/* call routing
 *
 * (C) 2020 by Andreas Eversberg <jolly@eversberg.eu>
 * All Rights Reserved
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <signal.h>
#include "../libdebug/debug.h"
#include "call.h"

extern char **environ;

static const char *env_int(const char *name, int value)
{
	char *string = malloc(strlen(name) + 20);

	sprintf(string, "CC_%s=%d", name, value);

	return string;
}

static const char *env_string(const char *name, const char *value)
{
	char *string = malloc(strlen(name) + strlen(value) + 8);

	sprintf(string, "CC_%s=%s", name, value);

	return string;
}

static void enqueue_string(struct string_queue **queue_p, const char *string, const char *suffix)
{
	struct string_queue *queue;

	queue = calloc(1, sizeof(*queue));
	queue->string = malloc(strlen(string) + strlen(suffix) + 1);
	strcpy(queue->string, string);
	strcat(queue->string, suffix);

	while (*queue_p)
		queue_p = &((*queue_p)->next);
	*queue_p = queue;
}

static char *dequeue_string(struct string_queue **queue_p)
{
	struct string_queue *queue = *queue_p;
	char *string;

	if (!queue)
		return NULL;

	string = queue->string;
	*queue_p = queue->next;
	free(queue);

	return string;
}

/* prepare environment with setup info */
void routing_env_msg(routing_t *routing, osmo_cc_msg_t *msg)
{
	uint8_t coding, capability, mode;
	uint8_t type, plan, present, screen, reason;
	uint8_t network_type;
	char number[256], network_id[256];
	int rc, i;

	for (i = 0; environ[i]; i++) {
		routing->envp[routing->envc++] = strdup(environ[i]);
	}

	rc = osmo_cc_get_ie_bearer(msg, 0, &coding, &capability, &mode);
	if (rc >= 0) {
		routing->envp[routing->envc++] = env_int("BEARER_CODING", coding);
		routing->envp[routing->envc++] = env_int("BEARER_CAPABILITY", capability);
		routing->envp[routing->envc++] = env_int("BEARER_MODE", mode);
	}

	rc = osmo_cc_get_ie_calling(msg, 0, &type, &plan, &present, &screen, number, sizeof(number));
	if (rc >= 0) {
		routing->envp[routing->envc++] = env_int("CALLING_TYPE", type);
		routing->envp[routing->envc++] = env_int("CALLING_PLAN", plan);
		routing->envp[routing->envc++] = env_int("CALLING_PRESENT", present);
		routing->envp[routing->envc++] = env_int("CALLING_SCREEN", screen);
		routing->envp[routing->envc++] = env_string("CALLING", number);
	}
	rc = osmo_cc_get_ie_calling_interface(msg, 0, number, sizeof(number));
	if (rc >= 0) {
		routing->envp[routing->envc++] = env_string("CALLING_INTERFACE", number);
	}

	rc = osmo_cc_get_ie_calling(msg, 1, &type, &plan, &present, &screen, number, sizeof(number));
	if (rc >= 0) {
		routing->envp[routing->envc++] = env_int("CALLING2_TYPE", type);
		routing->envp[routing->envc++] = env_int("CALLING2_PLAN", plan);
		routing->envp[routing->envc++] = env_int("CALLING2_PRESENT", present);
		routing->envp[routing->envc++] = env_int("CALLING2_SCREEN", screen);
		routing->envp[routing->envc++] = env_string("CALLING2", number);
	}
	rc = osmo_cc_get_ie_calling_network(msg, 0, &network_type, network_id, sizeof(network_id));
	if (rc >= 0) {
		routing->envp[routing->envc++] = env_string("NETWORK_TYPE", osmo_cc_network_type_name(network_type));
		routing->envp[routing->envc++] = env_string("NETWORK_ID", network_id);
	}
	rc = osmo_cc_get_ie_redir(msg, 0, &type, &plan, &present, &screen, &reason, number, sizeof(number));
	if (rc >= 0) {
		routing->envp[routing->envc++] = env_int("REDIRECTING_TYPE", type);
		routing->envp[routing->envc++] = env_int("REDIRECTING_PLAN", plan);
		routing->envp[routing->envc++] = env_int("REDIRECTING_PRESENT", present);
		routing->envp[routing->envc++] = env_int("REDIRECTING_SCREEN", screen);
		routing->envp[routing->envc++] = env_int("REDIRECTING_REASON", reason);
		routing->envp[routing->envc++] = env_string("REDIRECTING", number);
	}

