/*
 * menunix_clone.c
 *
 * A simple Menunix-style menu interface for UNIX-like systems (terminal).
 *
 * Build:
 *   gcc -o menunix_clone menunix_clone.c
 *
 * Run:
 *   ./menunix_clone
 *
 * Notes:
 *  - Uses system() to run shell commands (simple and portable).
 *  - Uses $EDITOR environment variable for text editing (falls back to vi/nano).
 *  - Designed as a small demo; not production security-hardened.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define LINEBUF 512

/* Utility to read a line of input */
static void read_line(char *buf, size_t n) {
    if (!fgets(buf, n, stdin)) {
        buf[0] = '\0';
        return;
    }
    /* strip newline */
    size_t len = strlen(buf);
    if (len && buf[len-1] == '\n') buf[len-1] = '\0';
}

/* Wait for Enter */
static void wait_return(void) {
    printf("\nPress <RETURN> to continue...");
    fflush(stdout);
    char tmp[8];
    read_line(tmp, sizeof(tmp));
}

/* Run a shell command and display output (system() shows output directly) */
static int run_command(const char *cmd) {
    if (!cmd || !cmd[0]) return -1;
    int rc = system(cmd);
    return rc;
}

/* File operations submenu */
static void menu_file_ops(void) {
    char choice[16], arg[LINEBUF], cmd[LINEBUF];

    for (;;) {
        printf("\n----- File Operations -----\n\n");
        printf(" 1. List files in current directory\n");
        printf(" 2. Copy a file\n");
        printf(" 3. Move or rename a file\n");
        printf(" 4. Delete a file\n");
        printf(" 5. Change directory\n");
        printf(" 6. Show current directory\n");
        printf(" 7. Return to Main Menu\n\n");
        printf("Enter choice (1-7): ");
        read_line(choice, sizeof(choice));
        if (!strcmp(choice, "1")) {
            printf("\nExecuting: ls -l\n\n");
            run_command("ls -l");
            wait_return();
        } else if (!strcmp(choice, "2")) {
            printf("Source file: ");
            read_line(arg, sizeof(arg));
            if (!arg[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            printf("Destination: ");
            char dest[LINEBUF];
            read_line(dest, sizeof(dest));
            if (!dest[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            snprintf(cmd, sizeof(cmd), "cp -i -- '%s' '%s'", arg, dest);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "3")) {
            printf("Source (or current name): ");
            read_line(arg, sizeof(arg));
            if (!arg[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            char dest[LINEBUF];
            printf("Destination (new name): ");
            read_line(dest, sizeof(dest));
            if (!dest[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            snprintf(cmd, sizeof(cmd), "mv -i -- '%s' '%s'", arg, dest);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "4")) {
            printf("File to delete: ");
            read_line(arg, sizeof(arg));
            if (!arg[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            snprintf(cmd, sizeof(cmd), "rm -i -- '%s'", arg);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "5")) {
            printf("Change directory to: ");
            read_line(arg, sizeof(arg));
            if (!arg[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            if (chdir(arg) == 0) {
                printf("Directory changed to: ");
                run_command("pwd");
            } else {
                perror("chdir");
            }
            wait_return();
        } else if (!strcmp(choice, "6")) {
            run_command("pwd");
            wait_return();
        } else if (!strcmp(choice, "7") || choice[0] == '\0') {
            break;
        } else {
            printf("Invalid choice.\n");
        }
    }
}

/* Text editing submenu */
static void menu_text_editing(void) {
    char choice[16], filename[LINEBUF], cmd[LINEBUF];
    for (;;) {
        printf("\n----- Text Editing -----\n\n");
        printf(" 1. Edit file (open in $EDITOR)\n");
        printf(" 2. View file (pager)\n");
        printf(" 3. Return to Main Menu\n\n");
        printf("Enter choice (1-3): ");
        read_line(choice, sizeof(choice));
        if (!strcmp(choice, "1")) {
            printf("Filename to edit: ");
            read_line(filename, sizeof(filename));
            if (!filename[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            const char *editor = getenv("EDITOR");
            if (!editor || !editor[0]) editor = "vi";
            snprintf(cmd, sizeof(cmd), "%s '%s'", editor, filename);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "2")) {
            printf("Filename to view: ");
            read_line(filename, sizeof(filename));
            if (!filename[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            const char *pager = getenv("PAGER");
            if (!pager || !pager[0]) pager = "less";
            snprintf(cmd, sizeof(cmd), "%s '%s'", pager, filename);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "3") || choice[0] == '\0') {
            break;
        } else {
            printf("Invalid choice.\n");
        }
    }
}

