#include "wren.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef _WIN32
#include <windows.h>
#else
#include <sys/stat.h>
#endif

// Helper to validate that the value in a slot is a string.
static bool io_validate_string(WrenVM* vm, int slot, const char* name) {
    if (wrenGetSlotType(vm, slot) == WREN_TYPE_STRING) return true;
    // The error is placed in slot 0, which becomes the return value.
    wrenSetSlotString(vm, 0, "Argument must be a string.");
    wrenAbortFiber(vm, 0);
    return false;
}

// --- File Class Foreign Methods ---

void fileExists(WrenVM* vm) {
    if (!io_validate_string(vm, 1, "path")) return;
    const char* path = wrenGetSlotString(vm, 1);

#ifdef _WIN32
    DWORD attrib = GetFileAttributes(path);
    wrenSetSlotBool(vm, 0, (attrib != INVALID_FILE_ATTRIBUTES && !(attrib & FILE_ATTRIBUTE_DIRECTORY)));
#else
    struct stat buffer;
    wrenSetSlotBool(vm, 0, (stat(path, &buffer) == 0));
#endif
}

void fileDelete(WrenVM* vm) {
    if (!io_validate_string(vm, 1, "path")) return;
    const char* path = wrenGetSlotString(vm, 1);

    if (remove(path) == 0) {
        wrenSetSlotBool(vm, 0, true);
    } else {
        wrenSetSlotBool(vm, 0, false);
    }
}

void fileRead(WrenVM* vm) {
    if (!io_validate_string(vm, 1, "path")) return;
    const char* path = wrenGetSlotString(vm, 1);

    FILE* file = fopen(path, "rb");
    if (file == NULL) {
        wrenSetSlotNull(vm, 0);
        return;
    }

    fseek(file, 0L, SEEK_END);
    size_t fileSize = ftell(file);
    rewind(file);

    char* buffer = (char*)malloc(fileSize + 1);
    if (buffer == NULL) {
        fclose(file);
        wrenSetSlotString(vm, 0, "Could not allocate memory to read file.");
        wrenAbortFiber(vm, 0);
        return;
    }

    size_t bytesRead = fread(buffer, sizeof(char), fileSize, file);
    if (bytesRead < fileSize) {
        free(buffer);
        fclose(file);
        wrenSetSlotString(vm, 0, "Could not read entire file.");
        wrenAbortFiber(vm, 0);
        return;
    }

    buffer[bytesRead] = '\0';
    fclose(file);

    wrenSetSlotBytes(vm, 0, buffer, bytesRead);
    free(buffer);
}

void fileWrite(WrenVM* vm) {
    if (!io_validate_string(vm, 1, "path")) return;
    if (!io_validate_string(vm, 2, "contents")) return;

    const char* path = wrenGetSlotString(vm, 1);
    int length;
    const char* contents = wrenGetSlotBytes(vm, 2, &length);

    FILE* file = fopen(path, "wb");
    if (file == NULL) {
        wrenSetSlotBool(vm, 0, false);
        return;
    }

    size_t bytesWritten = fwrite(contents, sizeof(char), length, file);
    fclose(file);

    wrenSetSlotBool(vm, 0, bytesWritten == (size_t)length);
}

// --- FFI Binding ---

WrenForeignMethodFn bindIoForeignMethod(WrenVM* vm, const char* module, const char* className, bool isStatic, const char* signature) {
    if (strcmp(module, "io") != 0) return NULL;

    if (strcmp(className, "File") == 0 && isStatic) {
        if (strcmp(signature, "exists(_)") == 0) return fileExists;
        if (strcmp(signature, "delete(_)") == 0) return fileDelete;
        if (strcmp(signature, "read(_)") == 0) return fileRead;
        if (strcmp(signature, "write(_,_)") == 0) return fileWrite;
    }

    return NULL;
}