#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <ctype.h>
#include "similarity_search.h"

// Case insensitive string comparison
int str_case_cmp(const char *s1, const char *s2) {
    while (*s1 && *s2) {
        int c1 = tolower((unsigned char)*s1);
        int c2 = tolower((unsigned char)*s2);
        if (c1 != c2) {
            return c1 - c2;
        }
        s1++;
        s2++;
    }
    return tolower((unsigned char)*s1) - tolower((unsigned char)*s2);
}

// Split a string into words
int split_into_words(const char *string, char *words[MAX_WORDS]) {
    if (!string || strlen(string) >= MAX_STRING_LEN) {
        return 0;
    }
    
    char temp[MAX_STRING_LEN];
    strncpy(temp, string, MAX_STRING_LEN - 1);
    temp[MAX_STRING_LEN - 1] = '\0';
    
    int word_count = 0;
    char *token = strtok(temp, " \t\n");
    
    while (token != NULL && word_count < MAX_WORDS) {
        words[word_count] = strdup(token);
        if (!words[word_count]) {
            // Free any already allocated words on error
            for (int i = 0; i < word_count; i++) {
                free(words[i]);
            }
            return 0;
        }
        word_count++;
        token = strtok(NULL, " \t\n");
    }
    
    return word_count;
}

// Free memory allocated for words
void free_words(char *words[], int word_count) {
    for (int i = 0; i < word_count; i++) {
        free(words[i]);
    }
}

// Calculate similarity between two words based on character matching
float word_similarity(const char *word1, const char *word2) {
    int len1 = strlen(word1);
    int len2 = strlen(word2);
    
    // For very short words (3 chars or less), require exact match
    if (len1 <= 3 || len2 <= 3) {
        return str_case_cmp(word1, word2) == 0 ? 1.0f : 0.0f;
    }
    
    int max_len = len1 > len2 ? len1 : len2;
    if (max_len == 0) return 0.0f;
    
    // Count matching characters (case insensitive)
    int matches = 0;
    int i = 0, j = 0;
    
    while (i < len1 && j < len2) {
        if (tolower((unsigned char)word1[i]) == tolower((unsigned char)word2[j])) {
            matches++;
            i++;
            j++;
        } else if (tolower((unsigned char)word1[i]) < tolower((unsigned char)word2[j])) {
            i++;
        } else {
            j++;
        }
    }
    
    // Calculate similarity based on matching characters
    float char_similarity = (float)matches / max_len;
    
    // Require higher similarity for shorter words
    float min_similarity = 0.7f; // Default minimum
    if (len1 <= 5 || len2 <= 5) {
        min_similarity = 0.9f; // Higher requirement for short words
    }
    
    // If similarity is below minimum, return 0
    if (char_similarity < min_similarity) {
        return 0.0f;
    }
    
    // If words are the same length, give a small boost
    if (len1 == len2) {
        char_similarity = char_similarity * 1.1f; // 10% boost for same length
        if (char_similarity > 1.0f) char_similarity = 1.0f;
    }
    
    return char_similarity;
}

// Calculate similarity between query and target string
float calculate_similarity(const char *query, const char *target, float cutoff) {
    // Split strings into words
    char *query_words[MAX_WORDS] = {0};
    char *target_words[MAX_WORDS] = {0};
    
    int query_word_count = split_into_words(query, query_words);
    int target_word_count = split_into_words(target, target_words);
    
    if (query_word_count == 0 || target_word_count == 0) {
        free_words(query_words, query_word_count);
        free_words(target_words, target_word_count);
        return 0.0;
    }
    
    // Track best matches for each query word
    float best_word_similarities[MAX_WORDS] = {0.0f};
    int query_words_found = 0;
    
    // For each query word, find its best match in target words
    for (int i = 0; i < query_word_count; i++) {
        float best_similarity = 0.0f;
        
        for (int j = 0; j < target_word_count; j++) {
            float similarity = word_similarity(query_words[i], target_words[j]);
            if (similarity > best_similarity) {
                best_similarity = similarity;
            }
        }
        
        best_word_similarities[i] = best_similarity;
        if (best_similarity >= 0.8f) { // Consider it a match if similarity is high enough
            query_words_found++;
        }
    }
    
    // Calculate overall similarity
    float word_match_score = (float)query_words_found / query_word_count;
    
    // Calculate average of best word similarities
    float avg_word_similarity = 0.0f;
    for (int i = 0; i < query_word_count; i++) {
        avg_word_similarity += best_word_similarities[i];
    }
    avg_word_similarity /= query_word_count;
    
    // Combine scores: 70% weight on word matches, 30% on character similarity
    float similarity = (word_match_score * 0.7f) + (avg_word_similarity * 0.3f);
    
