#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#include <string.h>
#include <ntlite/syscall.h>

#define MAX_CMD 256
#define MAX_PIDS 64  // Maximum number of PIDs we will fetch at once

// External Syscall Prototypes
uint32_t SysGetProcessList(uint32_t* pidsOut, size_t maxCount, size_t* countOut);

// ---------------------------------------------------------------------------
// Output helpers
// ---------------------------------------------------------------------------
static void print(const char* s) { SYS_WRITE_CONSOLE_REQUEST req = { SysSvFromCstr(s) }; SysWriteConsole(&req); }

static uint32_t open_file(const char* path, uint32_t* handleOut) {
    SYS_PATH_HANDLE_REQUEST req = { SysSvFromCstr(path), handleOut };
    return SysOpenFile(&req);
}

static uint32_t create_file(const char* path, uint32_t* handleOut) {
    SYS_PATH_HANDLE_REQUEST req = { SysSvFromCstr(path), handleOut };
    return SysCreateFile(&req);
}

static uint32_t open_dir(const char* path, uint32_t* handleOut) {
    SYS_PATH_HANDLE_REQUEST req = { SysSvFromCstr(path), handleOut };
    return SysOpenDir(&req);
}

static uint32_t set_cwd(const char* path) {
    SYS_PATH_REQUEST req = { SysSvFromCstr(path) };
    return SysSetCwd(&req);
}

static uint32_t delete_file(const char* path) {
    SYS_PATH_REQUEST req = { SysSvFromCstr(path) };
    return SysDeleteFile(&req);
}

static uint32_t create_process(const char* path, uint32_t* handleOut, const char* cmdline) {
    SYS_CREATE_PROCESS_REQUEST req = { SysSvFromCstr(path), SysSvFromCstr(cmdline), handleOut };
    return SysCreateProcess(&req);
}

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); }
}

static void printInt(int32_t n) {
    if (n < 0) { print("-"); printUInt((uint32_t)-(n + 1) + 1); }
    else { printUInt((uint32_t)n); }
}

static void printUInt64(uint64_t n) {
    if (n == 0) { print("0"); return; }
    char buf[20]; int i = 0;
    while (n > 0) { buf[i++] = (char)('0' + (int)(n % 10)); n /= 10; }
    while (i > 0) { char c[2] = { buf[--i], '\0' }; print(c); }
}

// ---------------------------------------------------------------------------
// Line editor
// ---------------------------------------------------------------------------
static void readLine(char* buf, int len) {
    int pos = 0;
    while (true) {
        char c = SysKbReadChar();
        if (!c) { SysYield(); 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';
}

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"
          "  mem               - Show memory usage\n"
          "  ps                - List running process IDs\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");
}

static void printSizeKiB(uint64_t bytes) {
    printUInt64(bytes / 1024u);
    print(" KiB");
}

static void cmd_mem(void) {
    SYS_MEMORY_STATUS st;
    if (SysGetMemoryStatus(&st) != 0) {
        print("mem: failed\n");
        return;
    }

    print("Memory Status:\n");
    print("  Free physical: ");
    printSizeKiB(st.FreePhysicalBytes);
    print("\n  Kernel pool:   ");
    printSizeKiB(st.KernelPoolBytes);
    print("\n  User heap:     ");
    printSizeKiB(st.UserHeapBytes);
    print("\n");
}

static void cmd_ps(void) {
    uint32_t pids[MAX_PIDS];
    size_t count = 0;
    
    uint32_t status = SysGetProcessList(pids, MAX_PIDS, &count);
    if (status != 0) {
        print("ps: failed to retrieve process list\n");
        return;
    }

    print("Running Processes (Count: ");
    printUInt((uint32_t)count);
    print("):\n");
    
    size_t displayCount = count < MAX_PIDS ? count : MAX_PIDS;
    for (size_t i = 0; i < displayCount; i++) {
        print("  PID: ");
        printUInt(pids[i]);
        print("\n");
    }

    if (count > MAX_PIDS) {
        print("  ... and ");
        printUInt((uint32_t)(count - MAX_PIDS));
        print(" more processes.\n");
    }
}

static void cmd_write(const char* args) {
    char filename[MAX_CMD]; int i = 0;
    while (args[i] != ' ' && args[i] != '\0' && i < MAX_CMD - 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; }
    uint32_t hFile;
    if (create_file(filename, &hFile) != 0) { print("write: could not create file\n"); return; }
    size_t written;
    SysWriteFile(hFile, args + i + 1, strlen(args + i + 1), &written);
    SysCloseHandle(hFile);
    print("File written successfully.\n");
}

static void cmd_dir(const char* path) {
    uint32_t hDir;
    const char* target = (path && *path != '\0') ? path : ".";
    
    if (open_dir(target, &hDir) != 0) { 
        print("dir: failed to open directory\n"); 
        return; 
    }

