package os

import "base:runtime"
import "core:strconv"
import "core:unicode/utf8"

/*
	`write_string` writes a string `s` to file `f`.
	Returns the number of bytes written and an error, if any is encountered.
*/
write_string :: proc(f: ^File, s: string) -> (n: int, err: Error) {
	return write(f, transmute([]byte)s)
}

/*
	`write_strings` writes a variadic list of strings `strings` to file `f`.
	Returns the number of bytes written and an error, if any is encountered.
*/
write_strings :: proc(f: ^File, strings: ..string) -> (n: int, err: Error) {
	for s in strings {
		m: int
		m, err = write_string(f, s)
		n += m
		if err != nil {
			return
		}
	}
	return
}
/*
	`write_byte` writes a byte `b` to file `f`.
	Returns the number of bytes written and an error, if any is encountered.
*/
write_byte :: proc(f: ^File, b: byte) -> (n: int, err: Error) {
	return write(f, []byte{b})
}

/*
	`write_rune` writes a rune `r` as an UTF-8 encoded string to file `f`.
	Returns the number of bytes written and an error, if any is encountered.
*/
write_rune :: proc(f: ^File, r: rune) -> (n: int, err: Error) {
	if r < utf8.RUNE_SELF {
		return write_byte(f, byte(r))
	}

	b: [4]byte
	b, n = utf8.encode_rune(r)
	return write(f, b[:n])
}

/*
	`write_encoded_rune` writes a rune `r` as an UTF-8 encoded string which with escaped control codes to file `f`.
	Returns the number of bytes written and an error, if any is encountered.
*/
write_encoded_rune :: proc(f: ^File, r: rune) -> (n: int, err: Error) {
	wrap :: proc(m: int, merr: Error, n: ^int, err: ^Error) -> bool {
		n^ += m
		if merr != nil {
			err^ = merr
			return true
		}
		return false
	}

	if wrap(write_byte(f, '\''), &n, &err) { return }

	switch r {
	case '\a': if wrap(write_string(f, "\\a"), &n, &err) { return }
	case '\b': if wrap(write_string(f, "\\b"), &n, &err) { return }
	case '\e': if wrap(write_string(f, "\\e"), &n, &err) { return }
	case '\f': if wrap(write_string(f, "\\f"), &n, &err) { return }
	case '\n': if wrap(write_string(f, "\\n"), &n, &err) { return }
	case '\r': if wrap(write_string(f, "\\r"), &n, &err) { return }
	case '\t': if wrap(write_string(f, "\\t"), &n, &err) { return }
	case '\v': if wrap(write_string(f, "\\v"), &n, &err) { return }
	case:
		if r < 32 {
			if wrap(write_string(f, "\\x"), &n, &err) { return }
			b: [2]byte
			s := strconv.write_bits(b[:], u64(r), 16, true, 64, strconv.digits, nil)
			switch len(s) {
			case 0: if wrap(write_string(f, "00"), &n, &err) { return }
			case 1: if wrap(write_rune(f, '0'), &n, &err)    { return }
			case 2: if wrap(write_string(f, s), &n, &err)    { return }
			}
		} else {
			if wrap(write_rune(f, r), &n, &err) { return }
		}
	}
	_ = wrap(write_byte(f, '\''), &n, &err)
	return
}

/*
	`write_ptr` is a utility procedure that writes the bytes points at `data` with length `len`.

	It is equivalent to: `write(f, ([^]byte)(data)[:len])`
*/
write_ptr :: proc(f: ^File, data: rawptr, len: int) -> (n: int, err: Error) {
	return write(f, ([^]byte)(data)[:len])
}

/*
	`read_ptr` is a utility procedure that reads the bytes points at `data` with length `len`.

