// Copyright (C) 2023, Jakob Wakeling
// All rights reserved.

#include "bltn.h"
#include "exec.h"
#include "parse.h"
#include "util/log.h"
#include "util/util.h"

#include <fcntl.h>
#include <sys/wait.h>
#include <unistd.h>

#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

s32 _ret;

static s32 execute_comm(ast *a, int fdi, int fd[2]);
static s32 execute_pipe(ast *a, int fdi, int fd[2]);

/* Execute a program. */
s32 execute(ast *a, int fdi, int fd[2]) {
	switch (a->k) {
	case AK_COMM: {} return execute_comm(a, fdi, fd);
	case AK_PIPE: {} return execute_pipe(a, fdi, fd);
	default: { log_warn("Unhandled AST kind \"%s\"", ast_ks[a->k]); } return -1;
	}
}

/* Execute a command statement. */
static s32 execute_comm(ast *a, int fdi, int fd[2]) {
	/* If the command is null, then do nothing */
	if (!a->s) { return _ret; }

	/* Handle builtins */
	for (bltn *b = bltns; b->name; b += 1) {
		if (strcmp(a->s, b->name) == 0) {
			return b->fn(a->c.al - 1, a->c.a);
		}
	}

	pid_t pid; int status, rin = -1, rout = -1, rerr = -1;

	/* Open redirect files. */
	if (a->rin.s && (rin = open(a->rin.s, O_RDONLY)) == -1) {
		log_warn("%s: %s", a->rin.s, strerror(errno)); return -1;
	}
	if (a->rout.s && (rout = open(a->rout.s, O_WRONLY | O_CREAT | (a->rout.app ? O_APPEND : O_TRUNC), 0666)) == -1) {
		if (rin != -1) { close(rin); }
		log_warn("%s: %s", a->rout.s, strerror(errno)); return -1;
	}
	if (a->rerr.s && (rerr = open(a->rerr.s, O_WRONLY | O_CREAT | (a->rerr.app ? O_APPEND : O_TRUNC), 0666)) == -1) {
		if (rin != -1) { close(rin); } if (rout != -1) { close(rout); }
		log_warn("%s: %s", a->rerr.s, strerror(errno)); return -1;
	}

	char **av = a->c.a;

	/* Fork and exec the child process */
	if ((pid = fork()) == 0) {
		signal(SIGINT, SIG_DFL);

		if (rin != -1) { dup2(rin, STDIN_FILENO); }
		else { dup2(fdi, STDIN_FILENO); }

		if (rout != -1) { dup2(rout, STDOUT_FILENO); }
		else if (fd) { dup2(fd[1], STDOUT_FILENO); }
		if (fd && fd[0]) { close(fd[0]); }

		if (rerr != -1) { dup2(rerr, STDERR_FILENO); }

		if (execvp((char *)av[0], (char **)av) == -1) {
			if (errno == ENOENT) { log_warn("%s: Command not found", av[0]); }
			else { perror((char *)av[0]); } exit(1);
		}
	}
	else if (pid == -1) { perror((char *)av[0]); }
	else {
		if (rout == -1 && fd) {
			if (fdi != STDIN_FILENO) { close(fdi); } close(fd[1]);
		}
		else {
			if (fd) { close(fd[1]); }
			waitpid(pid, &status, 0);
		}
	}

	if (rin != -1) { close(rin); }
	if (rout != -1) { close(rout); }
	if (rerr != -1) { close(rerr); }

	return WEXITSTATUS(status);
}

static s32 execute_pipe(ast *a, int fdi, int fd[2]) {
	int pd[2]; if (pipe(pd) == -1) { log_warn("PIPE: %s", strerror(errno)); return -1; }
	execute(a->lc, fdi, pd); return execute(a->rc, pd[0], fd);
}