/* radare - LGPL - Copyright 2009-2010 pancake<nopcode.org> */

/* Adapted code from:

 bdiff.c - efficient binary diff extension for Mercurial

 Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>

 This software may be used and distributed according to the terms of

 the GNU General Public License, incorporated herein by reference.

 Based roughly on Python difflib

*/

#include <r_util.h>

#include <r_diff.h>

#include <stdlib.h>

#include <string.h>

#include <limits.h>

struct line {

	int h, len, n, e;

	const char *l;

};

struct pos {

	int pos, len;

};

struct hunk {

	int a1, a2, b1, b2;

};

struct hunklist {

	struct hunk *base, *head;

};

static int splitlines(const char *a, int len, struct line **lr)

{

	int h, i;

	const char *p, *b = a;

	const char * const plast = a + len - 1;

	struct line *l;

	if (a == NULL) {

		eprintf ("null pointer received\n");

		return 0;

	}

	/* count the lines */

	i = 1; /* extra line for sentinel */

	for (p = a; p < a + len; p++)

		if (*p == '\n' || p == plast)

			i++;

	*lr = l = (struct line *)malloc(sizeof(struct line) * i);

	if (!l)

		return -1;

	/* build the line array and calculate hashes */

	h = 0;

	for (p = a; p < a + len; p++) {

		/* Leonid Yuriev's hash */

		h = (h * 1664525) + *p + 1013904223;

		if (*p == '\n' || p == plast) {

			l->h = h;

			h = 0;

			l->len = p - b + 1;

			l->l = b;

			l->n = INT_MAX;

			l++;

			b = p + 1;

		}

	}

	/* set up a sentinel */

	l->h = l->len = 0;

	l->l = a + len;

	return i - 1;

}

static int inline cmp(struct line *a, struct line *b)

{

	return a->h != b->h || a->len != b->len || memcmp(a->l, b->l, a->len);

}

static int equatelines(struct line *a, int an, struct line *b, int bn)

{

	int i, j, buckets = 1, t, scale;

	struct pos *h = NULL;

	/* build a hash table of the next highest power of 2 */

	while (buckets < bn + 1)

		buckets *= 2;

	/* try to allocate a large hash table to avoid collisions */

	for (scale = 4; scale; scale /= 2) {

		h = (struct pos *)malloc(scale * buckets * sizeof(struct pos));

		if (h)

			break;

	}

	if (!h)

		return 0;

	buckets = buckets * scale - 1;

	/* clear the hash table */

	for (i = 0; i <= buckets; i++) {

		h[i].pos = INT_MAX;

		h[i].len = 0;

	}

	/* add lines to the hash table chains */

	for (i = bn - 1; i >= 0; i--) {

		/* find the equivalence class */

		for (j = b[i].h & buckets; h[j].pos != INT_MAX;

		     j = (j + 1) & buckets)

			if (!cmp(b + i, b + h[j].pos))

				break;

		/* add to the head of the equivalence class */

		b[i].n = h[j].pos;

		b[i].e = j;

		h[j].pos = i;

		h[j].len++; /* keep track of popularity */

	}

	/* compute popularity threshold */

	t = (bn >= 4000) ? bn / 1000 : bn + 1;

	/* match items in a to their equivalence class in b */

	for (i = 0; i < an; i++) {

		/* find the equivalence class */

		for (j = a[i].h & buckets; h[j].pos != INT_MAX;

		     j = (j + 1) & buckets)

			if (!cmp(a + i, b + h[j].pos))

				break;

		a[i].e = j; /* use equivalence class for quick compare */

		if (h[j].len <= t)

			a[i].n = h[j].pos; /* point to head of match list */

		else

			a[i].n = INT_MAX; /* too popular */

	}

	/* discard hash tables */

	free(h);

	return 1;

}

static int longest_match(struct line *a, struct line *b, struct pos *pos,

			 int a1, int a2, int b1, int b2, int *omi, int *omj)

{

	int mi = a1, mj = b1, mk = 0, mb = 0, i, j, k;

	for (i = a1; i < a2; i++) {

		/* skip things before the current block */

		for (j = a[i].n; j < b1; j = b[j].n)

			;

		/* loop through all lines match a[i] in b */

		for (; j < b2; j = b[j].n) {

			/* does this extend an earlier match? */

			if (i > a1 && j > b1 && pos[j - 1].pos == i - 1)

				k = pos[j - 1].len + 1;

			else

				k = 1;

			pos[j].pos = i;

			pos[j].len = k;

			/* best match so far? */

			if (k > mk) {

				mi = i;

				mj = j;

				mk = k;

			}

		}

	}

	if (mk) {

		mi = mi - mk + 1;

		mj = mj - mk + 1;

