// retoor <retoor@molodetz.nl>

#include "r_diff.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

#define COLOR_RED     "\x1b[31m"
#define COLOR_GREEN   "\x1b[32m"
#define COLOR_CYAN    "\x1b[36m"
#define COLOR_RESET   "\x1b[0m"
#define COLOR_DIM     "\x1b[2m"
#define COLOR_BG_RED  "\x1b[41;37m"
#define COLOR_BG_GREEN "\x1b[42;30m"

typedef struct {
    char **lines;
    size_t count;
} line_set_t;

static line_set_t split_lines(const char *str) {
    line_set_t set = {NULL, 0};
    if (!str || !*str) return set;

    char *copy = strdup(str);
    char *p = copy;
    char *line_start = copy;

    while (*p) {
        if (*p == '\n') {
            *p = '\0';
            set.lines = realloc(set.lines, sizeof(char *) * (set.count + 1));
            set.lines[set.count++] = strdup(line_start);
            line_start = p + 1;
        }
        p++;
    }
    // Handle last line if no trailing newline
    if (*line_start) {
        set.lines = realloc(set.lines, sizeof(char *) * (set.count + 1));
        set.lines[set.count++] = strdup(line_start);
    }
    
    free(copy);
    return set;
}

static void free_line_set(line_set_t set) {
    for (size_t i = 0; i < set.count; i++) free(set.lines[i]);
    free(set.lines);
}

static void print_truncated(const char *str, int width, const char *color) {
    if (width <= 0) return;
    int len = (int)strlen(str);
    if (color) printf("%s", color);
    
    if (len > width && width > 3) {
        char *temp = strndup(str, (size_t)width - 3);
        printf("%s...", temp);
        free(temp);
    } else {
        printf("%-*.*s", width, width, str);
    }
    
    if (color) printf("%s", COLOR_RESET);
}

void r_diff_print(const char *path, const char *old_content, const char *new_content) {
    line_set_t old_set = split_lines(old_content);
    line_set_t new_set = split_lines(new_content);

    struct winsize w;
    ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
    int term_width = w.ws_col > 0 ? w.ws_col : 120;
    if (term_width < 40) term_width = 40; // Minimum usable width
    int col_width = (term_width - 15) / 2;
    if (col_width < 5) col_width = 5;

    printf("\n%s %s CHANGES: %s %s\n", COLOR_CYAN, COLOR_DIM, path, COLOR_RESET);
    printf("%4s %-*s | %4s %-*s\n", "LINE", col_width, " OLD", "LINE", col_width, " NEW");
    printf("%.*s\n", term_width, "--------------------------------------------------------------------------------------------------------------------------------------------");

    size_t o = 0, n = 0;
    while (o < old_set.count || n < new_set.count) {
        bool match = false;
        if (o < old_set.count && n < new_set.count) {
            if (strcmp(old_set.lines[o], new_set.lines[n]) == 0) {
                printf("%4zu   ", o + 1);
                print_truncated(old_set.lines[o], col_width - 2, NULL);
                printf(" | %4zu   ", n + 1);
                print_truncated(new_set.lines[n], col_width - 2, NULL);
                printf("\n");
                o++; n++;
                match = true;
            }
        }

        if (!match) {
            bool found_o_later = false;
            if (o < old_set.count) {
                for (size_t i = n + 1; i < new_set.count && i < n + 5; i++) {
                    if (strcmp(old_set.lines[o], new_set.lines[i]) == 0) {
                        found_o_later = true;
                        break;
                    }
                }
            }

            if (found_o_later) {
                // Line added on NEW side
                printf("%4s   ", "");
                print_truncated("", col_width - 2, NULL);
                printf(" | %4zu %s+%s ", n + 1, COLOR_GREEN, COLOR_RESET);
                print_truncated(new_set.lines[n], col_width - 2, COLOR_GREEN);
                printf("\n");
                n++;
            } else if (o < old_set.count) {
                // Line removed on OLD side
                printf("%4zu %s-%s ", o + 1, COLOR_RED, COLOR_RESET);
                print_truncated(old_set.lines[o], col_width - 2, COLOR_RED);
                printf(" | %4s   ", "");
                print_truncated("", col_width - 2, NULL);
                printf("\n");
                o++;
            } else if (n < new_set.count) {
                // Line added on NEW side
                printf("%4s   ", "");
                print_truncated("", col_width - 2, NULL);
                printf(" | %4zu %s+%s ", n + 1, COLOR_GREEN, COLOR_RESET);
                print_truncated(new_set.lines[n], col_width - 2, COLOR_GREEN);
                printf("\n");
                n++;
            }
        }
        fflush(stdout);
        usleep(30000); // 30ms delay for streaming effect
    }
    printf("\n");
    fflush(stdout);

    free_line_set(old_set);
    free_line_set(new_set);
}