#include "AudioFile.h"

#include <iostream>
#include <iomanip>
#include <sstream>
#include <algorithm>

#include <cstdio>
#include <cstring>
#include <cerrno>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sendfile.h>

#include <unistd.h>
#include <fcntl.h>
#include <dirent.h>

#include <unicode/translit.h>
#include <unicode/unistr.h>

using namespace std;
using namespace icu;

/* TODO: we could benefit from having these dynamic, and making them
 * no-ops when the output isn't an xterm. */
#define RED     "\x1b[31m"
#define GREEN   "\x1b[32m"
#define YELLOW  "\x1b[33m"
#define BLUE    "\x1b[34m"
#define MAGENTA "\x1b[35m"
#define CYAN    "\x1b[36m"
#define RESET   "\x1b[0m"

static string base_destination;
static Transliterator *transliterator;


/* Recursive triangle. */
void process_file(const char *filename, ino_t inode);
void process_directory(const char *directory);
void process_path(const char *path);

/* Filesystem actions. */
void rename_path(const string &source, const string &stem, ino_t inode);
void make_parents(const string &filepath);

/* String generators. */
string generate_path(const AudioFile &audio);
string truncated(const string &str, const string &ext);
string transliterated(const string &str);
string strip_slash(const string &name);
void disc_track(unsigned int disc, unsigned int track, ostringstream &path);


/* Converts forward slashes to hyphens. */
string strip_slash(const string &name)
{
	string ret(name);
	replace(ret.begin(), ret.end(), '/', '-');
	return ret;
}

/* {disc}-{0-padded track}{space} with reasonable fallbacks. */
void disc_track(unsigned int disc, unsigned int discTotal, unsigned int track, ostringstream &path)
{
	if (discTotal != 1 && disc > 0) {
		path << disc;
		if (track > 0)
			path << '-';
		else
			path << ' ';
	}
	if (track > 0)
		path << setw(2) << setfill('0') << track << setw(0) << ' ';
}

/* For compilations:
 *     Various Artists/{Album Name}/{Disc/Track} {Artist} - {Title}
 * Otherwise:
 *     {Artist}/{Album}/{Disc/Track} {Title}
 * With reasonable fallbacks in case the data is partially. */
string generate_path(const AudioFile &audio)
{
	ostringstream path;
	if (audio.compilation()) {
		path << "Various Artists/";
		if (audio.album().length() == 0)
			path << "Unknown Album/";
		else
			path << strip_slash(audio.album()) << '/';
		disc_track(audio.disc(), audio.discTotal(), audio.track(), path);
		if (audio.artist().length() > 0)
			path << strip_slash(audio.artist()) << " - ";
		path << strip_slash(audio.title());
	} else {
		if (audio.artist().length() == 0)
			path << "Unknown Artist/";
		else
			path << strip_slash(audio.artist()) << '/';
		if (audio.album().length() > 0)
			path << strip_slash(audio.album()) << '/';
		disc_track(audio.disc(), audio.discTotal(), audio.track(), path);
		path << strip_slash(audio.title());
	}
	return transliterated(path.str());
}

/* Ensures that no component of the path name is bigger than 255 characters.
 * This truncates any components larger than the maximum, taking into account
 * the file extension. */
string truncated(const string &str, const string &ext)
{
	stringstream stream;
	size_t current, next = -1;
	for (;;) {
		current = next + 1;
		next = str.find_first_of('/', current);
		if (current)
			stream << '/';
		if (next == string::npos) {
			stream << str.substr(current, static_cast<size_t>(255 - ext.length())) << ext;
			break;
		}
		stream << str.substr(current, min(static_cast<size_t>(255), next - current));
	}
	return stream.str();
}

/* Uses the libicu transliterator to remove dangerous characters. Unfortuantely,
 * this requires some somewhat ugly string copying because libicu uses its own
 * type of string container. */
string transliterated(const string &str)
{
	UnicodeString in(str.c_str(), "UTF-8");
	transliterator->transliterate(in);
	char out[in.length() + 1];
	in.extract(0, in.length(), out, in.length() + 1, "ASCII");
	return out;
}

/* Replaces the base destination path with a musical note for pretty display. */
string prettify_destination(const string &str)
{
	if (str.find(base_destination) == string::npos)
		return str;
	return "\xe2\x99\xab/" + str.substr(base_destination.length());
}

/* 1. Determine the extension of the source file and convert it to lower case.
 * 2. Form destination file name from base destination, generated stem, and extension.
 * 3. If the destination file does not exist, great. Otherwise, see if it exists.
 * 4. If it exists, and the source file has the same inode as the destination, we're done.
 *    Otherwise, tag on a counter number and see if that file exists, etc.
 * 5. If we exhaust all possible counters and wrap around to 0, give up.
 * 6. After establishing a non-existing file name destination, make parent directories,
 *    then attempt to rename the source to the destination.
 * 7. If we're crossing file system barriers, copy and delete using sendfile. */
void rename_path(const string &source, const string &stem, ino_t inode)
{
	size_t pos = source.find_last_of('.');
	string ext;
	if (pos != string::npos) {
		ext = source.substr(pos);
		transform(ext.begin(), ext.end(), ext.begin(), ::tolower);
	}
	string destination = truncated(base_destination + stem, ext);
	unsigned long counter = 0;
	for (;;) {
		struct stat sbuf;
		if (stat(destination.c_str(), &sbuf)) {
			if (errno == ENOENT)
				break;
		}
		if (sbuf.st_ino == inode)
			return;
		
