmalloc(regs->nr * sizeof(struct ff_reg));
        for (i = 0; i < regs->nr; i++) {
                struct ff_reg *reg = regs->array + i;
                const char *ep = strchr(value, '\n'), *expression;
                char *buffer = NULL;

                reg->negate = (*value == '!');
                if (reg->negate && i == regs->nr - 1)
                        die("Last expression must not be negated: %s", value);
                if (*value == '!')
                        value++;
                if (ep)
                        expression = buffer = xstrndup(value, ep - value);
                else
                        expression = value;
                if (regcomp(&reg->re, expression, 0))
                        die("Invalid regexp to look for hunk header: %s", expression);
                free(buffer);
                value = ep + 1;
        }
}