package ltx
import "core:fmt"
import "core:os"
import "core:path/filepath"
import "core:strings"
import "core:unicode"
// TODO(Paul): change the key-value format to allow for true arbitrary string values with the use of quotes (maybe?) and make the rules clean and easy to remember.

main :: proc() {
	if len(os.args) < 2 {
		fmt.eprintf("A naive implementation of TeX-based arbitrary markup. Prints syntax tree and space-preserving XML substitution\nUsage:\n\t%s <filepath>\n", os.args[0])
		return
	}
	ltx: Ltx
	
	parse_err := ltx_parse_file(&ltx, os.args[1])
	if parse_err != .None {
		fmt.eprintln(ltx_get_error(&ltx, parse_err))
		return
	}
	for node in ltx.nodes {
		print_node(node)
	}

	sb := strings.builder_make()
	defer strings.builder_destroy(&sb)
	strip_ltx(&sb, ltx.nodes)
	strings.builder_reset(&sb)
	ltx_to_xml(&sb, ltx.nodes)
	fmt.println(strings.to_string(sb))
}

Tokens :: enum {
	Backslash,
	LeftBrace,
	RightBrace,
	LeftBracket,
	RightBracket,
	Assign,
	Quote,
}

TokenArray := [Tokens]rune {
	.Assign       = '=',
	.Backslash    = '\\',
	.LeftBrace    = '{',
	.RightBrace   = '}',
	.LeftBracket  = '[',
	.RightBracket = ']',
	.Quote        = '"',
}

Node_Kind :: enum {
	Text,
	Tag,
}

Attr_Type :: enum {
	Flag,
	Attribute,
}

Field :: struct {
	value: string,
	type:  Attr_Type,
}

Node :: struct {
	name:       string,
	kind:       Node_Kind,
	text:       string,
	attributes: map[string]Field,
	children:   [dynamic]Node,
}

Ltx_Error :: enum u32 {
	None = 0,
	EOF,
	KeyExpected,
	ClosingBracketExpected,
	ClosingBraceExpected,
	UnexpectedRightBrace,
	ValueExpected,
	KeyAlreadyExists,
	InvalidKey,
	CannotReadFile,
	// InvalidKeyStart,
}

ltx_seek :: proc(ltx: ^Ltx) -> (rune, Ltx_Error) {
	next_idx := ltx.idx + 1
	if next_idx >= len(ltx.source) do return 0, .EOF
	if ltx_current_char(ltx) == '\n' {
		ltx.pos = {
			col  = 0,
			line = ltx.pos.line + 1,
		}
	} else {
		ltx.pos.col += 1
	}
	ltx.idx = next_idx
	c := ltx_current_char(ltx)
	return c, .None
}

ltx_has_next :: proc(ltx: ^Ltx) -> b32 {
	return len(ltx.source) > ltx.idx + 1
}

ltx_peek :: proc(ltx: ^Ltx) -> (rune, Ltx_Error) {
	if !ltx_has_next(ltx) do return 0, .EOF
	return rune(ltx.source[ltx.idx + 1]), .None
}

ltx_current_char :: proc(ltx: ^Ltx) -> rune {
	assert(ltx.idx < len(ltx.source), "index cannot be greater than string length")
	return rune(ltx.source[ltx.idx])
}

ltx_consume_whitespace :: proc(ltx: ^Ltx) -> Ltx_Error {
	for unicode.is_white_space(ltx_current_char(ltx)) do ltx_seek(ltx) or_return // TODO: do prop error handling
	return .None
}

is_numeric :: proc(c: rune) -> b32 {
	return c >= '0' && c <= '9'
}

is_alpha :: proc(c: rune) -> b32 {
	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
}

validate_key :: proc(key: string) -> Ltx_Error {
	assert(len(key) > 0, "expected non-empty key")
	if !is_alpha(rune(key[0])) do return .InvalidKey
	for c in key {
		if !is_alpha(c) && !is_numeric(c) && c != '_' do return .InvalidKey
	}
	return .None
}

