/* noshmore
 * an extended version of nosh,
 * the minimal POSIX C shell.
 * -> generally: adds some functionality.
 *
 * von czjstmax, <jstmaxlol at disroot dot org>
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <stdbool.h>
#include <wordexp.h>
#include <sys/wait.h>
#include <readline/readline.h>
#include <readline/history.h>

#define NOSHMORE_VERSION    2
#define MAX_ALIASES         256

typedef struct {
    char *dst;
    char *src;
} Alias;

Alias aliases[MAX_ALIASES];
int alias_count = 0;

void handlecc(int sig);
Alias CreateAlias(char *dst, char *src);
void FreeAll();
void FreeAliases();

char *line = NULL;
wordexp_t p;

int main(void)
{
    signal(SIGINT, handlecc);
    char *USER = getenv("USER");
    if (!USER)
        USER = "anon";
    char *HOME = getenv("HOME");
    if (!HOME)
        HOME = ".";

    while (true) {
        char prompt[strlen(USER) + strlen("$ ") + 1];
        snprintf(prompt, sizeof(prompt), "%s$ ", USER);

        line = readline(prompt);

        if (!line)
            break;
        if (*line)
            add_history(line);

        if (wordexp(line, &p, 0) != 0) {
            fprintf(stderr, "nsh+! ERROR while parsing\n");
            free(line);
            continue;
        }

        // built-ins
        if (p.we_wordc == 0) {
            FreeAll();
            continue;
        }
        if (strcmp(p.we_wordv[0], ":q") == 0 || strcmp(p.we_wordv[0], "exit") == 0) {
            FreeAll();
            FreeAliases();
            return 0;
        }
        else if (strcmp(p.we_wordv[0], "echo") == 0) {
            for (size_t i = 1; i < p.we_wordc; i++)
                printf("%s ", p.we_wordv[i]);
            if (p.we_wordc >= 2) {
                if (strcmp(p.we_wordv[1], "-c") != 0)
                    printf("\n");
                else continue;
            }
        }
        else if (strcmp(p.we_wordv[0], "alias") == 0) {
            if (p.we_wordc <= 2) {
                fprintf(stderr, "nsh+! ERROR: expected 2 args\n");
            } else {
                // overwrite if exists
                bool found = false;
                for (int i = 0; i < alias_count; i++) {
                    if (strcmp(aliases[i].dst, p.we_wordv[1]) == 0) {
                        free(aliases[i].src);
                        aliases[i].src = strdup(p.we_wordv[2]);
                        found = true;
                        break;
                    }
                }

                if (!found && alias_count < MAX_ALIASES) {
                    aliases[alias_count++] = CreateAlias(p.we_wordv[1], p.we_wordv[2]);
                }
            }
        }
        else if (strcmp(p.we_wordv[0], "cd") == 0) {
            if (p.we_wordc <= 1) {
                if (chdir(HOME))
                    perror("nsh+! ERROR: cannot retrieve HOME, failed to change directory");
                FreeAll();
                continue;
            }
            if (chdir(p.we_wordv[1]))
                perror("nsh+! ERROR: failed to change directory");
        }
        else if (strcmp(p.we_wordv[0], "clear") == 0) {
            printf("\033[2J\033[H\033[3J");
            fflush(stdout);
        }
        else if (strcmp(p.we_wordv[0], "help") == 0) {
            printf(
                "noshmore\tVERSION(%d)\tALIASES(%d)\n"
                "an extended version of nosh, the minimal POSIX C shell.\n"
                "\n"
                "built-ins:\n"
                "echo  -> outputs a string of text, doesn't need \" enclosure.\n"
                "         supports '-c' for output without '\\n'"
                "clear -> clears screen (and scrollback)\n"
                "alias -> creates non-persistent command aliases\n"
                "         (i.e. alias v vim)\n"
                "cd    -> change working directory\n"
                "help  -> prints this screen\n"
                "\ngithub repo: github.com/jstmaxlol/noshmore\n"
                , NOSHMORE_VERSION, MAX_ALIASES
            );
        }
        else {
            for (int i = 0; i < alias_count; i++) {
                if (strcmp(p.we_wordv[0], aliases[i].dst) == 0) {
                    char new_line[81920] = {0};
                    strcat(new_line, aliases[i].src);

                    for (size_t j = 1; j < p.we_wordc; j++) {
                        strcat(new_line, " ");
                        strcat(new_line, p.we_wordv[j]);
                    }

                    wordfree(&p);
                    if (wordexp(new_line, &p, 0) != 0) {
                        fprintf(stderr, "nsh+! ERROR: alias expansion failed\n");
                        break;
                    }

                    break;
                }
            }
            pid_t pid = fork();
            char **argv = p.we_wordv; // pray with me now
            if (pid == 0) {
                execvp(p.we_wordv[0], argv);
                perror("nsh+! ERROR: failed to execvp()");
                FreeAll();
                _exit(1);
            }
            else if (pid > 0) {
                int status;
                waitpid(pid, &status, 0);
            }
            else {
                fprintf(stderr, "nsh+! ERROR: %s not found\n", p.we_wordv[0]);
            }
        }
    }
}

void handlecc(int sig)
{
    (void)sig;
    rl_replace_line("", 0);
    printf("\n");
    rl_on_new_line();
    rl_redisplay();
}

Alias CreateAlias(char *dst, char *src)
{
    Alias alias;
    alias.dst = strdup(dst);
    alias.src = strdup(src);
    return alias;
}

void FreeAll()
{
    wordfree(&p);
    free(line);
    line = NULL;
}

void FreeAliases()
{
    for (int i = 0; i < alias_count; i++) {
        free(aliases[i].dst);
        free(aliases[i].src);
    }

}