/* retoor <retoor@molodetz.nl> */
#include "repl.h"
#include "loreg.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_INPUT 4096

static void print_banner(void) {
    printf("loreg v%s - regex interpreter\n", LOREG_VERSION);
    printf("commands: :q quit, :h help, :p <pattern> set pattern, :m <text> match, :s <text> search\n\n");
}

static void print_help(void) {
    printf("loreg REPL commands:\n");
    printf("  :q          quit\n");
    printf("  :h          show this help\n");
    printf("  :p <regex>  compile and set pattern\n");
    printf("  :m <text>   match text against pattern (anchored)\n");
    printf("  :s <text>   search for pattern in text\n");
    printf("  <text>      search for pattern in text\n\n");
    printf("regex syntax:\n");
    printf("  .           any character\n");
    printf("  *           zero or more\n");
    printf("  +           one or more\n");
    printf("  ?           zero or one\n");
    printf("  |           alternation\n");
    printf("  ()          grouping\n");
    printf("  []          character class\n");
    printf("  [^]         negated class\n");
    printf("  ^           start anchor\n");
    printf("  $           end anchor\n");
    printf("  {n}         exactly n\n");
    printf("  {n,}        n or more\n");
    printf("  {n,m}       n to m\n");
    printf("  \\d          digit\n");
    printf("  \\w          word character\n");
    printf("  \\s          whitespace\n");
    printf("  \\D \\W \\S    negated classes\n\n");
}

static void print_match(const char *text, loreg_match_t *result) {
    if (!result->matched) {
        printf("no match\n");
        return;
    }

    printf("match: \"");
    for (size_t i = result->match_start; i < result->match_end; i++) {
        printf("%c", text[i]);
    }
    printf("\" [%zu-%zu]\n", result->match_start, result->match_end);

    for (size_t i = 0; i < result->group_count; i++) {
        if (result->groups[i].matched) {
            printf("  group %zu: \"", i);
            for (size_t j = result->groups[i].start; j < result->groups[i].end; j++) {
                printf("%c", text[j]);
            }
            printf("\" [%zu-%zu]\n", result->groups[i].start, result->groups[i].end);
        }
    }
}

static char *read_line(void) {
    static char buffer[MAX_INPUT];
    printf("> ");
    fflush(stdout);

    if (!fgets(buffer, MAX_INPUT, stdin)) {
        return NULL;
    }

    size_t len = strlen(buffer);
    if (len > 0 && buffer[len - 1] == '\n') {
        buffer[len - 1] = '\0';
    }

    return buffer;
}

void repl_run(void) {
    print_banner();

    loreg_regex_t *regex = NULL;
    char *line;

    while ((line = read_line()) != NULL) {
        if (strlen(line) == 0) continue;

        if (strcmp(line, ":q") == 0 || strcmp(line, ":quit") == 0) {
            break;
        }

        if (strcmp(line, ":h") == 0 || strcmp(line, ":help") == 0) {
            print_help();
            continue;
        }

        if (strncmp(line, ":p ", 3) == 0) {
            const char *pattern = line + 3;
            while (*pattern == ' ') pattern++;

            if (regex) {
                loreg_free(regex);
                regex = NULL;
            }

            loreg_error_t error;
            regex = loreg_compile(pattern, &error);
            if (!regex) {
                printf("error: %s\n", loreg_error_string(error));
            } else {
                printf("pattern compiled: %s\n", pattern);
            }
            continue;
        }

        if (strncmp(line, ":m ", 3) == 0) {
            if (!regex) {
                printf("error: no pattern set (use :p <pattern>)\n");
                continue;
            }

            const char *text = line + 3;
            while (*text == ' ') text++;

            loreg_match_t result;
            loreg_match(regex, text, &result);
            print_match(text, &result);
            continue;
        }

        if (strncmp(line, ":s ", 3) == 0) {
            if (!regex) {
                printf("error: no pattern set (use :p <pattern>)\n");
                continue;
            }

            const char *text = line + 3;
            while (*text == ' ') text++;

            loreg_match_t result;
            loreg_search(regex, text, &result);
            print_match(text, &result);
            continue;
        }

        if (line[0] == ':') {
            printf("unknown command: %s\n", line);
            continue;
        }

        if (!regex) {
            printf("error: no pattern set (use :p <pattern>)\n");
            continue;
        }

        loreg_match_t result;
        loreg_search(regex, line, &result);
        print_match(line, &result);
    }

    if (regex) {
        loreg_free(regex);
    }

    printf("\n");
}