    SYS_DIR_ENTRY ke;
    while (SysReadDir(hDir, &ke) == 0) {
        // Corrected Attribute Check: 0x10 is the Directory bit in FAT
        if (ke.Attr & 0x10) {
            print("<DIR> ");
        } else {
            print("      ");
        }

        print(ke.Name);
        
        // Optional: print file size for non-directories
        if (!(ke.Attr & 0x10)) {
            print(" (");
            printUInt(ke.FileSize);
            print(" bytes)");
        }

        print("\n");
    }
    SysCloseHandle(hDir);
}

static void cmd_type(const char* filename) {
    uint32_t hFile;
    if (open_file(filename, &hFile) != 0) { print("type: cannot open file\n"); return; }
    char buffer[512]; size_t bytesRead;
    while (SysReadFile(hFile, buffer, sizeof(buffer) - 1, &bytesRead) == 0 && bytesRead > 0) {
        buffer[bytesRead] = '\0'; print(buffer);
    }
    SysCloseHandle(hFile); print("\n");
}


static bool extractProgramPath(const char* cmdline, char* out, size_t outSize) {
    if (!cmdline || !out || outSize == 0) return false;

    while (*cmdline == ' ' || *cmdline == '\t') cmdline++;
    if (*cmdline == '\0') return false;

    size_t pos = 0;
    if (*cmdline == '"') {
        cmdline++;
        while (*cmdline && *cmdline != '"' && pos + 1 < outSize)
            out[pos++] = *cmdline++;
    } else {
        while (*cmdline && *cmdline != ' ' && *cmdline != '\t' && pos + 1 < outSize)
            out[pos++] = *cmdline++;
    }

    out[pos] = '\0';
    return pos != 0;
}

// ---------------------------------------------------------------------------
// Run one 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) { SysScreenClear(0); return 0; }
    if (strncmp(cmd, "crash", 5) == 0) {
        // Check the sub-option trailing "crash " (offset 6)
        if (strcmp(cmd + 6, "void") == 0) {
            // Jumping into the void
            void (*invalid_func)(void) = NULL;
            invalid_func();
            return 0;
        }
        else if (strcmp(cmd + 6, "noncanonical") == 0) {
            // Non-canonical pointer dereference
            volatile int *ptr = (volatile int*)0x4242424242424242ULL;
            *ptr = 1337;
            return 0;
        }
        else if (strcmp(cmd + 6, "ud2") == 0) {
            __ud2();
            return 0;
        }
        else if (strcmp(cmd + 6, "nx") == 0) {
            // NX / DEP Violation 
            unsigned char code[] = { 0xC3 }; 
            void (*execute_stack)(void) = (void (*)(void))code;
            execute_stack();
            return 0;
        }
        else if (strcmp(cmd + 6, "divzero") == 0) {
            // Division by zero
            volatile int zero = 0;
            volatile int result = 1 / zero;
            (void)result;
            return 0;
        }
        else {
            // Default fallback if just "crash" or an unknown sub-option is passed
            *(volatile int*)0 = 42;
            return 0;
        }
    }
    if (strcmp(cmd, "mem") == 0) { cmd_mem(); return 0; }
    if (strcmp(cmd, "ps") == 0) { cmd_ps(); 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 (set_cwd(cmd + 3) != 0) print("cd: failed\n"); return 0; }
    if (strncmp(cmd, "del ", 4) == 0) { delete_file(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; }

    char program[MAX_CMD];
    if (!extractProgramPath(cmd, program, sizeof(program))) return 0;

    uint32_t hProc;
    if (create_process(program, &hProc, cmd) == 0) {
        SysWaitForProcess(hProc);
        SysCloseHandle(hProc);
        while (SysKbPoll()) (void)SysKbReadChar();
    } else { print("shell: launch failed\n"); }
    return 0;
}

int main(void) {
    const char* cmdline = SysGetPeb()->CommandLine.Data;
    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");
    SysExitProcess(0);
    return 0;
}