	rc = osmo_cc_get_ie_called(msg, 0, &type, &plan, number, sizeof(number));
	if (rc >= 0) {
		routing->envp[routing->envc++] = env_int("DIALING_TYPE", type);
		routing->envp[routing->envc++] = env_int("DIALING_PLAN", plan);
	} else
		number[0] = 0;
	/* variable must always be present, so it can be updated when overlap dialing */
	routing->envc_dialing = routing->envc;
	routing->envp[routing->envc++] = env_string("DIALING", number);

	rc = osmo_cc_get_ie_keypad(msg, 0, number, sizeof(number));
	if (rc < 0)
		number[0] = 0;
	/* variable must always be present, so it can be updated when overlap dialing */
	routing->envc_keypad = routing->envc;
	routing->envp[routing->envc++] = env_string("KEYPAD", number);

	rc = osmo_cc_get_ie_complete(msg, 0);
	if (rc >= 0)
		routing->envp[routing->envc++] = env_int("COMPLETE", 1);

	routing->envp[routing->envc++] = NULL;
}

/* update environment with info message */
void routing_env_dialing(routing_t *routing, const char *number, const char *keypad)
{
	free((char *)routing->envp[routing->envc_dialing]);
	routing->envp[routing->envc_dialing] = env_string("DIALING", number);

	free((char *)routing->envp[routing->envc_keypad]);
	routing->envp[routing->envc_keypad] = env_string("KEYPAD", keypad);
}

void routing_env_free(routing_t *routing)
{
	/* remove env */
	while (routing->envc) {
		free((char *)routing->envp[--(routing->envc)]);
		routing->envp[routing->envc] = NULL;
	}
}

/* run script */
void routing_start(routing_t *routing, const char *script, const char *shell)
{
	int in_pipe[2], out_pipe[2], err_pipe[2];
	pid_t pid;
	char x;
	int rc, flags;

	rc = pipe(in_pipe);
	if (rc < 0) {
		epipe:
		PDEBUG(DROUTER, DEBUG_ERROR, "pipe() failed: errno=%d\n", errno);
		abort();
	}
	rc = pipe(out_pipe);
	if (rc < 0)
		goto epipe;
	rc = pipe(err_pipe);
	if (rc < 0)
		goto epipe;

	pid = fork();
	if (pid < 0) {
		PDEBUG(DROUTER, DEBUG_ERROR, "fork() failed: errno=%d\n", errno);
		abort();
	}
	if (pid == 0) {
		const char *argv[] = { shell, "-c", script, NULL };
		struct rlimit rlim;
		int i;

		/* CHILD */
		/* redirect pipes to stdio */
		close(STDIN_FILENO);
		close(STDOUT_FILENO);
		close(STDERR_FILENO);
		dup2(in_pipe[0], STDIN_FILENO);
		dup2(out_pipe[1], STDOUT_FILENO);
		dup2(err_pipe[1], STDERR_FILENO);

		/* close all file descriptors except std* fss */
		getrlimit(RLIMIT_NOFILE, &rlim);
		for (i = 3; i < (int)rlim.rlim_cur; i++)
			close(i);

		/* tell father that we closed all fds */
		putchar('x');
		fflush(stdout);

		/* become script */
		rc = execvpe(argv[0], (char * const*)argv, (char * const*)routing->envp);
		if (rc < 0) {
			printf("error \"%s\"\n", strerror(errno));
		}

		_exit(0);
	}

	/* PARENT */
	PDEBUG(DROUTER, DEBUG_DEBUG, "Running script '%s' as child %d\n", script, pid);

