#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdbool.h>
#include <unistd.h>
#include "util.h"
#include "io.h"

#include <limits.h>
#ifndef PATH_MAX
#ifdef __linux__
#include <linux/limits.h>
#else
#define PATH_MAX 512
#endif
#endif

char* strtail(char* str, int len, int count) {
	int index = len - count;
	if (index <= 0) return str;
	return str + (sizeof(char) * (index));
}

char* strhead(char* str, int count) {
	return str + (sizeof(char) * count);
}

char* trimstr(char* str, int len, int end) {
	int count = len - end;
	char oldchar = str[count];
	str[count] = '\0';
	char* newstr = (char*)malloc(sizeof(char) * (1 + count));
	strcpy(newstr, str);
	str[count] = oldchar;
	return newstr;
}

char* getname(char* f, int len) {
	int startind = 0;
	int endind = len - 1;
	bool readsmt = false;
 
	for(int i = endind; i >= 0; i--) {
		if(f[i] == '/') {
			if(!readsmt) {
				endind = i-1;
				f[i] = '\0';
				continue;
			}
			startind = i+1;
			break;
		}
		readsmt = true;
	}

	int sz = sizeof(char)*(endind - startind + 2);
	char* startstr = strhead(f, startind);
	char* retstr = (char*)malloc(sz);
	snprintf(retstr, sz, "%s", startstr);
	return retstr;
}

char* getfullname(char* fname, int fnamelen, char* dirname, int dirlen) {
	int sz = sizeof(char)*(fnamelen+dirlen+2);
	char* fullname = (char*)malloc(sz);
	sprintf(fullname, "%s/%s", dirname, fname);
	return fullname;
}

bool isdotjack(char* f, int len) {
	const char* ext = ".jack";
	return strcmp(strtail(f, len, strlen(ext)), ext) == 0;
}

bool isdir(char* f, int len) {
	bool readsmt = false;
	for(int i = len-1; i >= 0; i--) {
		if(f[i] == '.') {
			if(readsmt)
				return false;
			else
				continue;
		}
		if(f[i] == '/')
			return 1;
		readsmt = true;
	}
	return true;
}

char* getoutname(char* fullname, int len) {
	char* trimmed = trimstr(fullname, len, 4);
	int sz = sizeof(char) * (len-1);
	char* outname = (char*)malloc(sz);
	sprintf(outname, "%svm", trimmed);
	free(trimmed);
	return outname;
}

FILELIST* addfile(FILELIST* l, char* fullname, char* name) {
	FILELIST* new = (FILELIST*)malloc(sizeof(FILELIST));
	new->name = name;
	new->fullname = fullname;
	new->next = l;
	new->outname = getoutname(fullname, strlen(fullname));
	return new;
}

FILELIST* getfilesfromdir(char* dir) {
	FILELIST* filelist = NULL;
	DIR* d = opendir(dir);

	if(d == NULL) {
		eprintf("Error while opening directory '%s': %s\n", dir, strerror(errno));
		exit(errno);
	}

	int len = strlen(dir);
	struct dirent* thisfile;
	while(thisfile = readdir(d), thisfile != NULL) {
		int thislen = strlen(thisfile->d_name);
		if(isdotjack(thisfile->d_name, thislen)) {
			char* fullname = getfullname(thisfile->d_name, thislen, dir, len);
			char* name = ezheapstr(thisfile->d_name);
			filelist = addfile(filelist, fullname, name);
		}
	}
	
	closedir(d);

	if(filelist == NULL) {
		eprintf("Directory '%s' doesn't have any .jack file\n", dir);
		exit(1);
	}
	return filelist;
}

FILELIST* getsinglefile(char* file) {
	int len = strlen(file);
	if(isdotjack(file, len)){
		char* name = getname(file, len);
		char* fullname = heapstr(file, len);

		FILE* input = fopen(fullname, "r");
		if(input == NULL) {
			eprintf("Error while reading file '%s': %s\n", file, strerror(errno));
			exit(errno);
		}
		fclose(input);

		return addfile(NULL, fullname, name);
	}
	else {
		eprintf("Input file must be named like 'Xxx.vm'\n");
		exit(1);
	}
}

FILELIST* getfiles(char* input) {
	int inplen = strlen(input);
	bool isitdir = isdir(input, inplen);

	if(isitdir)
		return getfilesfromdir(input);
	else
		return getsinglefile(input);
}

void freefilelist(FILELIST* fs) {
	free(fs->name);
	free(fs->fullname);
	free(fs->outname);
	FILELIST* next = fs->next;
	free(fs);
	if(next != NULL)
		freefilelist(next);
}