	It is equivalent to: `read(f, ([^]byte)(data)[:len])`
*/
read_ptr :: proc(f: ^File, data: rawptr, len: int) -> (n: int, err: Error) {
	return read(f, ([^]byte)(data)[:len])
}



/*
	`read_at_least` reads from `f` into `buf` until it has read at least `min` bytes.
	It returns the number of bytes copied and an error if fewer bytes were read.
	The error is only an `io.EOF` if no bytes were read.
*/
read_at_least :: proc(f: ^File, buf: []byte, min: int) -> (n: int, err: Error) {
	if len(buf) < min {
		return 0, .Short_Buffer
	}
	nn := max(int)
	for nn > 0 && n < min && err == nil {
		nn, err = read(f, buf[n:])
		n += nn
	}
	if n >= min {
		err = nil
	}
	return
}

/*
	`read_full` reads exactly `len(buf)` bytes from `f` into `buf`.
	It returns the number of bytes copied and an error if fewer bytes were read.
	The error is only an `io.EOF` if no bytes were read.

	It is equivalent to `read_at_least(f, buf, len(buf))`.
*/
read_full :: proc(f: ^File, buf: []byte) -> (n: int, err: Error) {
	return read_at_least(f, buf, len(buf))
}



read_entire_file :: proc{
	read_entire_file_from_path,
	read_entire_file_from_file,
}

/*
	`read_entire_file_from_path` reads the entire named file `name` into memory allocated with `allocator`.
	A slice of bytes and an error is returned, if any error is encountered.
*/
@(require_results)
read_entire_file_from_path :: proc(name: string, allocator: runtime.Allocator, loc := #caller_location) -> (data: []byte, err: Error) {
	f, ferr := open(name)
	if ferr != nil {
		return nil, ferr
	}
	defer close(f)
	return read_entire_file_from_file(f=f, allocator=allocator, loc=loc)
}

/*
	`read_entire_file_from_file` reads the entire file `f` into memory allocated with `allocator`.
	A slice of bytes and an error is returned, if any error is encountered.
*/
@(require_results)
read_entire_file_from_file :: proc(f: ^File, allocator: runtime.Allocator, loc := #caller_location) -> (data: []byte, err: Error) {
	size: int
	has_size := false
	if size64, serr := file_size(f); serr == nil {
		if i64(int(size64)) == size64 {
			has_size = true
			size = int(size64)
		}
	}

	if has_size && size > 0 {
		total: int
		data = make([]byte, size, allocator, loc) or_return
		for total < len(data) {
			n: int
			n, err = read(f, data[total:])
			total += n
			if err != nil {
				if err == .EOF {
					err = nil
				}
				data = data[:total]
				break
			}
		}
		return
	} else {
		buffer: [1024]u8
		out_buffer := make([dynamic]u8, 0, 0, allocator, loc)
		total := 0
		for {
			n: int
			n, err = read(f, buffer[:])
			total += n
			append_elems(&out_buffer, ..buffer[:n], loc=loc) or_return
			if err != nil {
				if err == .EOF || err == .Broken_Pipe {
					err = nil
				}
				data = out_buffer[:total]
				return
			}
		}
	}
}

/*
	`write_entire_file` writes the contents of `data` into named file `name`.
	It defaults with the permssions `perm := Permissions_Read_All + {.Write_User}`, and `truncate`s by default.
	An error is returned if any is encountered.
*/
write_entire_file :: proc{
	write_entire_file_from_bytes,
	write_entire_file_from_string,
}

/*
	`write_entire_file_from_bytes` writes the contents of `data` into named file `name`.
	It defaults with the permssions `perm := Permissions_Read_All + {.Write_User}`, and `truncate`s by default.
	An error is returned if any is encountered.
*/
@(require_results)
write_entire_file_from_bytes :: proc(name: string, data: []byte, perm := Permissions_Read_All + {.Write_User}, truncate := true) -> Error {
	flags := O_WRONLY|O_CREATE
	if truncate {
		flags |= O_TRUNC
	}
	f := open(name, flags, perm) or_return
	_, err := write(f, data)
	if cerr := close(f); cerr != nil && err == nil {
		err = cerr
	}
	return err
}



/*
	`write_entire_file_from_string` writes the contents of `data` into named file `name`.
	It defaults with the permssions `perm := Permissions_Read_All + {.Write_User}`, and `truncate`s by default.
	An error is returned if any is encountered.
*/
@(require_results)
write_entire_file_from_string :: proc(name: string, data: string, perm := Permissions_Read_All + {.Write_User}, truncate := true) -> Error {
	return write_entire_file(name, transmute([]byte)data, perm, truncate)
}