	/* wait for clild to complete closing file descriptors */
	rc = read(out_pipe[0], &x, 1);
	if (rc != 1 || x != 'x') {
		PDEBUG(DROUTER, DEBUG_ERROR, "communication with child failed!\n");
		kill(pid, SIGKILL);
		abort();
	}

	/* close unused file descriptors, except the child's side
	 * this is because we need to keep it open to get all data from stdout/stderr
	 * after the child exitted. for some reason the pipe is flused on close.
	 */
	close(in_pipe[0]);

	/* make nonblocking IO */
	flags = fcntl(in_pipe[1], F_GETFL);
	flags |= O_NONBLOCK;
	fcntl(in_pipe[1], F_SETFL, flags);
	flags = fcntl(out_pipe[0], F_GETFL);
	flags |= O_NONBLOCK;
	fcntl(out_pipe[0], F_SETFL, flags);
	flags = fcntl(err_pipe[0], F_GETFL);
	flags |= O_NONBLOCK;
	fcntl(err_pipe[0], F_SETFL, flags);

	/* attach pipes and pid to routing */
	routing->script_pid = pid;
	routing->script_stdin = in_pipe[1];
	routing->script_stdout = out_pipe[0];
	routing->script_stdout_child = out_pipe[1];
	routing->script_stderr = err_pipe[0];
	routing->script_stderr_child = err_pipe[1];

	routing->routing = 1;

	PDEBUG(DROUTER, DEBUG_DEBUG, "Routing script started.\n");
}


void routing_stop(routing_t *routing)
{
	char *string;

	/* kill or at least try to */
	if (routing->script_pid) {
		kill(routing->script_pid, SIGTERM);
		routing->script_pid = 0;
	}

	/* close files towards script */
	if (routing->script_stdin) {
		close(routing->script_stdin);
		routing->script_stdin = 0;
	}
	if (routing->script_stdout) {
		close(routing->script_stdout);
		routing->script_stdout = 0;
		close(routing->script_stdout_child);
		routing->script_stdout_child = 0;
	}
	if (routing->script_stderr) {
		close(routing->script_stderr);
		routing->script_stderr = 0;
		close(routing->script_stderr_child);
		routing->script_stderr_child = 0;
	}

	/* flush queues */
	while (routing->stdin_queue) {
		string = dequeue_string(&routing->stdin_queue);
		free(string);
	}
	while (routing->stdout_queue) {
		string = dequeue_string(&routing->stdout_queue);
		free(string);
	}
	routing->stdout_pos = 0;
	while (routing->stderr_queue) {
		string = dequeue_string(&routing->stderr_queue);
		free(string);
	}
	routing->stderr_pos = 0;

	routing->routing = 0;

	PDEBUG(DROUTER, DEBUG_DEBUG, "Routing script stopped.\n");
}


void routing_send(routing_t *routing, const char *string)
{
	PDEBUG(DROUTER, DEBUG_DEBUG, "Sending line to routing script: '%s'\n", string);
	enqueue_string(&routing->stdin_queue, string, "\n");
}

static int routing_handle_stdin(routing_t *routing)
{
	char *string;
	int rc;

	/* write to script */
	if (routing->stdin_queue && routing->script_stdin) {
		rc = write(routing->script_stdin, routing->stdin_queue->string, strlen(routing->stdin_queue->string));
		if (rc < 0) {
			if (errno == EAGAIN)
				return -EAGAIN;
		}
		if (rc <= 0) {
			close(routing->script_stdin);
			routing->script_stdin = 0;
			return 0;
		}
		string = dequeue_string(&routing->stdin_queue);
		free(string);
		return 0;
	}

	return -EINVAL;
}

static int routing_handle_stdout(routing_t *routing)
{
	int rc, i;

