export const WORDS_DOCUMENT_VERSION = 1;

export type WordsMark = 'bold' | 'italic' | 'underline' | 'strike' | 'code';
export type WordsBlockType = 'paragraph' | 'heading' | 'quote' | 'code' | 'list' | 'table';
export type WordsListKind = 'ordered' | 'unordered' | 'check';
export type WordsHeadingLevel = 1 | 2 | 3;
export type WordsTextAlign = 'left' | 'center' | 'right' | 'justify';

// Table types live in the table extension since F2.3 (extension system
// migration). Re-exported here so existing consumers that import table
// types from `engine/document` keep compiling. New code SHOULD import
// from `extensions/table` directly.
import type {
	WordsTableCellVerticalAlign,
	WordsTableCellTone,
	WordsTableBlock,
	WordsTableRow,
	WordsTableCell,
	WordsTableOptions,
	WordsTableCellOptions
} from '../extensions/table/types';
export type {
	WordsTableCellVerticalAlign,
	WordsTableCellTone,
	WordsTableBlock,
	WordsTableRow,
	WordsTableCell,
	WordsTableOptions,
	WordsTableCellOptions
};

export interface WordsDocument {
	readonly version: typeof WORDS_DOCUMENT_VERSION;
	readonly children: readonly WordsBlock[];
}

export type WordsBlock =
	| WordsParagraphBlock
	| WordsHeadingBlock
	| WordsQuoteBlock
	| WordsCodeBlock
	| WordsListBlock
	| WordsTableBlock;

export interface WordsParagraphBlock {
	readonly type: 'paragraph';
	readonly children: readonly WordsInline[];
	readonly textAlign?: WordsTextAlign;
}

export interface WordsHeadingBlock {
	readonly type: 'heading';
	readonly level: WordsHeadingLevel;
	readonly children: readonly WordsInline[];
	readonly textAlign?: WordsTextAlign;
}

export interface WordsQuoteBlock {
	readonly type: 'quote';
	readonly children: readonly WordsInline[];
	readonly textAlign?: WordsTextAlign;
}

export interface WordsCodeBlock {
	readonly type: 'code';
	readonly children: readonly WordsInline[];
	readonly language?: string;
}

export interface WordsListBlock {
	readonly type: 'list';
	readonly kind: WordsListKind;
	readonly children: readonly WordsListItem[];
}

export interface WordsListItem {
	readonly type: 'list-item';
	readonly checked?: boolean;
	readonly indent?: number;
	readonly children: readonly WordsInline[];
}

// Table interface declarations live in `extensions/table/types.ts` since
// F2.3. The interfaces (WordsTableBlock, WordsTableRow, WordsTableCell,
// WordsTableOptions, WordsTableCellOptions) are re-exported from this
// module via the `export type { ... } from '../extensions/table/types'`
// statement near the top of the file.

export type WordsInline = WordsText | WordsLink;

export interface WordsText {
	readonly type: 'text';
	readonly text: string;
	readonly marks?: readonly WordsMark[];
}

export interface WordsLink {
	readonly type: 'link';
	readonly href: string;
	readonly title?: string;
	readonly children: readonly WordsInline[];
}

export const WORDS_MARKS = [
	'bold',
	'italic',
	'underline',
	'strike',
	'code'
] as const satisfies readonly WordsMark[];
export const WORDS_LIST_KINDS = [
	'ordered',
	'unordered',
	'check'
] as const satisfies readonly WordsListKind[];
export const WORDS_HEADING_LEVELS = [1, 2, 3] as const satisfies readonly WordsHeadingLevel[];
export const WORDS_TEXT_ALIGNS = [
	'left',
	'center',
	'right',
	'justify'
] as const satisfies readonly WordsTextAlign[];
export const WORDS_TABLE_CELL_VERTICAL_ALIGNS = [
	'top',
	'middle',
	'bottom'
] as const satisfies readonly WordsTableCellVerticalAlign[];
export const WORDS_TABLE_CELL_TONES = [
	'default',
	'muted',
	'accent'
] as const satisfies readonly WordsTableCellTone[];

export function createEmptyWordsDocument(): WordsDocument {
	return {
		version: WORDS_DOCUMENT_VERSION,
		children: [createParagraph()]
	};
}

export function createParagraph(
	children: readonly WordsInline[] = [createText('')],
	textAlign?: WordsTextAlign
): WordsParagraphBlock {
	return { type: 'paragraph', children, ...(textAlign ? { textAlign } : {}) };
}

export function createHeading(
	level: WordsHeadingLevel,
	children: readonly WordsInline[] = [createText('')],
	textAlign?: WordsTextAlign
): WordsHeadingBlock {
	return { type: 'heading', level, children, ...(textAlign ? { textAlign } : {}) };
}

export function createQuote(
	children: readonly WordsInline[] = [createText('')],
	textAlign?: WordsTextAlign
): WordsQuoteBlock {
	return { type: 'quote', children, ...(textAlign ? { textAlign } : {}) };
}

export function createCodeBlock(
	children: readonly WordsInline[] = [createText('')],
	language?: string
): WordsCodeBlock {
	const normalizedLanguage = normalizeWordsCodeLanguage(language);
	return {
		type: 'code',
		children,
		...(normalizedLanguage ? { language: normalizedLanguage } : {})
	};
}