	}

	/* expand match to include neighboring popular lines */

	while (mi - mb > a1 && mj - mb > b1 &&

	       a[mi - mb - 1].e == b[mj - mb - 1].e)

		mb++;

	while (mi + mk < a2 && mj + mk < b2 &&

	       a[mi + mk].e == b[mj + mk].e)

		mk++;

	*omi = mi - mb;

	*omj = mj - mb;

	return mk + mb;

}

static void recurse(struct line *a, struct line *b, struct pos *pos,

		    int a1, int a2, int b1, int b2, struct hunklist *l)

{

	int i, j, k;

	/* find the longest match in this chunk */

	k = longest_match(a, b, pos, a1, a2, b1, b2, &i, &j);

	if (!k)

		return;

	/* and recurse on the remaining chunks on either side */

	recurse(a, b, pos, a1, i, b1, j, l);

	l->head->a1 = i;

	l->head->a2 = i + k;

	l->head->b1 = j;

	l->head->b2 = j + k;

	l->head++;

	recurse(a, b, pos, i + k, a2, j + k, b2, l);

}

static struct hunklist diff(struct line *a, int an, struct line *b, int bn)

{

	struct hunklist l;

	struct hunk *curr;

	struct pos *pos;

	int t;

	/* allocate and fill arrays */

	t = equatelines(a, an, b, bn);

	pos = (struct pos *)calloc(bn ? bn : 1, sizeof(struct pos));

	/* we can't have more matches than lines in the shorter file */

	l.head = l.base = (struct hunk *)malloc(sizeof(struct hunk) *

	                                        ((an<bn ? an:bn) + 1));

	if (pos && l.base && t) {

		/* generate the matching block list */

		recurse(a, b, pos, 0, an, 0, bn, &l);

		l.head->a1 = l.head->a2 = an;

		l.head->b1 = l.head->b2 = bn;

		l.head++;

	}

	free(pos);

	/* normalize the hunk list, try to push each hunk towards the end */

	for (curr = l.base; curr != l.head; curr++) {

		struct hunk *next = curr+1;

		int shift = 0;

		if (next == l.head)

			break;

		if (curr->a2 == next->a1)

			while (curr->a2+shift < an && curr->b2+shift < bn

			       && !cmp(a+curr->a2+shift, b+curr->b2+shift))

				shift++;

		else if (curr->b2 == next->b1)

			while (curr->b2+shift < bn && curr->a2+shift < an

			       && !cmp(b+curr->b2+shift, a+curr->a2+shift))

				shift++;

		if (!shift)

			continue;

		curr->b2 += shift;

		next->b1 += shift;

		curr->a2 += shift;

		next->a1 += shift;

	}

	return l;

}

//--

// TODO: implement the r_diff_lines // we need to implement r_file_line_at (file, off);

R_API int r_diff_buffers_delta(RDiff *d, const ut8 *sa, int la, const ut8 *sb, int lb) {

	RDiffOp dop;

	struct line *al, *bl;

	struct hunklist l = { NULL, NULL };

	struct hunk *h;

	int an, bn, offa, rlen, offb, len = 0;

	int hits = 0;

	an = splitlines((const char *)sa, la, &al);

	bn = splitlines((const char*)sb, lb, &bl);

	if (!al || !bl) {

		eprintf ("bindiff_buffers: Out of memory.\n");

		return -1;

	}

	l = diff (al, an, bl, bn);

	if (!l.head) {

		eprintf ("bindiff_buffers: Out of memory.\n");

		return -1;

	}

	la = lb = 0;

	for (h = l.base; h != l.head; h++) {

		if (h->a1 != la || h->b1 != lb) {

			len = bl[h->b1].l - bl[lb].l;

			offa = al[la].l - al->l;

			offb = al[h->a1].l - al->l;

			rlen = offb-offa;

			if (d->callback) {

				/* source file */

				dop.a_off = offa;

				dop.a_buf = (ut8 *)al[la].l;

				dop.a_len = rlen;

				/* destination file */

				dop.b_off = offa; // XXX offb not used??

				dop.b_buf = (ut8 *)bl[lb].l;

				dop.b_len = len;

				if (!d->callback (d, d->user, &dop))

					break;

			}

#if 0	

			if (rlen > 0) {

				//printf ("Remove %d bytes at %d\n", rlen, offa);

				printf ("r-%d @ 0x%"PFMT64x"\n", rlen, (ut64)offa);

			}

			printf ("e file.write=true\n"); // XXX

			printf ("wx ");

			for(i=0;i<len;i++)

				printf ("%02x", bl[lb].l[i]);

			printf (" @ 0x%"PFMT64x"\n", (ut64)offa);

			rb += 12 + len;

#endif

		}

		la = h->a2;

		lb = h->b2;

	}

	free (al);

	free (bl);

	free (l.base);

	return hits;

}