    // If all query words were found with high similarity, ensure high overall score
    if (query_words_found == query_word_count && avg_word_similarity >= 0.8f) {
        similarity = 1.0f; // Perfect match
    }
    
    free_words(query_words, query_word_count);
    free_words(target_words, target_word_count);
    
    return similarity;
}

// Compare function for qsort to sort results by similarity (descending)
int compare_results(const void *a, const void *b) {
    const SearchResult *result_a = (const SearchResult *)a;
    const SearchResult *result_b = (const SearchResult *)b;
    
    if (result_b->similarity > result_a->similarity) return 1;
    if (result_b->similarity < result_a->similarity) return -1;
    return 0;
}

// Generate a random word
void generate_random_word(char *word, int max_len) {
    int len = 3 + rand() % 8; // Random length between 3 and 10
    for (int i = 0; i < len; i++) {
        word[i] = 'a' + (rand() % 26);
    }
    word[len] = '\0';
}

// Generate a random string consisting of multiple words
void generate_random_string(char *string, int max_len) {
    if (!string || max_len <= 0) {
        return;
    }
    
    int num_words = 2 + rand() % 5; // Random number of words between 2 and 6
    string[0] = '\0';
    size_t current_len = 0;
    
    for (int i = 0; i < num_words; i++) {
        char word[20];
        generate_random_word(word, sizeof(word) - 1);
        
        size_t word_len = strlen(word);
        size_t space_needed = word_len + (i > 0 ? 1 : 0); // +1 for space if not first word
        
        if (current_len + space_needed < (size_t)max_len - 1) {
            if (i > 0) {
                strncat(string, " ", max_len - current_len - 1);
                current_len++;
            }
            strncat(string, word, max_len - current_len - 1);
            current_len += word_len;
        } else {
            break;
        }
    }
}

// Create a new search index
SearchIndex* create_search_index(int capacity) {
    if (capacity <= 0) return NULL;
    
    SearchIndex* index = (SearchIndex*)malloc(sizeof(SearchIndex));
    if (!index) return NULL;
    
    index->strings = (char**)malloc(capacity * sizeof(char*));
    if (!index->strings) {
        free(index);
        return NULL;
    }
    
    index->num_strings = 0;
    index->capacity = capacity;
    return index;
}

// Add a string to the index
int add_string_to_index(SearchIndex* index, const char* string) {
    if (!index || !string) return -1;
    
    // Check if we've reached capacity
    if (index->num_strings >= index->capacity) {
        return -1;
    }
    
    // Check if string is too long
    if (strlen(string) >= MAX_STRING_LEN) {
        return -1;
    }
    
    index->strings[index->num_strings] = strdup(string);
    if (!index->strings[index->num_strings]) return -1;
    
    index->num_strings++;
    return 0;
}

// Free the search index and all associated memory
void free_search_index(SearchIndex* index) {
    if (!index) return;
    
    for (int i = 0; i < index->num_strings; i++) {
        free(index->strings[i]);
    }
    
    free(index->strings);
    free(index);
}

// Search the index with the given query and similarity cutoff
SearchResult* search_index(SearchIndex* index, const char* query, float cutoff, int* num_results) {
    if (!index || !query || !num_results) return NULL;
    
    // Validate input string length
    if (strlen(query) >= MAX_STRING_LEN) {
        *num_results = 0;
        return NULL;
    }
    
    // Validate cutoff
    if (cutoff < 0.0f || cutoff > 1.0f) {
        *num_results = 0;
        return NULL;
    }
    
    // Allocate temporary array for results
    SearchResult* temp_results = (SearchResult*)malloc(index->num_strings * sizeof(SearchResult));
    if (!temp_results) return NULL;
    
    *num_results = 0;
    
    // Search through all strings in the index
    for (int i = 0; i < index->num_strings; i++) {
        float similarity = calculate_similarity(query, index->strings[i], cutoff);
        
        if (similarity >= cutoff) {
            // Store a copy of the string in the result
            temp_results[*num_results].string = strdup(index->strings[i]);
            if (!temp_results[*num_results].string) {
                // Free any already allocated strings on error
                for (int j = 0; j < *num_results; j++) {
                    free(temp_results[j].string);
                }
                free(temp_results);
                return NULL;
            }
            temp_results[*num_results].similarity = similarity;
            (*num_results)++;
        }
    }
    
    // Sort results by similarity
    qsort(temp_results, *num_results, sizeof(SearchResult), compare_results);
    
    // Allocate final result array with exact size
    SearchResult* results = (SearchResult*)malloc(*num_results * sizeof(SearchResult));
    if (!results) {
        // Free all strings in temp_results
        for (int i = 0; i < *num_results; i++) {
            free(temp_results[i].string);
        }
        free(temp_results);
        return NULL;
    }
    
    // Copy results to final array
    for (int i = 0; i < *num_results; i++) {
        results[i].string = temp_results[i].string;
        results[i].similarity = temp_results[i].similarity;
    }
    free(temp_results);
    
    return results;
}

// Free the search results
void free_search_results(SearchResult* results, int num_results) {
    if (!results) return;
    
    // Free all strings in the results
    for (int i = 0; i < num_results; i++) {
        free(results[i].string);
    }
    free(results);
}