// User application entry points for shell_win32.

#include <windows.h>
#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#include <string.h>

#define MAX_CMD 256
static HANDLE hIn = INVALID_HANDLE_VALUE;
static HANDLE hOut = INVALID_HANDLE_VALUE;

// External/Custom API.
BOOL ClearConsoleScreenBuffer(HANDLE hConsole);

// --- Output Helpers ---.
static void print(const char* s) {
    DWORD written;
    if (hOut != INVALID_HANDLE_VALUE) WriteConsoleA(hOut, s, (DWORD)strlen(s), &written, 0);
    else OutputDebugStringA(s);
}

// Prints u Int.
static void printUInt(uint32_t n) {
    char buf[12]; int i = 0;
    if (n == 0) { print("0"); return; }
    while (n > 0) { buf[i++] = (char)('0' + n % 10); n /= 10; }
    while (i > 0) { char c[2] = { buf[--i], '\0' }; print(c); }
}

// Prints int.
static void printInt(int32_t n) {
    if (n < 0) { print("-"); n = -n; }
    printUInt((uint32_t)n);
}

// --- Line Editor ---.
static void readLine(char* buf, int len) {
    int pos = 0;
    while (true) {
        char c; DWORD nRead;
        ReadConsoleA(hIn, &c, 1, &nRead, 0);
        if (!nRead) continue;
        if (c == '\r' || c == '\n') { print("\n"); break; }
        if ((c == '\b' || c == 127) && pos > 0) { pos--; print("\b \b"); continue; }
        if (c < 0x20 || c == 127) continue;
        if (pos < len - 1) {
            buf[pos++] = c;
            char echo[2] = { c, '\0' };
            print(echo);
        }
    }
    buf[pos] = '\0';
}

// Implements the trim operation.
static char* trim(char* s) {
    while (*s == ' ') s++;
    int len = (int)strlen(s);
    while (len > 0 && s[len - 1] == ' ') len--;
    s[len] = '\0';
    return s;
}

// --- Built-in Commands ---.
static void cmd_help() {
    print("Available commands:\n"
          "  help              - Show this list\n"
          "  dir [path]        - List directory contents\n"
          "  cd <path>         - Change directory\n"
          "  type <file>       - Display file contents\n"
          "  del <file>        - Delete a file\n"
          "  write <file> <tx> - Create a file with text\n"
          "  clear             - Clear the screen\n"
          "  exit              - Close the shell\n");
}

// Implements the cmd write operation.
static void cmd_write(const char* args) {
    char filename[MAX_PATH]; int i = 0;
    while (args[i] != ' ' && args[i] != '\0' && i < MAX_PATH - 1) {
        filename[i] = args[i]; i++;
    }
    filename[i] = '\0';
    if (args[i] == '\0' || args[i+1] == '\0') {
        print("write: usage: write <filename> <text>\n");
        return;
    }
    HANDLE hFile = CreateFileA(filename, GENERIC_WRITE, 0, 0, CREATE_ALWAYS, 0, 0);
    if (hFile == INVALID_HANDLE_VALUE) { print("write: could not create file\n"); return; }
    DWORD written;
    WriteFile(hFile, args + i + 1, (DWORD)strlen(args + i + 1), &written, 0);
    CloseHandle(hFile);
    print("File written successfully.\n");
}

// Implements the cmd dir operation.
static void cmd_dir(const char* path) {
    WIN32_FIND_DATAA fd;
    char search_path[MAX_PATH];
    const char* target = (path && *path != '\0') ? path : ".";
    
    size_t len = strlen(target);
    if (len + 3 > MAX_PATH) { print("dir: path too long\n"); return; }
    strcpy(search_path, target);
    strcat(search_path, "\\*");

    HANDLE hFind = FindFirstFileA(search_path, &fd);
    if (hFind == INVALID_HANDLE_VALUE) { print("dir: failed to read directory\n"); return; }
    do {
        print(fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY ? "<DIR> " : "      ");
        print(fd.cFileName); print("\n");
    } while (FindNextFileA(hFind, &fd));
    FindClose(hFind);
}

// Implements the cmd type operation.
static void cmd_type(const char* filename) {
    HANDLE hFile = CreateFileA(filename, GENERIC_READ, FILE_SHARE_READ, 0, OPEN_EXISTING, 0, 0);
    if (hFile == INVALID_HANDLE_VALUE) { print("type: cannot open file\n"); return; }
    char buffer[512]; DWORD bytesRead;
    while (ReadFile(hFile, buffer, sizeof(buffer) - 1, &bytesRead, 0) && bytesRead > 0) {
        buffer[bytesRead] = '\0'; print(buffer);
    }
    CloseHandle(hFile); print("\n");
}

// Runs command.
static int runCommand(const char* cmd) {
    if (!cmd || *cmd == '\0') return 0;
    if (strcmp(cmd, "exit") == 0) return 1;
    if (strcmp(cmd, "help") == 0) { cmd_help(); return 0; }
    if (strcmp(cmd, "clear") == 0) { ClearConsoleScreenBuffer(hOut); return 0; }
    if (strcmp(cmd, "crash") == 0) { *(int*)0 = 42; return 0; }
    if (strcmp(cmd, "dir") == 0) { cmd_dir("."); return 0; }
    if (strncmp(cmd, "dir ", 4) == 0) { cmd_dir(cmd + 4); return 0; }
    if (strncmp(cmd, "cd ", 3) == 0) { if (!SetCurrentDirectoryA(cmd + 3)) print("cd: failed\n"); return 0; }
    if (strncmp(cmd, "del ", 4) == 0) { DeleteFileA(cmd + 4); return 0; }
    if (strncmp(cmd, "type ", 5) == 0) { cmd_type(cmd + 5); return 0; }
    if (strncmp(cmd, "write ", 6) == 0) { cmd_write(cmd + 6); return 0; }

    PROCESS_INFORMATION pi;
    char cmdBuf[MAX_CMD];
    strncpy(cmdBuf, cmd, MAX_CMD - 1);
    cmdBuf[MAX_CMD - 1] = '\0';
    if (CreateProcessA(NULL, cmdBuf, NULL, NULL, FALSE, 0, NULL, NULL, NULL, &pi)) {
        WaitForSingleObject(pi.hProcess, INFINITE);
        if (pi.hThread && pi.hThread != INVALID_HANDLE_VALUE)
            CloseHandle(pi.hThread);
        if (pi.hProcess && pi.hProcess != INVALID_HANDLE_VALUE)
            CloseHandle(pi.hProcess);
        FlushConsoleInputBuffer(hIn);
    } else {
        print("shell: launch failed\n");
    }
    return 0;
}

// Runs the requested operation.
int main(void) {
    hIn = GetStdHandle(STD_INPUT_HANDLE);
    hOut = GetStdHandle(STD_OUTPUT_HANDLE);

    const char* cmdline = GetCommandLineA();
    char lineBuf[MAX_CMD];

    print("shell: command line: ");
    print(cmdline);
    print("\n");
    print("shell: ready\n");
    while (true) {
        print("> ");
        readLine(lineBuf, MAX_CMD);
        if (runCommand(trim(lineBuf))) break;
    }
    print("shell: goodbye\n");
    ExitProcess(0);
}