#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>

#include "nfcommander.h"
#include "command.h"
#include "config.h"
#include "reader.h"

#define COMMAND_ALIVE 1
#define COMMAND_STOPPED 2

#define INPUT_BUFFER_MAX 2048

typedef struct {
	uint8_t flags;
	pid_t child;
	int iopipe[2];
	nfc_tag_info_t* tag;

	size_t input_head;
	uint8_t input[INPUT_BUFFER_MAX];
} command_t;

static size_t ncommands = 0;
static command_t* commands = NULL;

//TODO timeouting / SIGKILL

static int command_scan_input(command_t* cmd, size_t bytes){
	size_t n = 0;

	//check for line ending
	for(n = 0; n < bytes; n++){
		if(cmd->input[cmd->input_head + n] == '\r' || 
				cmd->input[cmd->input_head + n] == '\n'){
			//terminate string
			cmd->input[cmd->input_head + n] = 0;
			//handle line
			if(!strncmp((char*) cmd->input, "UPDATE ", strlen("UPDATE "))){
				if(cmd->tag && strlen((char*) (cmd->input + 7)) < cmd->tag->dynamic_max){
					free(cmd->tag->dynamic_data);
					cmd->tag->dynamic_data = (uint8_t*) strdup((char*) (cmd->input + 7));
					cmd->tag->dynamic_length = strlen((char*) cmd->tag->dynamic_data);
					reader_write(cmd->tag, TAG_WRITE_DYNAMIC);
				}
				else{
					printf("Failed to update tag dynamic data\n");
				}
			}

			//find beginning of next line
			n++;
			for(; n < bytes && !isprint(cmd->input[cmd->input_head + n]); n++){
			}

			if(n == bytes){
				cmd->input_head = 0;
				return 0;
			}

			//move back
			memmove(cmd->input, cmd->input + cmd->input_head + n, bytes - n);
			cmd->input_head = 0;

			//try to find another sentence
			return command_scan_input(cmd, bytes - n);
		}
		else if(!isprint(cmd->input[cmd->input_head + n])){
			cmd->input[cmd->input_head + n] = ' ';
		}
	}

	if(cmd->input_head + bytes > INPUT_BUFFER_MAX - 10){
		//line too long - ignore it entirely until the next linebreak
		cmd->input_head = 1;
		cmd->input[0] = 0; //fail any test for UPDATE
		return 0;
	}

	//no newline
	cmd->input_head += bytes;
	return 0;
}

int command_handle(int fd){
	size_t n = 0;
	ssize_t bytes;

	//find matching command
	for(n = 0; n < ncommands; n++){
		if(commands[n].flags & COMMAND_ALIVE
				&& fd == commands[n].iopipe[0]){
			bytes = read(fd, commands[n].input + commands[n].input_head,
					sizeof(commands[n].input) - commands[n].input_head - 1);
			if(bytes < 0){
				perror("cmd/recv");
			}
			else if(bytes == 0){
				printf("Command %lu pipe closed\n", n);
				core_manage_fd(commands[n].iopipe[0], 0, system_command);
				close(commands[n].iopipe[0]);
				commands[n].iopipe[0] = -1;
				commands[n].input_head = 0;
			}
			else{
				//printf("%ld bytes from command %lu\n", bytes, n);
				command_scan_input(commands + n, bytes);
			}
			return 0;
		}
	}

	printf("Unhandled command fd\n");
	return 1;
}

void command_reap(){
	int wait_status;
	pid_t status;
	size_t n;

	do {
		status = waitpid(-1, &wait_status, WNOHANG);
		if(status < 0 && errno != ECHILD){
			perror("cmd/reap");
		}
		if(status <= 0){
			return;
		}

		//find matching command
		if(status){
			for(n = 0; n < ncommands; n++){
				if(commands[n].child == status){
					commands[n].flags = 0;
					commands[n].child = -1;
					if(commands[n].iopipe[0] >= 0){
						core_manage_fd(commands[n].iopipe[0], 0, system_command);
						close(commands[n].iopipe[0]);
						commands[n].iopipe[0] = -1;
					}
					printf("Command %lu terminated\n", n);
				}
			}
		}
	} while(status);
}

static int command_spawn(command_t* cmd, char* command_name, char* command_static){
	char* workdir = config_get("command", "chdir");
	char* handler = config_get("command", "handler");
	char tag_uid[12] = "", dynsize[10] = "";
	size_t bytes;
	char* dynamic = (cmd->tag->dynamic_length) ? calloc(cmd->tag->dynamic_length + 1, sizeof(uint8_t)) : NULL;

	printf("Starting command %s, static %s\n", command_name, command_static);
	if(pipe(cmd->iopipe)){
		perror("cmd/pipe");
		return 1;
	}

	if(fcntl(cmd->iopipe[0], F_SETFD, FD_CLOEXEC)){
		perror("cmd/fcntl");
	}

	cmd->child = fork();
	switch(cmd->child){
		case -1:
			perror("cmd/fork");
			return 1;
		case 0:
			//child
			if(workdir && chdir(workdir)){
				perror("child/chdir");
				_exit(1);
			}