	/* read from script */
	if (routing->script_stdout) {
		rc = read(routing->script_stdout, routing->stdout_buffer + routing->stdout_pos, sizeof(routing->stdout_buffer) - routing->stdout_pos);
		if (rc < 0) {
			if (errno == EAGAIN) {
				/* if script has terminated (pid is set to 0) and stdout/stderr queue is empty */
				if (!routing->script_pid && !routing->stdout_queue && !routing->stderr_queue) {
					routing_stop(routing);
					routing_close(routing);
					return 0;
				}
				return -EAGAIN;
			}
		}
		if (rc <= 0) {
			close(routing->script_stdout);
			routing->script_stdout = 0;
			return 0;
		}
		routing->stdout_pos += rc;
		i = 0;
		while (i < routing->stdout_pos) {
			if (routing->stdout_buffer[i] != '\n') {
				i++;
				continue;
			}
			routing->stdout_buffer[i] = '\0';
			enqueue_string(&routing->stdout_queue, routing->stdout_buffer, "");
			i++;
			if (i < routing->stdout_pos)
				memcpy(routing->stdout_buffer, routing->stdout_buffer + i, routing->stdout_pos - i);
			routing->stdout_pos -= i;
			i = 0;
		}
		if (i == sizeof(routing->stdout_buffer)) {
			PDEBUG(DROUTER, DEBUG_ERROR, "Output line from script too long, please fix!\n");
			routing->stdout_pos = 0;
		}
		return 0;
	}

	return -EINVAL;
}

static int routing_handle_stderr(routing_t *routing)
{
	int rc, i;

	/* read from script */
	if (routing->script_stderr) {
		rc = read(routing->script_stderr, routing->stderr_buffer + routing->stderr_pos, sizeof(routing->stderr_buffer) - routing->stderr_pos);
		if (rc < 0) {
			if (errno == EAGAIN) {
				/* if script has terminated (pid is set to 0) and stdout/stderr queue is empty */
				if (!routing->script_pid && !routing->stdout_queue && !routing->stderr_queue) {
					routing_stop(routing);
					routing_close(routing);
					return 0;
				}
				return -EAGAIN;
			}
		}
		if (rc <= 0) {
			close(routing->script_stderr);
			routing->script_stderr = 0;
			return 0;
		}
		routing->stderr_pos += rc;
		i = 0;
		while (i < routing->stderr_pos) {
			if (routing->stderr_buffer[i] != '\n') {
				i++;
				continue;
			}
			routing->stderr_buffer[i] = '\0';
			enqueue_string(&routing->stderr_queue, routing->stderr_buffer, "");
			i++;
			if (i < routing->stderr_pos)
				memcpy(routing->stderr_buffer, routing->stderr_buffer + i, routing->stderr_pos - i);
			routing->stderr_pos -= i;
			i = 0;
		}
		if (i == sizeof(routing->stderr_buffer)) {
			PDEBUG(DROUTER, DEBUG_ERROR, "Output line from script too long, please fix!\n");
			routing->stderr_pos = 0;
		}
		return 0;
	}

	return -EINVAL;
}

/* handle everything that has to do with routing
 * note that work may cause the call to be destroyed
 */
int routing_handle(routing_t *routing)
{
	char *string;
	int rc;

	rc = routing_handle_stdin(routing);
	if (rc == 0)
		return 1;
	rc = routing_handle_stdout(routing);
	if (rc == 0)
		return 1;
	rc = routing_handle_stderr(routing);
	if (rc == 0)
		return 1;

	if (routing->stdout_queue) {
		string = dequeue_string(&routing->stdout_queue);
		PDEBUG(DROUTER, DEBUG_DEBUG, "Routing script returned line from stdout: '%s'\n", string);
		routing_receive_stdout(routing, string);
		free(string);
		return 1;
	}
	if (routing->stderr_queue) {
		string = dequeue_string(&routing->stderr_queue);
		routing_receive_stderr(routing, string);
		free(string);
		return 1;
	}

	return 0;
}

#warning achja: beim router darf rtp-proxy und call nur erfolgen, wenn noch kein codec negoitiated wurde. call darf aber nach call erfolgen, wenn rtp-proxy verwendet wird. tones und record darf erfolgen wemm rtp-proxy verwendet wird