#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <time.h>
#include <sys/types.h>

#define PROMPT "msh> "
#define EXIT_CMD "exit"
#define MAX_BUF 121

// Statuses from builtin responses
#define RESP_HELP 1
#define RESP_DATE 2
#define RESP_ECHO 3
#define RESP_SHELL 4
#define RESP_CD_FAIL -1
#define RESP_CD_SUCCESS 6

// Sub statuses that are generally nice to have
#define CD_NOP 0x1

void echo(const char*);
void remove_newline(char*);
void exit_branch(const char*);
int  builtin_response(char*);
int cd_handler(char**, const int);

int main(int argc, char** argv) {
	FILE* file = NULL;
	if(argc == 2) {
		file = fopen(argv[1], "r");
		if(!file) { return 1; }
	}
	char buffer[MAX_BUF];
	while(1) {
		// determine if we're reading from stdin or a stream of some sort
		if(file == NULL && isatty(STDIN_FILENO)) {
			printf("%s", PROMPT);
			fgets(buffer, MAX_BUF, stdin);
		}
		else {
			fgets(buffer, MAX_BUF, file);
			printf("buffer: %s\n", buffer);
		}

		// Deal with EOF input
		if(!strlen(buffer)) {
			exit(0);
		}
		exit_branch(buffer);

		remove_newline(buffer);
		int status = builtin_response(buffer);
		// the switch in case we need to add more response flags later
		switch(status) {
			case RESP_ECHO: 
				echo(buffer);
			case RESP_SHELL: // shell command handler was used
				continue;
			case RESP_CD_FAIL:
				printf("msh: cd: No such file or directory\n");
		}
		memset(buffer, 0x00, MAX_BUF); // reset buffer after each usage
	}
	return 0;
}

void echo(const char* buf) {
	printf("%s\n", buf);
}


void remove_newline(char* buf) {
	char* c = buf;
	while(*c != '\n') { c++; }
	*c='\0';
}

void exit_branch(const char* buf) {
	if(!strcmp(buf, EXIT_CMD)) {
		exit(0);
	}
}

int builtin_response(char* buffer) {
#define STRING_DELIMITER " "
#define TIME_FMT "%D"
	exit_branch(buffer);	// exit is builtin so here we are
	if(!strcmp(buffer, "help")) {
		echo("enter Linux commands, or ‘exit’ to exit");
		return RESP_HELP;
	}

	// Printout the date today
	if(!strcmp(buffer, "date")) {
		static char date[64];
		time_t now = time(0);
		strftime(date, sizeof(date), TIME_FMT, localtime(&now));
		echo(date);
		return RESP_DATE;
	}



	// Populate tokens
	char *tokens[64];
	int idx = 0;
	for(char* cur = strtok(buffer, STRING_DELIMITER); cur != NULL; cur=strtok(NULL, STRING_DELIMITER)) { 
#ifdef DBG_LINE
		printf("%s ", cur);
#endif
		tokens[idx] = cur;
		idx++;
	}

	// Handling director changes
	int cd_result = cd_handler(tokens, idx);
	if(cd_result != CD_NOP) {
		return cd_result;
	}

	// Execute child process
	pid_t child = fork();
	if(child != 0) {
		int status_child = wait(NULL);
		if(status_child == 127) {
			printf("msh: %s: %d", tokens[0], status_child);
		}
	}
	else {
		execvp(tokens[0], tokens);
	}
	// Cleanup pointers
	for(int i = 0; i< 64; i++) {
		tokens[i] = NULL;
	}

}

int cd_handler(char** tokens, const int t_count) {
	if(!strcmp(tokens[0], "cd")) {
		if(t_count < 2) {
			int ret = chdir(getenv("HOME"));
			return ret;
		}
		return chdir(tokens[1]);
	}
	return CD_NOP;
}