#include <ctype.h>
#include <string.h>
#include <strings.h>
#include <stdio.h>
#include <float.h>
#include <math.h>

#include "match.h"

int has_match(const char *needle, const char *haystack){
	while(*needle){
		char nch = tolower(*needle++);
		for(;;){
			char ch = *haystack++;
			if(!ch)
				return 0;
			else if(nch == tolower(ch))
				break;
		}
	}
	return 1;
}

#define max(a, b) (((a) > (b)) ? (a) : (b))
typedef double score_t;
#define SCORE_MAX INFINITY
#define SCORE_MIN -INFINITY

/* print one of the internal matrices */
void mat_print(score_t *mat, const char *needle, const char *haystack){
	int n = strlen(needle);
	int m = strlen(haystack);
	int i, j;
	fprintf(stderr, "    ");
	for(j = 0; j < m; j++){
		fprintf(stderr, "     %c", haystack[j]);
	}
	fprintf(stderr, "\n");
	for(i = 0; i < n; i++){
		fprintf(stderr, " %c |", needle[i]);
		for(j = 0; j < m; j++){
			score_t val = mat[i*m + j];
			if(val == SCORE_MIN){
				fprintf(stderr, "  -inf");
			}else{
				fprintf(stderr, " % .2f", val);
			}
		}
		fprintf(stderr, "\n");
	}
	fprintf(stderr, "\n\n");
}

double calculate_score(const char *needle, const char *haystack, size_t *positions){
	if(!*haystack || !*needle)
		return SCORE_MIN;

	int n = strlen(needle);
	int m = strlen(haystack);

	if(m > 1024){
		/*
		 * Unreasonably large candidate: return no score
		 * If it is a valid match it will still be returned, it will
		 * just be ranked below any reasonably sized candidates
		 */
		return SCORE_MIN;
	}

	score_t match_bonus[m];
	score_t D[n][m], M[n][m];

	/*
	 * D[][] Stores the best score for this position ending with a match.
	 * M[][] Stores the best possible score at this position.
	 */

#define SCORE_GAP_LEADING      -0.005
#define SCORE_GAP_TRAILING     -0.005
#define SCORE_GAP_INNER        -0.01
#define SCORE_MATCH_CONSECUTIVE 1.0
#define SCORE_MATCH_SLASH       0.9
#define SCORE_MATCH_WORD        0.8
#define SCORE_MATCH_CAPITAL     0.7
#define SCORE_MATCH_DOT         0.6

	/* Which positions are beginning of words */
	char last_ch = '\0';
	for(int i = 0; i < m; i++){
		char ch = haystack[i];

		score_t score = 0;
		if(isalnum(ch)){
			if(!last_ch || last_ch == '/'){
				score = SCORE_MATCH_SLASH;
			}else if(last_ch == '-' ||
					last_ch == '_' ||
					last_ch == ' ' ||
					(last_ch >= '0' && last_ch <= '9')){
				score = SCORE_MATCH_WORD;
			}else if(last_ch >= 'a' && last_ch <= 'z' &&
					ch >= 'A' && ch <= 'Z'){
				/* CamelCase */
				score = SCORE_MATCH_CAPITAL;
			}else if(last_ch == '.'){
				score = SCORE_MATCH_DOT;
			}
		}

		match_bonus[i] = score;
		last_ch = ch;
	}

	for(int i = 0; i < n; i++){
		double prev_score = SCORE_MIN;
		double gap_score = i == n-1 ? SCORE_GAP_TRAILING : SCORE_GAP_INNER;
		for(int j = 0; j < m; j++){
			score_t score = SCORE_MIN;
			if(tolower(needle[i]) == tolower(haystack[j])){
				if(!i){
					score = (j * SCORE_GAP_LEADING) + match_bonus[j];
				}else if(j){
					score = max(
						M[i-1][j-1] + match_bonus[j],

						/* consecutive match, doesn't stack with match_bonus */
						D[i-1][j-1] + SCORE_MATCH_CONSECUTIVE
						);
				}
			}
			D[i][j] = score;
			M[i][j] = prev_score = max(score, prev_score + gap_score);
		}
	}

#if 0
	fprintf(stderr, "\"%s\" =~ \"%s\"\n", needle, haystack);
	mat_print(&D[0][0], needle, haystack);
	mat_print(&M[0][0], needle, haystack);
	fprintf(stderr, "\n");
#endif

	/* backtrace to find the positions of optimal matching */
	if(positions){
		int match_required = 0;
		for(int i = n-1, j = m-1; i >= 0; i--){
			for(; j >= 0; j--){
				/*
				 * There may be multiple paths which result in
				 * the optimal weight.
				 *
				 * For simplicity, we will pick the first one
				 * we encounter, the latest in the candidate
				 * string.
				 */
				if(D[i][j] != SCORE_MIN && (match_required || D[i][j] == M[i][j])){
					/* If this score was determined using
					 * SCORE_MATCH_CONSECUTIVE, the
					 * previous character MUST be a match
					 */
					match_required = i && j && M[i][j] == D[i-1][j-1] + SCORE_MATCH_CONSECUTIVE;
					positions[i] = j--;
					break;
				}
			}
		}
	}

	return M[n-1][m-1];
}

double match_positions(const char *needle, const char *haystack, size_t *positions){
	if(!*needle){
		return SCORE_MAX;
	}else if(!strcasecmp(needle, haystack)){
		if(positions){
			int n = strlen(needle);
			for(int i = 0; i < n; i++)
				positions[i] = i;
		}
		return SCORE_MAX;
	}else{
		return calculate_score(needle, haystack, positions);
	}
}

double match(const char *needle, const char *haystack){
	return match_positions(needle, haystack, NULL);
}