			//make child a session leader
			setpgrp();

			//connect stdout
			while((dup2(cmd->iopipe[1], STDOUT_FILENO) == -1) && (errno == EINTR)) {
			}
			close(cmd->iopipe[1]);

			//set environment
			bytes = snprintf(tag_uid, sizeof(tag_uid), "%02X%02X%02X%02X",
					cmd->tag->uid[0], cmd->tag->uid[1],
					cmd->tag->uid[2], cmd->tag->uid[3]);
			if(cmd->tag->uid_length > 4){
				bytes += snprintf(tag_uid + bytes, sizeof(tag_uid) - bytes, "%02X%02X%02X",
						cmd->tag->uid[4], cmd->tag->uid[5],
						cmd->tag->uid[6]);
			}
			snprintf(dynsize, sizeof(dynsize), "%ld", cmd->tag->dynamic_max);
			setenv("TAG_UID", tag_uid, 1);
			setenv("MAX_DATA_LENGTH", dynsize, 1);

			if(dynamic){
				memcpy(dynamic, cmd->tag->dynamic_data, cmd->tag->dynamic_length);
			}

			//run actual command
			if(handler){
				execl(handler, handler, command_name, command_static, dynamic, NULL);
			}
			else{
				execl(command_name, command_name, command_static, dynamic, NULL);
			}
			perror("child/exec");
			_exit(1);
		default:
			//parent
			cmd->flags |= COMMAND_ALIVE;
			close(cmd->iopipe[1]);
			core_manage_fd(cmd->iopipe[0], 1, system_command);
	}

	return 0;
}

int command_start(nfc_tag_info_t* info){
	size_t n = 0, p = ncommands;
	uint8_t* command_name = NULL, *command_static = NULL;

	for(n = 0; n < ncommands; n++){
		//if command already in list, do nothing
		if(commands[n].tag == info){
			//this should not normally happen
			return 0;
		}

		//mark available slot
		if(!commands[n].tag && !commands[n].flags){
			p = n;
		}
	}

	//cant run without an actual command
	if(!info->static_data || !info->static_length){
		printf("Tag contains no command data\n");
		return 0;
	}

	//parse out command data
	command_name = calloc(info->static_length + 1, sizeof(uint8_t));
	if(!command_name){
		printf("Failed to allocate memory\n");
		return 1;
	}
	memcpy(command_name, info->static_data, info->static_length);
	for(n = 0; n < info->static_length; n++){
		if(!isalnum(command_name[n])){
			command_name[n] = 0;
			if(info->static_length - n > 1){
				command_static = command_name + n + 1;
			}
			break;
		}
	}

	if(!strlen((char*) command_name)){
		printf("Tag contains invalid command data\n");
		free(command_name);
		return 1;
	}

	if(p == ncommands){
		commands = realloc(commands, (p + 1) * sizeof(command_t));
		if(!commands){
			ncommands = 0;
			printf("Failed to allocate memory\n");
			free(command_name);
			return 1;
		}
		memset(commands + p, 0, sizeof(command_t));
		ncommands++;
	}

	commands[p].tag = info;
	commands[p].input_head = 0;
	if(command_spawn(commands + p, (char*) command_name, (char*) command_static)){
		//TODO clean up and free command instance
	}

	free(command_name);
	return 0;
}

static void command_stop_internal(size_t n){
	//send SIGTERM to process group
	if(kill(-commands[n].child, (commands[n].flags & COMMAND_STOPPED) ? SIGKILL : SIGTERM)){
		perror("cmd/stop");
	}
	commands[n].flags |= COMMAND_STOPPED;
}

int command_stop(nfc_tag_info_t* info){
	size_t n = 0;

	for(n = 0; n < ncommands; n++){
		if(commands[n].tag == info){
			commands[n].tag = NULL;
			if(commands[n].flags & COMMAND_ALIVE){
				command_stop_internal(n);
			}
		}
	}

	return 0;
}

void command_free(){
	size_t n = 0;

	printf("Shutting down any remaining commands\n");
	for(n = 0; n < ncommands; n++){
		while(commands[n].flags & COMMAND_ALIVE){
			command_stop_internal(n);
			command_reap();
		}
	}

	ncommands = 0;
	free(commands);
	commands = NULL;
}