#include "std/base.toc", base;
#include "std/mem.toc", mem;

str_to_cstr ::= fn(s: []char) []char {
	ret := mem.news(char, s.len+1);
	mem.mem_copy(&ret[0], &s[0], s.len);
	return ret;
}

// @TODO(eventually): enum
FileError ::= int;
FILE_ERR_OK ::= 0;
FILE_ERR_EOF ::= 1;
FILE_ERR_MISC ::= 2;
// @TODO: more of these

/*
the raw file interface:
raw_stdout - standard output
raw_stderr - standard error
raw_stdin - standard input
raw_file_read - read from a raw file - unlike raw_file_write, it's okay if the number of bytes read doesn't match the number of bytes requested, but if 0 bytes are read, it is assumed to be the end of the file
raw_file_write - write to a raw file
raw_file_open_write - open a raw file for writing
raw_file_open_read - open a raw file for reading
raw_file_close - close a raw file
*/


#if base.PLATFORM_IS_UNIX {
	// @TODO: use syscall instead (it'll allow other functions called write)
	write ::= #foreign("write", base.libc) fn(#C int, #C &"const void", #C size_t) #C long;
	read ::= #foreign("read", base.libc) fn(#C int, &void, #C size_t) #C long;
	open ::= #foreign("open", base.libc) fn (#C &"const char", #C int, #C unsigned) #C int;
	close ::= #foreign("close", base.libc) fn (#C int) #C int;

	DEFAULT_MODE ::= 0o644;

	O_RDONLY ::= 0x00;
	O_WRONLY ::= 0x01;
	O_CREAT  ::= 0x40;

	RawFile ::= int;
	raw_file_write ::= fn(file: RawFile, buf: &void, size: int) err : FileError {
		while size > 0 {
			bytes_written := write(file as #C int, buf, size as #C size_t);
			if bytes_written < 0 {
				err = FILE_ERR_MISC; // @TODO
				return;
			}
			size -= bytes_written;
			buf += bytes_written;
		}
	}
	raw_file_read ::= fn(file: RawFile, buf: &void, size: int) n: int, err : FileError {
		bytes_read := read(file as #C int, buf, size as #C size_t);
		if bytes_read < 0 {
			err = FILE_ERR_MISC;
			return;
		}
		n = bytes_read;
	}
	raw_stdout ::= fn() RawFile {
		return 1;
	}
	raw_stderr ::= fn() RawFile {
		return 2;
	}
	raw_stdin ::= fn() RawFile {
		return 0;
	}
	raw_file_open_write ::= fn(name: []char) f: RawFile, err : FileError {
		cstr := str_to_cstr(name);
		defer mem.dels(cstr);
		// @TODO: switch to bitwise or when that exists
		f = open(&cstr[0], (O_WRONLY + O_CREAT) as #C int, DEFAULT_MODE as #C unsigned) as RawFile;
		if f == -1 {
			err = FILE_ERR_MISC; // @TODO
		}
	}
	raw_file_open_read ::= fn(name: []char) f: RawFile, err : FileError {
		cstr := str_to_cstr(name);
		defer mem.dels(cstr);
		f = open(&cstr[0], O_RDONLY as #C int, 0) as RawFile;
		if f == -1 {
			err = FILE_ERR_MISC; // @TODO
		}
	}
	raw_file_close ::= fn(f: RawFile) err : FileError {
		if close(f as #C int) == -1 {
			err = FILE_ERR_MISC; // @TODO
		}
	}
} else {
	// @TODO: test this interface
	// @TODO: on windows, use WriteFile
	fwrite ::= #foreign("fwrite", base.libc) fn(#C &"const void", #C size_t, #C size_t, &void) #C size_t;
	fread ::= #foreign("fread", base.libc) fn(&void, #C size_t, #C size_t, &void) #C size_t;
	RawFile ::= &void;
	// @TODO: Use FileErrors
	raw_file_write ::= fn(file: RawFile, buf: &void, size: int) bool {
		bytes_written := fwrite(buf, 1, size, file) as int;
		return bytes_written == size;
	}
	raw_file_read ::= fn(file: RawFile, buf: &void, size: int) bool {
		bytes_read := fread(buf, 1, size, file) as int;
		return bytes_read == size;

