/**
	Thread based asynchronous file I/O fallback implementation

	Copyright: © 2012 RejectedSoftware e.K.
	Authors: Sönke Ludwig
	License: Subject to the terms of the MIT license, as written in the included LICENSE.txt file.
*/
module vibe.core.drivers.threadedfile;

import vibe.core.core : yield;
import vibe.core.log;
import vibe.core.driver;
import vibe.utils.string;

import std.algorithm;
import std.conv;
import std.exception;
import std.string;
import core.stdc.errno;

version(Posix){
	import core.sys.posix.fcntl;
	import core.sys.posix.sys.stat;
	import core.sys.posix.unistd;
}
version(Windows){
	import core.sys.windows.stat;

	private {
		// TODO: use CreateFile/HANDLE instead of the Posix API on Windows

		extern(C) {
			alias off_t = sizediff_t;
			int open(in char* name, int mode, ...);
			int chmod(in char* name, int mode);
			int close(int fd);
			int read(int fd, void *buffer, uint count);
			int write(int fd, in void *buffer, uint count);
			off_t lseek(int fd, off_t offset, int whence);
		}

		enum O_RDONLY = 0;
		enum O_WRONLY = 1;
		enum O_RDWR = 2;
		enum O_APPEND = 8;
		enum O_CREAT = 0x0100;
		enum O_TRUNC = 0x0200;
		enum O_BINARY = 0x8000;

		enum _S_IREAD = 0x0100;          /* read permission, owner */
		enum _S_IWRITE = 0x0080;          /* write permission, owner */
		alias stat_t = struct_stat;
	}
}
else
{
	enum O_BINARY = 0;
}

private {
	enum SEEK_SET = 0;
	enum SEEK_CUR = 1;
	enum SEEK_END = 2;
}

final class ThreadedFileStream : FileStream {
@safe:

	private {
		int m_fileDescriptor;
		Path m_path;
		ulong m_size;
		ulong m_ptr = 0;
		FileMode m_mode;
		bool m_ownFD = true;
	}

	this(Path path, FileMode mode)
	{
		auto pathstr = path.toNativeString();
		() @trusted {
			final switch(mode) {
				case FileMode.read:
					m_fileDescriptor = open(pathstr.toStringz(), O_RDONLY|O_BINARY);
					break;
				case FileMode.readWrite:
					m_fileDescriptor = open(pathstr.toStringz(), O_RDWR|O_BINARY);
					break;
				case FileMode.createTrunc:
					m_fileDescriptor = open(pathstr.toStringz(), O_RDWR|O_CREAT|O_TRUNC|O_BINARY, octal!644);
					break;
				case FileMode.append:
					m_fileDescriptor = open(pathstr.toStringz(), O_WRONLY|O_CREAT|O_APPEND|O_BINARY, octal!644);
					break;
			}
		} ();

		if( m_fileDescriptor < 0 )
			//throw new Exception(format("Failed to open '%s' with %s: %d", pathstr, cast(int)mode, errno));
			throw new Exception("Failed to open file '"~pathstr~"'.");

		this(m_fileDescriptor, path, mode);
	}

	this(int fd, Path path, FileMode mode)
	{
		assert(fd >= 0);
		m_fileDescriptor = fd;
		m_path = path;
		m_mode = mode;

		version(linux){
			// stat_t seems to be defined wrong on linux/64
			m_size = .lseek(m_fileDescriptor, 0, SEEK_END);
		} else {
			stat_t st;
			() @trusted { fstat(m_fileDescriptor, &st); } ();
			m_size = st.st_size;

			// (at least) on windows, the created file is write protected
			version(Windows){
				if( mode == FileMode.createTrunc )
					() @trusted { chmod(path.toNativeString().toStringz(), S_IREAD|S_IWRITE); } ();
			}
		}
		() @trusted { lseek(m_fileDescriptor, 0, SEEK_SET); } ();

		logDebug("opened file %s with %d bytes as %d", path.toNativeString(), m_size, m_fileDescriptor);
	}

	~this()
	{
		close();
	}

	@property int fd() { return m_fileDescriptor; }
	@property Path path() const { return m_path; }
	@property bool isOpen() const { return m_fileDescriptor >= 0; }
	@property ulong size() const { return m_size; }
	@property bool readable() const { return m_mode != FileMode.append; }
	@property bool writable() const { return m_mode != FileMode.read; }

	void takeOwnershipOfFD()
	{
		enforce(m_ownFD);
		m_ownFD = false;
	}

	void seek(ulong offset)
	{
		version (Win32) {
			enforce(offset <= off_t.max, "Cannot seek above 4GB on Windows x32.");
			auto pos = () @trusted { return .lseek(m_fileDescriptor, cast(off_t)offset, SEEK_SET); } ();
		} else auto pos = () @trusted { return .lseek(m_fileDescriptor, offset, SEEK_SET); } ();
		enforce(pos == offset, "Failed to seek in file.");
		m_ptr = offset;
	}

	ulong tell() { return m_ptr; }

	void close()
	{
		if( m_fileDescriptor != -1 && m_ownFD ){
			() @trusted { .close(m_fileDescriptor); } ();
			m_fileDescriptor = -1;
		}
	}

	@property bool empty() const { assert(this.readable); return m_ptr >= m_size; }
	@property ulong leastSize() const { assert(this.readable); return m_size - m_ptr; }
	@property bool dataAvailableForRead() { return true; }

	const(ubyte)[] peek()
	{
		return null;
	}

	alias read = Stream.read;
	size_t read(scope ubyte[] dst, IOMode)
	{
		assert(this.readable);
		size_t len = dst.length;
		while (dst.length > 0) {
			enforce(dst.length <= leastSize);
			auto sz = min(dst.length, 4096);
			enforce(() @trusted { return .read(m_fileDescriptor, dst.ptr, cast(int)sz); } () == sz, "Failed to read data from disk.");
			dst = dst[sz .. $];
			m_ptr += sz;
			yield();
		}
		return len;
	}

	alias write = Stream.write;
	size_t write(in ubyte[] bytes_, IOMode)
	{
		const(ubyte)[] bytes = bytes_;
		assert(this.writable);
		size_t len = bytes_.length;
		while (bytes.length > 0) {
			auto sz = min(bytes.length, 4096);
			auto ret = () @trusted { return .write(m_fileDescriptor, bytes.ptr, cast(int)sz); } ();
			enforce(ret == sz, "Failed to write data to disk."~to!string(sz)~" "~to!string(errno)~" "~to!string(ret)~" "~to!string(m_fileDescriptor));
			bytes = bytes[sz .. $];
			m_ptr += sz;
			yield();
		}
		return len;
	}

	void flush()
	{
		assert(this.writable);
	}

	void finalize()
	{
		flush();
	}
}

unittest { // issue #1189
	auto fil = new ThreadedFileStream(Path(".unittest.tmp"), FileMode.createTrunc);
	scope (exit) {
		fil.close();
		removeFile(".unittest.tmp");
	}
	immutable(ubyte)[] msg = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
	fil.write(msg);
	fil.seek(5);
	ubyte[3] buf;
	fil.read(buf);
	assert(buf == [5, 6, 7]);
}