package flags

import "core:fmt"
@require import "core:os"
@require import "core:path/filepath"
import "core:strings"

/*
Parse any arguments into an annotated struct or exit if there was an error.

*Allocates Using Provided Allocator*

This is a convenience wrapper over `parse` and `print_errors`.

Inputs:
- model: A pointer to an annotated struct.
- program_args: A slice of strings, usually `os.args`.
- style: The argument parsing style.
- allocator: (default: context.allocator)
- loc: The caller location for debugging purposes (default: #caller_location)
*/
@(optimization_mode="favor_size")
parse_or_exit :: proc(
	model: ^$T,
	program_args: []string,
	style: Parsing_Style = .Odin,
	allocator := context.allocator,
	loc := #caller_location,
) {
	assert(len(program_args) > 0, "Program arguments slice is empty.", loc)

	program := filepath.base(program_args[0])
	args: []string

	if len(program_args) > 1 {
		args = program_args[1:]
	}

	error := parse(model, args, style)
	if error != nil {
		stderr := os.stream_from_handle(os.stderr)

		if len(args) == 0 {
			// No arguments entered, and there was an error; show the usage,
			// specifically on STDERR.
			write_usage(stderr, T, program, style)
			fmt.wprintln(stderr)
		}

		print_errors(T, error, program, style)

		_, was_help_request := error.(Help_Request)
		os.exit(0 if was_help_request else 1)
	}
}
/*
Print out any errors that may have resulted from parsing.

All error messages print to STDERR, while usage goes to STDOUT, if requested.

Inputs:
- data_type: The typeid of the data structure to describe, if usage is requested.
- error: The error returned from `parse`.
- style: The argument parsing style, required to show flags in the proper style, when usage is shown.
*/
@(optimization_mode="favor_size")
print_errors :: proc(data_type: typeid, error: Error, program: string, style: Parsing_Style = .Odin) {
	stderr := os.stream_from_handle(os.stderr)
	stdout := os.stream_from_handle(os.stdout)

	switch specific_error in error {
	case Parse_Error:
		fmt.wprintfln(stderr, "[%T.%v] %s", specific_error, specific_error.reason, specific_error.message)
	case Open_File_Error:
		fmt.wprintfln(stderr, "[%T#%i] Unable to open file with perms 0o%o in mode 0x%x: %s",
			specific_error,
			specific_error.errno,
			specific_error.perms,
			specific_error.mode,
			specific_error.filename)
	case Validation_Error:
		fmt.wprintfln(stderr, "[%T] %s", specific_error, specific_error.message)
	case Help_Request:
		write_usage(stdout, data_type, program, style)
	}
}
/*
Get the value for a subtag.

This is useful if you need to parse through the `args` tag for a struct field
on a custom type setter or custom flag checker.

Example:

	import "core:flags"
	import "core:fmt"

	subtag_example :: proc() {
		args_tag := "precision=3,signed"

		precision, has_precision := flags.get_subtag(args_tag, "precision")
		signed, is_signed := flags.get_subtag(args_tag, "signed")

		fmt.printfln("precision = %q, %t", precision, has_precision)
		fmt.printfln("signed = %q, %t", signed, is_signed)
	}

Output:

	precision = "3", true
	signed = "", true

*/
get_subtag :: proc(tag, id: string) -> (value: string, ok: bool) {
	// This proc was initially private in `internal_rtti.odin`, but given how
	// useful it would be to custom type setters and flag checkers, it lives
	// here now.

	tag := tag

	for subtag in strings.split_iterator(&tag, ",") {
		if equals := strings.index_byte(subtag, '='); equals != -1 && id == subtag[:equals] {
			return subtag[1 + equals:], true
		} else if id == subtag {
			return "", true
		}
	}

	return
}