export function createList(
	kind: WordsListKind,
	children: readonly WordsListItem[] = [createListItem()]
): WordsListBlock {
	return { type: 'list', kind, children };
}

export function createListItem(
	children: readonly WordsInline[] = [createText('')],
	checked = false,
	indent?: number
): WordsListItem {
	return {
		type: 'list-item',
		...(checked ? { checked } : {}),
		...(indent ? { indent } : {}),
		children
	};
}

export function createTable(
	children: readonly WordsTableRow[] = [createTableRow()],
	options: WordsTableOptions = {}
): WordsTableBlock {
	return {
		type: 'table',
		...(options.striped ? { striped: true } : {}),
		...(options.compact ? { compact: true } : {}),
		children
	};
}

export function createTableRow(
	children: readonly WordsTableCell[] = [createTableCell()]
): WordsTableRow {
	return { type: 'table-row', children };
}

export function createTableCell(
	children: readonly WordsInline[] = [createText('')],
	options: WordsTableCellOptions = {}
): WordsTableCell {
	return {
		type: 'table-cell',
		...(options.header ? { header: true } : {}),
		...(options.textAlign && options.textAlign !== 'left' ? { textAlign: options.textAlign } : {}),
		...(options.verticalAlign && options.verticalAlign !== 'top'
			? { verticalAlign: options.verticalAlign }
			: {}),
		...(options.tone && options.tone !== 'default' ? { tone: options.tone } : {}),
		children
	};
}

export function createText(text: string, marks: readonly WordsMark[] = []): WordsText {
	const normalizedMarks = normalizeMarks(marks);
	return {
		type: 'text',
		text,
		...(normalizedMarks.length ? { marks: normalizedMarks } : {})
	};
}

export function createLink(
	href: string,
	children: readonly WordsInline[],
	title?: string
): WordsLink {
	return {
		type: 'link',
		href,
		...(title ? { title } : {}),
		children
	};
}

export function normalizeMarks(marks: readonly WordsMark[] | undefined): readonly WordsMark[] {
	if (!marks?.length) return [];
	const order = new Map<WordsMark, number>(WORDS_MARKS.map((mark, index) => [mark, index]));
	return Array.from(new Set(marks)).sort((a, b) => (order.get(a) ?? 0) - (order.get(b) ?? 0));
}

export function sameMarks(
	a: readonly WordsMark[] | undefined,
	b: readonly WordsMark[] | undefined
): boolean {
	const left = normalizeMarks(a);
	const right = normalizeMarks(b);
	if (left.length !== right.length) return false;
	return left.every((mark, index) => mark === right[index]);
}

export function isWordsMark(value: unknown): value is WordsMark {
	return typeof value === 'string' && (WORDS_MARKS as readonly string[]).includes(value);
}

export function isWordsHeadingLevel(value: unknown): value is WordsHeadingLevel {
	return typeof value === 'number' && (WORDS_HEADING_LEVELS as readonly number[]).includes(value);
}

export function isWordsListKind(value: unknown): value is WordsListKind {
	return typeof value === 'string' && (WORDS_LIST_KINDS as readonly string[]).includes(value);
}

export function isWordsTextAlign(value: unknown): value is WordsTextAlign {
	return typeof value === 'string' && (WORDS_TEXT_ALIGNS as readonly string[]).includes(value);
}

export function isWordsTableCellVerticalAlign(
	value: unknown
): value is WordsTableCellVerticalAlign {
	return (
		typeof value === 'string' &&
		(WORDS_TABLE_CELL_VERTICAL_ALIGNS as readonly string[]).includes(value)
	);
}

export function isWordsTableCellTone(value: unknown): value is WordsTableCellTone {
	return typeof value === 'string' && (WORDS_TABLE_CELL_TONES as readonly string[]).includes(value);
}

export function normalizeWordsCodeLanguage(value: unknown): string | undefined {
	if (typeof value !== 'string') return undefined;
	const language = value.trim().toLowerCase();
	return /^[a-z0-9][a-z0-9+_.-]{0,31}$/.test(language) ? language : undefined;
}

export function isTextInline(inline: WordsInline): inline is WordsText {
	return inline.type === 'text';
}

export function isLinkInline(inline: WordsInline): inline is WordsLink {
	return inline.type === 'link';
}

export function getBlockText(block: WordsBlock): string {
	if (block.type === 'list') {
		return block.children.map((item) => item.children.map(getInlineText).join('')).join('\n');
	}
	if (block.type === 'table') {
		return block.children
			.map((row) =>
				row.children.map((cell) => cell.children.map(getInlineText).join('')).join('\t')
			)
			.join('\n');
	}
	return block.children.map(getInlineText).join('');
}

export function getInlineText(inline: WordsInline): string {
	return getInlineTextSafe(inline, new WeakSet<object>());
}

function getInlineTextSafe(inline: WordsInline, seen: WeakSet<object>): string {
	if (seen.has(inline)) return '';
	seen.add(inline);
	if (inline.type === 'text') return inline.text;
	return inline.children.map((child) => getInlineTextSafe(child, seen)).join('');
}