/* Printing submenu */
static void menu_printing(void) {
    char choice[16], filename[LINEBUF], cmd[LINEBUF];
    for (;;) {
        printf("\n----- Printing -----\n\n");
        printf(" 1. Print a file (lpr or lp)\n");
        printf(" 2. List print queue (lpstat/lpq)\n");
        printf(" 3. Return to Main Menu\n\n");
        printf("Enter choice (1-3): ");
        read_line(choice, sizeof(choice));
        if (!strcmp(choice, "1")) {
            printf("Filename to print: ");
            read_line(filename, sizeof(filename));
            if (!filename[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            /* try lpr then lp */
            if (access("/usr/bin/lpr", X_OK) == 0 || access("/bin/lpr", X_OK) == 0) {
                snprintf(cmd, sizeof(cmd), "lpr '%s'", filename);
            } else {
                snprintf(cmd, sizeof(cmd), "lp '%s'", filename);
            }
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "2")) {
            if (access("/usr/bin/lpq", X_OK) == 0 || access("/bin/lpq", X_OK) == 0) {
                run_command("lpq");
            } else {
                run_command("lpstat -o");
            }
            wait_return();
        } else if (!strcmp(choice, "3") || choice[0] == '\0') {
            break;
        } else {
            printf("Invalid choice.\n");
        }
    }
}

/* Compile and Run submenu */
static void menu_compile_run(void) {
    char choice[16], filename[LINEBUF], cmd[LINEBUF], outname[LINEBUF];
    for (;;) {
        printf("\n----- Compile and Run Programs -----\n\n");
        printf(" 1. Compile C program\n");
        printf(" 2. Run executable\n");
        printf(" 3. Compile and run in one step\n");
        printf(" 4. Return to Main Menu\n\n");
        printf("Enter choice (1-4): ");
        read_line(choice, sizeof(choice));
        if (!strcmp(choice, "1")) {
            printf("Source filename (e.g., prog.c): ");
            read_line(filename, sizeof(filename));
            if (!filename[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            printf("Output executable name (or blank for 'a.out'): ");
            read_line(outname, sizeof(outname));
            if (!outname[0]) strcpy(outname, "a.out");
            snprintf(cmd, sizeof(cmd), "cc -Wall -o '%s' '%s'", outname, filename);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "2")) {
            printf("Executable name (path): ");
            read_line(filename, sizeof(filename));
            if (!filename[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            snprintf(cmd, sizeof(cmd), "'%s'", filename);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "3")) {
            printf("Source filename (e.g., prog.c): ");
            read_line(filename, sizeof(filename));
            if (!filename[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            printf("Output executable name (or blank for 'a.out'): ");
            read_line(outname, sizeof(outname));
            if (!outname[0]) strcpy(outname, "a.out");
            snprintf(cmd, sizeof(cmd), "cc -Wall -o '%s' '%s' && './%s'", outname, filename, outname);
            run_command(cmd);
            wait_return();
        } else if (!strcmp(choice, "4") || choice[0] == '\0') {
            break;
        } else {
            printf("Invalid choice.\n");
        }
    }
}

/* Mail and messaging submenu */
static void menu_mail(void) {
    char choice[16], cmd[LINEBUF], to[LINEBUF], subj[LINEBUF], bodyfile[LINEBUF];
    for (;;) {
        printf("\n----- Mail and Messaging -----\n\n");
        printf(" 1. Send a simple mail\n");
        printf(" 2. Check mail (mailx/mail)\n");
        printf(" 3. Return to Main Menu\n\n");
        printf("Enter choice (1-3): ");
        read_line(choice, sizeof(choice));
        if (!strcmp(choice, "1")) {
            printf("To (username@host): ");
            read_line(to, sizeof(to));
            if (!to[0]) { printf("Cancelled.\n"); wait_return(); continue; }
            printf("Subject: ");
            read_line(subj, sizeof(subj));
            printf("Enter message body filename (temporary file): ");
            read_line(bodyfile, sizeof(bodyfile));
            if (!bodyfile[0]) {
                /* if no file provided, create a temp with input until EOF */
                char tmpname[] = "/tmp/menunix_msg_XXXXXX";
                int fd = mkstemp(tmpname);
                if (fd == -1) {
                    perror("mkstemp");
                    wait_return();
                    continue;
                }
                printf("Enter message. End with a single line containing only a dot '.'\n");
                FILE *tf = fdopen(fd, "w");
                if (!tf) { perror("fdopen"); close(fd); wait_return(); continue; }
                char line[LINEBUF];
                for (;;) {
                    read_line(line, sizeof(line));
                    if (!strcmp(line, ".")) break;
                    fprintf(tf, "%s\n", line);
                }
                fclose(tf);
                snprintf(cmd, sizeof(cmd), "cat '%s' | mail -s '%s' %s", tmpname, subj, to);
                run_command(cmd);
                snprintf(cmd, sizeof(cmd), "rm -f '%s'", tmpname);
                run_command(cmd);
            } else {
                snprintf(cmd, sizeof(cmd), "cat '%s' | mail -s '%s' %s", bodyfile, subj, to);
                run_command(cmd);
            }
            wait_return();
        } else if (!strcmp(choice, "2")) {
            if (access("/usr/bin/mail", X_OK) == 0 || access("/bin/mail", X_OK) == 0) {
                run_command("mail");
            } else if (access("/usr/bin/mailx", X_OK) == 0 || access("/bin/mailx", X_OK) == 0) {
                run_command("mailx");
            } else {
                printf("No 'mail' client found on PATH.\n");
            }
            wait_return();
        } else if (!strcmp(choice, "3") || choice[0] == '\0') {
            break;
        } else {
            printf("Invalid choice.\n");
        }
    }
}