	}
	raw_stdout ::= fn() RawFile {
		return #builtin("stdout");
	}
	raw_stderr ::= fn() RawFile {
		return #builtin("stderr");
	}
	raw_stdin ::= fn() RawFile {
		return #builtin("stdin");
	}
	raw_file_open_write ::= fn(name: []char) f: RawFile, err : FileError {
		cstr := base.str_to_cstr(name);
		defer mem.dels(cstr);
		mode := "wb\0";
		f = fopen(&cstr[0], &mode[0]);
		if f == null {
			err = FILE_ERR_MISC; // @TODO
		}
	}
	raw_file_open_read ::= fn(name: []char) f: RawFile, err : FileError {
		cstr := base.str_to_cstr(name);
		defer mem.dels(cstr);
		mode := "rb\0";
		f = fopen(&cstr[0], &mode[0]);
		if f == null {
			err = FILE_ERR_MISC; // @TODO
		}
	}
	raw_file_close ::= fn(f: RawFile) err : FileError {
		if fclose(f) != 0 {
			err = FILE_ERR_MISC; // @TODO
		}
	}
}

// file modes
FileMode ::= u8;
// @TODO: enum
MODE_READ  :: FileMode = 1;
MODE_WRITE :: FileMode = 2;


IO_DEBUG ::= base.DEBUG;

// @TODO: error flag
// @TODO: locking?
File ::= struct {
	BUFSZ ::= 4096;
	raw : RawFile;
	buffer_used, buffer_len : int; // range from 0 to FILE_BUFSZ-1
	mode : FileMode;
	eof : bool;
	nobuffer : bool; // if true, flush after every write
	buffer : [BUFSZ]char;
}

raw_file_to_file ::= fn(raw : RawFile, mode : FileMode, f: &File) {
	f.raw = raw;
	f.mode = mode;
}

std_in, std_out, std_err : File;

fopen_write ::= fn(name: []char) f: &File, error: FileError {
	raw : RawFile;
	raw, error = raw_file_open_write(name);
	if !error {
		f = mem.new(File);
		raw_file_to_file(raw, MODE_WRITE, f);
	}
}

fopen_read ::= fn(name: []char) f: &File, error: FileError {
	raw : RawFile;
	raw, error = raw_file_open_read(name);
	if !error {
		f = mem.new(File);
		raw_file_to_file(raw, MODE_READ, f);
	}
}

flush ::= fn(use f: &File) err: FileError {
	if mode == MODE_READ {
		// discard buffer
		buffer_used = 0;
		buffer_len = 0;
	} else {
		err = raw_file_write(raw, &buffer[0], buffer_used);
		buffer_used = 0;
	}
}

fclose ::= fn(f: &File) err: FileError {
	flush(f);
	err = raw_file_close(f.raw);
	mem.del(f);
}

can_write ::= fn(mode: FileMode) bool {
	return mode == MODE_WRITE;
}

can_read ::= fn(mode: FileMode) bool {
	return mode == MODE_READ;
}

fwrites ::= fn(use f: &File, s : []char) FileError {
	#if IO_DEBUG {
		if !can_write(mode) {
			base.error("Writing to file which wasn't opened for writing.");
		}
	}

	if f.nobuffer {
		return raw_file_write(raw, &s[0], s.len);
	}
	if buffer_used + s.len > BUFSZ {
		flush(f);
		if s.len > BUFSZ {
			return raw_file_write(raw, &s[0], s.len);
		} else {
			mem.mem_copy(&buffer[0], &s[0], s.len);
			buffer_used = s.len;
			return FILE_ERR_OK;
		}
	} else {
		mem.mem_copy(&buffer[buffer_used], &s[0], s.len);
		buffer_used += s.len;
		return FILE_ERR_OK;
	}
}

fputs ::= fn(f: &File, s: []char) err : FileError {
	err = fwrites(f, s);
	if !err {
		err = fwrites(f, "\n");
	}
}

writes ::= fn(s: []char) {
	fwrites(&std_out, s);
}

puts ::= fn(s: []char) {
	fputs(&std_out, s);
}

fwritei ::= fn(use f: &File, x: int) err : FileError {
	#if IO_DEBUG {
		if !can_write(mode) {
			base.error("Writing to file which wasn't opened for writing.");
		}
	}
	max_int_len ::= 20; // maximum length of a 64-bit integer, converted to a string
	if buffer_used > BUFSZ - max_int_len {
		err = flush(f);
		if err { return; }
	}

	out := &buffer[buffer_used];
	start := out;

	defer buffer_used = out - start;

