static double calc_score_for_char(MatchInfo *m, UChar32 last, UChar32 current, int32_t distance_from_last_match) {
double factor = 1.0;
double ans = m->max_score_per_char;
if (u_strchr32(m->level1, last) != NULL)
factor = 0.9;
else if (u_strchr32(m->level2, last) != NULL)
factor = 0.8;
else if (u_isULowercase(last) && u_isUUppercase(current))
factor = 0.8; // CamelCase
else if (u_strchr32(m->level3, last) != NULL)
factor = 0.7;
else
// If last is not a special char, factor diminishes
// as distance from last matched char increases
factor = (1.0 / distance_from_last_match) * 0.75;
return ans * factor;
}
static double process_item(MatchInfo *m, Stack *stack, int32_t *final_positions) {
UChar32 nc, hc, lc;
UChar *p;
double final_score = 0.0, score = 0.0, score_for_char = 0.0;
int32_t pos, i, j, hidx, nidx, last_idx, distance, *positions = final_positions + m->needle_len;
MemoryItem mem = {0};
stack_push(stack, 0, 0, 0, 0.0, final_positions);
while (stack->pos >= 0) {
stack_pop(stack, &hidx, &nidx, &last_idx, &score, positions);
mem = m->memo[hidx][nidx][last_idx];
if (mem.score == DBL_MAX) {
// No memoized result, calculate the score
for (i = nidx; i < m->needle_len;) {
nidx = i;
U16_NEXT(m->needle, i, m->needle_len, nc); // i now points to next char in needle
if (m->haystack_len - hidx < m->needle_len - nidx) { score = 0.0; break; }
p = u_strchr32(m->haystack + hidx, nc); // TODO: Use primary collation for the find
if (p == NULL) { score = 0.0; break; }
pos = (int32_t)(p - m->haystack);
distance = u_countChar32(m->haystack + last_idx, pos - last_idx);
if (distance <= 1) score_for_char = m->max_score_per_char;
else {
U16_GET(m->haystack, 0, pos, m->haystack_len, hc);
j = pos;
U16_PREV(m->haystack, 0, j, lc); // lc is the prev character
score_for_char = calc_score_for_char(m, lc, hc, distance);
}
j = pos;
U16_NEXT(m->haystack, j, m->haystack_len, hc);
hidx = j;
if (m->haystack_len - hidx >= m->needle_len - nidx) stack_push(stack, hidx, nidx, last_idx, score, positions);
last_idx = pos;
positions[nidx] = pos;
score += score_for_char;
} // for(i) iterate over needle
mem.score = score; memcpy(mem.positions, positions, sizeof(*positions) * m->needle_len);
} else {
score = mem.score; memcpy(positions, mem.positions, sizeof(*positions) * m->needle_len);
}
// We have calculated the score for this hidx, nidx, last_idx combination, update final_score and final_positions, if needed
if (score > final_score) {
final_score = score;
memcpy(final_positions, positions, sizeof(*positions) * m->needle_len);
}
}
return final_score;
}