/* System information submenu */
static void menu_system_info(void) {
    char choice[16];
    for (;;) {
        printf("\n----- System Information -----\n\n");
        printf(" 1. Show uname (system name)\n");
        printf(" 2. Show uptime\n");
        printf(" 3. Show disk usage (df -h)\n");
        printf(" 4. Show memory (free or vmstat)\n");
        printf(" 5. Return to Main Menu\n\n");
        printf("Enter choice (1-5): ");
        read_line(choice, sizeof(choice));
        if (!strcmp(choice, "1")) {
            run_command("uname -a");
            wait_return();
        } else if (!strcmp(choice, "2")) {
            run_command("uptime");
            wait_return();
        } else if (!strcmp(choice, "3")) {
            run_command("df -h");
            wait_return();
        } else if (!strcmp(choice, "4")) {
            if (access("/usr/bin/free", X_OK) == 0 || access("/bin/free", X_OK) == 0) {
                run_command("free -h");
            } else {
                run_command("vmstat -s");
            }
            wait_return();
        } else if (!strcmp(choice, "5") || choice[0] == '\0') {
            break;
        } else {
            printf("Invalid choice.\n");
        }
    }
}

/* Change password (calls passwd) */
static void menu_change_password(void) {
    printf("\n----- Change Password -----\n\n");
    if (access("/usr/bin/passwd", X_OK) == 0 || access("/bin/passwd", X_OK) == 0) {
        run_command("passwd");
    } else {
        printf("'passwd' not found on this system.\n");
    }
    wait_return();
}

/* Main */
int main(int argc, char *argv[]) {
    char choice[16];

    /* Greeting */
    char *user = getenv("USER");
    if (!user) user = getenv("LOGNAME");
    if (!user) user = "user";

    printf("**********************************************\n");
    printf("*             M  E  N  U  N  I  X            *\n");
    printf("*     A Menu Interface for the UNIX System   *\n");
    printf("**********************************************\n\n");
    printf("Welcome to Menunix (clone), user: %s\n\n", user);

    for (;;) {
        printf("\nPlease choose from the following:\n\n");
        printf(" 1. File Operations\n");
        printf(" 2. Text Editing\n");
        printf(" 3. Printing\n");
        printf(" 4. Compile and Run Programs\n");
        printf(" 5. Mail and Messaging\n");
        printf(" 6. System Information\n");
        printf(" 7. Change Password\n");
        printf(" 8. Exit to UNIX shell\n\n");
        printf("Enter choice (1-8): ");
        read_line(choice, sizeof(choice));
        if (!strcmp(choice, "1")) {
            menu_file_ops();
        } else if (!strcmp(choice, "2")) {
            menu_text_editing();
        } else if (!strcmp(choice, "3")) {
            menu_printing();
        } else if (!strcmp(choice, "4")) {
            menu_compile_run();
        } else if (!strcmp(choice, "5")) {
            menu_mail();
        } else if (!strcmp(choice, "6")) {
            menu_system_info();
        } else if (!strcmp(choice, "7")) {
            menu_change_password();
        } else if (!strcmp(choice, "8")) {
            printf("\nExiting Menunix... returning to UNIX shell.\n\n");
            break;
        } else if (choice[0] == '\0') {
            /* treat Enter as redisplay */
            continue;
        } else {
            printf("Invalid choice.\n");
        }
    }

    /* Hand control back to user's shell */
    printf("$ ");
    fflush(stdout);
    /* Exec a shell (respect SHELL env var) */
    const char *shell = getenv("SHELL");
    if (!shell) shell = "/bin/sh";
    execlp(shell, shell, (char *)NULL);
    /* If execlp fails, fall back to exit */
    perror("execlp");
    return 0;
}