#include "bytecode.h"
#include "value.h"
#include "vm.h"
#include "parser.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#ifndef FUN_VERSION
#define FUN_VERSION "0.0.0-dev"
#endif

static int is_blank_line(const char *s) {
    for (const char *p = s; *p; ++p) {
        if (*p != ' ' && *p != '\t' && *p != '\r' && *p != '\n') return 0;
    }
    return 1;
}

static void print_usage(const char *prog) {
    printf("Fun %s\n", FUN_VERSION);
    printf("Usage:\n");
    printf("  %s [script.fun]\n", prog ? prog : "fun");
    printf("  %s --help | -h\n", prog ? prog : "fun");
    printf("  %s --version | -V\n", prog ? prog : "fun");
    printf("\n");
    printf("When no script is provided, a REPL starts. Submit an empty line to execute the buffer.\n");
}

int main(int argc, char **argv) {
    VM vm;
    vm_init(&vm);

    // CLI flags
    if (argc > 1) {
        const char *arg = argv[1];
        if (strcmp(arg, "--help") == 0 || strcmp(arg, "-h") == 0) {
            print_usage(argv[0]);
            return 0;
        }
        if (strcmp(arg, "--version") == 0 || strcmp(arg, "-V") == 0) {
            printf("Fun %s\n", FUN_VERSION);
            return 0;
        }
    }

    // If a script path is provided, parse and run it
    if (argc > 1) {
        const char *path = argv[1];
        Bytecode *bc = parse_file_to_bytecode(path);
        if (!bc) {
            fprintf(stderr, "Failed to compile script: %s\n", path);
            return 1;
        }
        vm_run(&vm, bc);

        // Print captured output for user scripts
        vm_print_output(&vm);
        vm_clear_output(&vm);

        bytecode_free(bc);
        return 0;
    }

    // REPL mode
    printf("Fun REPL. Type code and press Enter. Submit an empty line to run.\n");
    printf("Commands: :help, :reset, :dump, :quit\n");
    char *buffer = NULL;
    size_t bufcap = 0;
    size_t buflen = 0;

#ifdef FUN_DEBUG
    // Open history file for appending
    const char *home = getenv("HOME");
    char hist_path[1024];
    FILE *hist = NULL;
    if (home) {
        snprintf(hist_path, sizeof(hist_path), "%s/.fun_history", home);
        hist = fopen(hist_path, "a");
    }
#endif

    for (;;) {
        fputs(buflen == 0 ? "fun> " : "... ", stdout);
        fflush(stdout);

        char line[4096];
        if (!fgets(line, sizeof(line), stdin)) {
            puts("");
            break; // EOF
        }

        // Single-line commands when buffer is empty
        if (buflen == 0 && line[0] == ':') {
            if (strncmp(line, ":quit", 5) == 0) break;
            if (strncmp(line, ":help", 5) == 0) {
                printf("Commands: :help, :reset, :dump, :quit\n");
                continue;
            }
            if (strncmp(line, ":reset", 6) == 0) {
                vm_reset(&vm);
                printf("VM state reset.\n");
                continue;
            }
            if (strncmp(line, ":dump", 5) == 0) {
                vm_dump_globals(&vm);
                continue;
            }
            printf("Unknown command. Use :help\n");
            continue;
        }

        // Empty line -> compile and run accumulated buffer
        if (is_blank_line(line)) {
            if (buflen == 0) continue; // ignore extra empty lines
            // Null-terminate
            if (buflen + 1 >= bufcap) {
                bufcap = buflen + 1;
                buffer = (char*)realloc(buffer, bufcap);
            }
            buffer[buflen] = '\0';

            Bytecode *bc = parse_string_to_bytecode(buffer);
            if (bc) {
                vm_run(&vm, bc);
                vm_print_output(&vm);
                vm_clear_output(&vm);
                bytecode_free(bc);
#ifdef FUN_DEBUG
                if (hist) {
                    fprintf(hist, "%s\n", buffer);
                    fflush(hist);
                }
#endif
            } else {
                // Better error message with caret
                int line_no = 0, col_no = 0;
                char emsg[256];
                if (parser_last_error(emsg, sizeof(emsg), &line_no, &col_no)) {
                    printf("Parse error at %d:%d: %s\n", line_no, col_no, emsg);
                    // Print the offending line and caret
                    int cur_line = 1;
                    const char *p = buffer;
                    while (*p && cur_line < line_no) {
                        if (*p == '\n') cur_line++;
                        p++;
                    }
                    const char *line_start = p;
                    while (*p && *p != '\n') p++;
                    fwrite(line_start, 1, (size_t)(p - line_start), stdout);
                    printf("\n");
                    for (int i = 1; i < col_no; ++i) putchar(' ');
                    printf("^\n");
                } else {
                    printf("Parse error.\n");
                }
            }
            // reset buffer
            buflen = 0;
            continue;
        }

        // Append line to buffer
        size_t linelen = strlen(line);
        if (buflen + linelen + 1 > bufcap) {
            size_t newcap = bufcap == 0 ? 1024 : bufcap * 2;
            while (newcap < buflen + linelen + 1) newcap *= 2;
            buffer = (char*)realloc(buffer, newcap);
            bufcap = newcap;
        }
        memcpy(buffer + buflen, line, linelen);
        buflen += linelen;
    }

#ifdef FUN_DEBUG
    if (hist) fclose(hist);
#endif

    free(buffer);
    return 0;
}