	// flush at end if file is not buffered
	defer if nobuffer {
		err = flush(f);
	}


	x_unsigned : u64;

	if x > 0 {
		x_unsigned = x as u64;
	} elif x < 0 {
		*out = '-';
		out += 1;
		// get the absolute value of x in a u64. this complicated stuff is needed because -INT_MIN doesn't fit in a 64-bit signed integer 
		x_unsigned = (18446744073709551615 - (x as u64)) + 1;
	} else {
		*out = '0';
		out += 1;
		return;
	}	
	
	scan_digit : u64 = 1000000000000000000;
	started := false;
	while scan_digit > 0 {
		digit := (x_unsigned / scan_digit) % 10;
		if digit > 0 { started = true; }
		if started {
			*out = (('0' as u64) + digit) as char;
			out += 1;
		}
		scan_digit /= 10;
	}
}

writei ::= fn(x: int) {
	fwritei(&std_out, x);
}

puti ::= fn(x: int) {
	writei(x);
	writes("\n");
}

putb ::= fn(x: bool)  {
	if x {
		writes("true\n");
	} else {
		writes("false\n");
	}
}

// read into out, set its length appropriately
fread ::= fn(use f: &File, out: &[]char) FileError {
	#if IO_DEBUG {
		if !can_read(mode) {
			base.error("Reading from file which wasn't opened for reading.");
		}
	}
	if eof {
		out.len = 0;
		return FILE_ERR_EOF;
	}
	to_read := out.len;
	buffer_left := buffer_len - buffer_used;
	if to_read <= buffer_left {
		mem.mem_copy(&out[0], &buffer[buffer_used], to_read);
		buffer_used += to_read;
		return FILE_ERR_OK;
	} else {
		mem.mem_copy(&out[0], &buffer[buffer_used], buffer_left);
		out_idx := buffer_left;
		to_read -= buffer_left;
		if to_read > BUFSZ {
			// very big read, just do it directly
			buffer_used = 0;
			buffer_len = 0;
			n, err := raw_file_read(raw, &out[out_idx], to_read);
			if n == 0 {
				eof = true;
			}
			out.len = n + buffer_left;
			if err {
				return err;
			}
		} elif to_read > 0 {
			n, err := raw_file_read(raw, &buffer[0], BUFSZ);
			if n == 0 {
				eof = true;
			}
			buffer_len = n;
			if n < to_read {
				// we didn't read out.len bytes
				out.len = n + buffer_left;
				to_read = n;
			}
			if err {
				buffer_used = 0;
				return err;
			}
			mem.mem_copy(&out[out_idx], &buffer[0], to_read);
			buffer_used = to_read;
		}
		return FILE_ERR_OK;
	}
}


// read a line from standard input. does not include newline
gets ::= fn(out: &[]char) err : FileError {
	err = fread(&std_in, out);
	if out.len && out[out.len-1] == '\n' {
		out.len -= 1;
	}
}

// read a line of standard input, at most max_len (default: 256) characters
// a read error might happen, but this function just ignores it
read_line ::= fn(max_len := 256) []char {
	ret := mem.news(char, max_len);
	gets(&ret);
	return ret;
}

io_init ::= fn() {
	raw_file_to_file(raw_stdout(), MODE_WRITE, &std_out);
	std_out.nobuffer = true;
	raw_file_to_file(raw_stderr(), MODE_WRITE, &std_err);
	std_err.nobuffer = true;
	raw_file_to_file(raw_stdin(), MODE_READ, &std_in);
}

#init io_init();