		ostringstream stream;
		stream << base_destination << stem << ' ' << ++counter;
		destination = truncated(stream.str(), ext);

		if (counter == 0)
			return;
	}

	make_parents(destination);
	if (!rename(source.c_str(), destination.c_str()))
		cout << CYAN << "move" << RESET << ": " << YELLOW << prettify_destination(source) << RESET << " \xe2\x86\x92 " << GREEN << prettify_destination(destination) << RESET << endl;
	else if (errno == EXDEV) {
		int source_fd = open(source.c_str(), O_RDONLY, 0);
		int destination_fd = open(destination.c_str(), O_WRONLY | O_CREAT, 0644);
		struct stat source_stat;
		if (fstat(source_fd, &source_stat))
			goto error;
		if (sendfile(destination_fd, source_fd, 0, source_stat.st_size) < 0)
			goto error;
		close(source_fd);
		close(destination_fd);
		if (unlink(source.c_str()))
			goto error;
		cout << CYAN << "copy & delete" << RESET << ": " << YELLOW << prettify_destination(source) << RESET << " \xe2\x86\x92 " << GREEN << prettify_destination(destination) << RESET << endl;
	} else
		goto error;
	return;

error:
	cerr << RED;
	perror(prettify_destination(destination).c_str());
	cerr << RESET;
}

/* Break a file path down into components and try to mkdir for each component,
 * except for the last one, ensuring that filepath's enclosing directories exist. */
void make_parents(const string &filepath)
{
	string path;
	size_t current, next = -1;
	for (;;) {
		current = next + 1;
		if ((next = filepath.find_first_of('/', current)) == string::npos)
			return;

		path.append(filepath.substr(current, next - current));
		path.append("/");

		if (!mkdir(path.c_str(), 0755))
			cout << MAGENTA << "mkdir" << RESET << ": " << prettify_destination(path) << endl;
	}
}

/* Read tags using AudioFile, and then rename the file to a generated path. */
void process_file(const char *filename, ino_t inode)
{
	AudioFile audio(filename);
	if (!audio.isValid()) {
		cerr << RED << prettify_destination(filename) << ": not a valid audio file" << RESET << endl;
		return;
	}
	rename_path(filename, generate_path(audio), inode);
}

/* Iterate through all items in given directory, skipping . and .., and process
 * each path. After, try to remove directory if it's empty. */
void process_directory(const char *directory)
{
	DIR *dir = opendir(directory);
	if (!dir)
		return;
	while (struct dirent *entry = readdir(dir)) {
		if (entry->d_name[0] == '.' && (entry->d_name[1] == '\0' ||
			(entry->d_name[1] == '.' && strlen(entry->d_name) == 2)))
			continue;

		char joined[strlen(directory) + strlen(entry->d_name) + 2];
		sprintf(joined, "%s/%s", directory, entry->d_name);
		process_path(joined);
	}
	closedir(dir);
	if (!rmdir(directory))
		cout << BLUE << "rmdir" << RESET << ": " << prettify_destination(directory) << endl;
}

/* Process files as files, directories as directories, and skip everything else. */
void process_path(const char *path)
{
	struct stat sbuf;
	if (stat(path, &sbuf)) {
		cerr << RED;
		perror(prettify_destination(path).c_str());
		cerr << RESET;
		return;
	}
	if (S_ISREG(sbuf.st_mode))
		process_file(path, sbuf.st_ino);
	else if (S_ISDIR(sbuf.st_mode))
		process_directory(path);
	else
		cerr << RED << prettify_destination(path) << ": not a file nor a directory" << RESET << endl;
}

int main(int argc, char *argv[])
{
	size_t len;
	UErrorCode status = U_ZERO_ERROR;
	/* This libicu transliterator does the following:
	 * 1. Switches to Latin.
	 * 2. Decomposes unicode.
	 * 3. Removes any special marks that aren't spaces.
	 * 4. Recomposes unicode.
	 * 5. Removes any non-ASCII chars.
	 * 6. Removes dangerous file name characters: :;*?"<>|\ */
	transliterator = Transliterator::createInstance("Latin; NFD; [:Nonspacing Mark:] Remove; NFC; [:^ASCII:] Remove; [\\:;*?\"<>|\\\\] Remove", UTRANS_FORWARD, status);
	if (!transliterator || status != U_ZERO_ERROR) {
		cerr << RED << "Fatal: Could not initialize transliterator." << RESET << endl;
		return EXIT_FAILURE;
	}

	/* We prefer MUSICDIR, but if it isn't set, we fallback to $HOME/Music/.
	 * We also take care that it ends in a / and doesn't have repeated / chars. */
	if (char *base = getenv("MUSICDIR")) {
		base_destination = base;
		if (base_destination[base_destination.length() - 1] != '/')
			base_destination.append("/");
	} else if (char *home = getenv("HOME")) {
		len = strlen(home);
		while (home[len - 1] == '/')
			home[--len] = '\0';
		base_destination = string(home) + "/Music/";
	} else {
		cerr << RED << "Fatal: Could not determine the music directory. Try setting the MUSICDIR or HOME environment variable." << RESET << endl;
		return EXIT_FAILURE;
	}
	cout << GREEN << "\xe2\x99\xab" << RESET << ": " << base_destination << endl;

	/* Process all arguments to program as input paths. */
	for (int i = 1; i < argc; ++i) {
		len = strlen(argv[i]);
		while (argv[i][len - 1] == '/')
			argv[i][--len] = '\0';
		process_path(argv[i]);
	}

	delete transliterator;
	
	return 0;
}