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

#define MAX_CMD 256
#define NAME_MAX 259

typedef struct dirent { char d_name[NAME_MAX + 1]; unsigned char d_type; } dirent;
typedef struct DIR { uint32_t KHandle; dirent Current; bool Valid; } DIR;

extern int read(int fd, void *buf, size_t count);
extern int write(int fd, const void *buf, size_t count);
extern int open(const char *pathname, int flags, ...);
extern int close(int fd);
extern int chdir(const char *path);
extern DIR* opendir(const char* path);
extern dirent* readdir(DIR* d);
extern int closedir(DIR* d);
extern int unlink(const char *pathname);
extern int posix_spawn(int *pid, const char *path, const void *act, const void *attr, char *const argv[], char *const envp[]);
extern int waitpid(int pid, int *status, int options);
extern void exit(int status);
extern void clearscreen(void);
extern void clearkeyboard(void);
extern void PosixFdInit(void);

static int hIn = 0; static int hOut = 1;

static void print(const char* s) { write(hOut, s, strlen(s)); }

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("-"); n = -n; }
    printUInt((uint32_t)n);
}

static void readLine(char* buf, int len) {
    int pos = 0;
    while (true) {
        char c; if (read(hIn, &c, 1) <= 0) break;
        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 int splitCommandLine(char* line, char** argv, int maxArgv) {
    int argc = 0;
    char* p = line;

    while (*p && argc < maxArgv - 1) {
        while (*p == ' ' || *p == '\t') p++;
        if (!*p) break;

        if (*p == '"') {
            p++;
            argv[argc++] = p;
            while (*p && *p != '"') p++;
            if (*p) *p++ = '\0';
        } else {
            argv[argc++] = p;
            while (*p && *p != ' ' && *p != '\t') p++;
            if (*p) *p++ = '\0';
        }
    }

    argv[argc] = NULL;
    return argc;
}

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;
}

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> <txt> - Create a file with text\n"
          "  clear              - Clear the screen\n"
          "  exit               - Close the shell\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; }
    int fd = open(filename, 0x0241, 0644); // O_WRONLY | O_CREAT | O_TRUNC
    if (fd < 0) { print("write: could not create file\n"); return; }
    write(fd, args + i + 1, strlen(args + i + 1));
    close(fd);
    print("File written successfully.\n");
}

static void cmd_dir(const char* path) {
    const char* target = (path && *path != '\0') ? path : ".";
    DIR* d = opendir(target);
    if (!d) { print("dir: cannot access directory\n"); return; }
    dirent* entry;
    while ((entry = readdir(d)) != NULL) {
        if (entry->d_name[0] == '.') continue;
        print(entry->d_type == 1 ? "<DIR> " : "      ");
        print(entry->d_name); print("\n");
    }
    closedir(d);
}

static void cmd_type(const char* filename) {
    int fd = open(filename, 0); // O_RDONLY
    if (fd < 0) { print("type: cannot open file\n"); return; }
    char buffer[512]; int n;
    while ((n = read(fd, buffer, 511)) > 0) { buffer[n] = '\0'; print(buffer); }
    close(fd); print("\n");
}

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) { clearscreen(); 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 (chdir(cmd + 3) != 0) print("cd: failed\n"); return 0; }
    if (strncmp(cmd, "del ", 4) == 0) { unlink(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 cmdBuf[MAX_CMD];
    strncpy(cmdBuf, cmd, MAX_CMD - 1);
    cmdBuf[MAX_CMD - 1] = '\0';

    char* argv[32];
    int argc = splitCommandLine(cmdBuf, argv, 32);
    if (argc == 0) return 0;

    int pid;
    if (posix_spawn(&pid, argv[0], NULL, NULL, argv, NULL) == 0) {
        int status; waitpid(pid, &status, 0);
        clearkeyboard();
    } else { print("shell: launch failed\n"); }
    return 0;
}

int main(void) {
    PosixFdInit();

    const char* cmdline = SysGetCommandLine();
    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");
    exit(0);
}