Ltx :: struct {
	source:      string,
	source_path: string,
	nodes:       [dynamic]Node,
	idx:         int,
	pos:         struct {
		line: u32,
		col:  u32,
	},
}

ltx_parse :: proc(ltx: ^Ltx) -> (err: Ltx_Error) {
	ltx.idx = 0
	stack := make([dynamic]Node)
	defer delete(stack)

	text_node_start_idx := 0
	for ltx_has_next(ltx) {
		if ltx_current_char(ltx) == TokenArray[.Backslash] {
			// TODO: cehck if  the char after slash is a token
			if text_node_start_idx < ltx.idx {
				node := Node {
					kind = .Text,
					text = ltx.source[text_node_start_idx:ltx.idx],
				}
				if len(stack) == 0 do append(&ltx.nodes, node)
				else do append(&stack[len(stack) - 1].children, node)
			}
			ltx_seek(ltx) or_return // skip \

			tag_start_idx := ltx.idx
			for unicode.is_letter(ltx_current_char(ltx)) do ltx_seek(ltx) or_return
			assert(tag_start_idx < ltx.idx)
			tag_name := ltx.source[tag_start_idx:ltx.idx]
			node := Node {
				kind = .Tag,
				name = tag_name,
			}
			end_pos: struct {
				tag_name: int,
				fields:   int,
				content:  int,
			} = {
				tag_name = ltx.idx,
				fields   = 0,
				content  = 0,
			}

			ltx_consume_whitespace(ltx) or_return
			for ltx_current_char(ltx) == TokenArray[.LeftBracket] {
				c := ltx_seek(ltx) or_return
				field_start := ltx.idx
				key: string
				for ltx_has_next(ltx) {
					if c == TokenArray[.Assign] {
						if field_start >= ltx.idx do return .KeyExpected
						key = strings.trim(ltx.source[field_start:ltx.idx], " \t")
						if len(key) <= 0 do return .KeyExpected
						validate_key(key) or_return
						ltx_seek(ltx) or_return
						field_start = ltx.idx
					} else if c == TokenArray[.RightBracket] {
						if field_start >= ltx.idx do return .ValueExpected
						raw_value := strings.trim(ltx.source[field_start:ltx.idx], " \t")
						if len(raw_value) <= 0 do return .ValueExpected
						value := Field{}
						if key != "" {
							value.type = .Attribute
							value.value = raw_value
						} else {
							key = raw_value
							value.type = .Flag
						}
						_, _, found := map_upsert(&node.attributes, key, value)
						if found do return .KeyAlreadyExists
						ltx_seek(ltx) or_return
						end_pos.fields = ltx.idx
						break
					}
					c = ltx_seek(ltx) or_return
				}
				ltx_consume_whitespace(ltx) or_return
			}
			ltx_consume_whitespace(ltx) or_return
			if ltx_current_char(ltx) == TokenArray[.LeftBrace] {
				ltx_seek(ltx) or_return // consume {
				append(&stack, node)
				end_pos.content = ltx.idx
			} else {
				append(&ltx.nodes, node)
			}
			if end_pos.content != 0 do text_node_start_idx = end_pos.content
			else if end_pos.fields != 0 do text_node_start_idx = end_pos.fields
			else do text_node_start_idx = end_pos.tag_name
		} else if ltx_current_char(ltx) == TokenArray[.RightBrace] {
			if len(stack) <= 0 do return .UnexpectedRightBrace
			node := pop(&stack)
			if text_node_start_idx < ltx.idx {
				text_node := Node {
					kind = .Text,
					text = ltx.source[text_node_start_idx:ltx.idx],
				}
				append(&node.children, text_node)
			}
			if len(stack) > 0 {
				append(&stack[len(stack) - 1].children, node)
			} else {
				append(&ltx.nodes, node)
			}
			ltx_seek(ltx) or_return // consume }
			text_node_start_idx = ltx.idx
		} else {
			ltx_seek(ltx) or_return
		}
	}
	if text_node_start_idx < ltx.idx {
		append(&ltx.nodes, Node{kind = .Text, text = ltx.source[text_node_start_idx:ltx.idx]})
	}
	if len(stack) > 0 do return .ClosingBraceExpected
	return .None
}

ltx_parse_file :: proc(ltx: ^Ltx, file_path: string) -> Ltx_Error {
	source, ok := os.read_entire_file(file_path)
	if !ok do return .CannotReadFile
	abs_path, abs_ok := filepath.abs(file_path)
	if !abs_ok do return .CannotReadFile
	ltx.source_path = abs_path
	ltx.source = string(source)
	return ltx_parse(ltx)
}

print_indent :: proc(level: int) {
	for i in 0 ..< level {
		fmt.print("  ")
	}
}
print_node :: proc(node: Node, indent_level := 0) {
	print_indent(indent_level)
	switch node.kind {
	case .Text:
		fmt.printf("TEXT: \"%s\"\n", escape_white_space(node.text))
	case .Tag:
		fmt.print("TAG:", node.name)
		if len(node.attributes) > 0 {
			for k, v in node.attributes {
				if v.type == .Flag do fmt.printf(" (%s)", k)
				else do fmt.printf(" {{%s: %s}}", k, v.value)
			}
		}
		fmt.println()
		if len(node.children) > 0 {
			for child in node.children {
				print_node(child, indent_level + 1)
			}
		}
	}
}

strip_ltx :: proc(sb: ^strings.Builder, nodes: [dynamic]Node) -> b32 {
	for node in nodes {
		switch node.kind {
		case .Text:
			fmt.sbprint(sb, (node.text))
		case .Tag:
			strip_ltx(sb, node.children)
		}
	}
	return true
}

ltx_to_xml :: proc(sb: ^strings.Builder, nodes: [dynamic]Node, depth := 0) {
	if len(nodes) <= 0 do return
	if depth == 0 do fmt.sbprintln(sb, "<ltx>")
	for node in nodes {
		switch node.kind {
		case .Text:
			fmt.sbprint(sb, node.text)
		case .Tag:
			fmt.sbprintf(sb, "<%s", node.name)
			for k, v in node.attributes do fmt.sbprintf(sb, " %s=\"%s\"", k, v.value)
			if len(node.children) > 0 {
				fmt.sbprint(sb, ">")
				ltx_to_xml(sb, node.children, depth + 1)
				fmt.sbprintf(sb, "</%s>", node.name)
			} else {
				fmt.sbprint(sb, " />")
			}
		}
	}
	if depth == 0 do fmt.sbprintln(sb, "</ltx>")
}

ltx_error_to_string :: proc(error: Ltx_Error) -> string {
	switch error {
	case .None:
		return ""
	case .EOF:
		return "unexpected end of file"
	case .KeyExpected:
		return "key expected before '='"
	case .ClosingBraceExpected:
		return "closing brace expected"
	case .ClosingBracketExpected:
		return "closing bracket expected"
	case .UnexpectedRightBrace:
		return "unexpected '}'"
	case .ValueExpected:
		return "value expected after '='"
	case .KeyAlreadyExists:
		return "attribute key/flag already exists in attribute"
	case .InvalidKey:
		return "invalid key"
	case .CannotReadFile:
		return "cannot read file"
	}
	return "unknown error"
}

ltx_get_error :: proc(ltx: ^Ltx, error: Ltx_Error) -> string {
	if error == .None do return ""
	file_path := len(ltx.source_path) > 0 ? ltx.source_path : "[source]"
	line := ltx.pos.line + 1
	col := ltx.pos.col + 1
	error_msg := ltx_error_to_string(error)
	return fmt.tprintf("%s(%d,%d): error: %s", file_path, line, col, error_msg)
}

escape_white_space :: proc(s: string) -> string {
	sb: strings.Builder = strings.builder_make()
	// defer strings.builder_destroy(&sb)
	for c in s {
		switch c {
		case '\t':
			fmt.sbprint(&sb, "\\t")
		case '\n':
			fmt.sbprint(&sb, "\\n")
		case:
			fmt.sbprint(&sb, c)
		}
	}
	return strings.to_string(sb)
}

process_white_space :: proc(s: string) -> string {
	sb: strings.Builder = strings.builder_make()
	defer strings.builder_destroy(&sb)
	lines := strings.split(s, "\n")
	for _line in lines {
		line := strings.trim_right(_line, "\t ")
		if len(line) <= 0 do continue
		last_idx := 0
		last_char: u8 = 0
		for i := 0; i < len(line); i += 1 {
			if line[i] == '\r' do continue
			if unicode.is_space(rune(line[i])) {
				if last_char == line[i] {
					last_idx = i
				} else {
					fmt.sbprint(&sb, line[last_idx:i])
					last_idx = i
				}
			}
			last_char = line[i]
		}
		fmt.sbprintln(&sb, line[last_idx:len(line)])
	}
	// return ""
	return strings.to_string(sb)
}