export const WORDS_DOCUMENT_VERSION = 1;

/**
 * Inline mark — boolean format flags ('bold', 'italic', ...) plus
 * parametric marks carrying a value via colon-prefixed syntax:
 *   - `color:#ff0000`     foreground text color (hex with #)
 *   - `bgcolor:#ffeeaa`   highlight / background color
 *
 * Parametric marks REPLACE same-prefix entries when toggled (you
 * can have at most one of each prefix per inline). The HTML
 * serializer emits them as `style="color:..; background-color:..."`.
 * Boolean marks toggle as before.
 */
export type WordsMark =
	| 'bold'
	| 'italic'
	| 'underline'
	| 'strike'
	| 'code'
	| `color:${string}`
	| `bgcolor:${string}`;
export type WordsBlockType =
	| 'paragraph'
	| 'heading'
	| 'quote'
	| 'code'
	| 'list'
	| 'table'
	| 'image';
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
};

// Image types live in the image extension (F3). Re-exported here for
// the same reason as the table types — keep `engine/document` as the
// historical import surface working while new code uses
// `extensions/image` directly.
import type {
	WordsImageAlign,
	WordsImageBlock,
	WordsImageOptions,
	WordsImageStatus
} from '../extensions/image/types';
export type {
	WordsImageAlign,
	WordsImageBlock,
	WordsImageOptions,
	WordsImageStatus
};

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

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

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[];
// Table cell value-set constants live in the table extension since
// F2.3b. Re-exported here for backward compat with consumers that
// import them from `engine/document`.
export {
	WORDS_TABLE_CELL_VERTICAL_ALIGNS,
	WORDS_TABLE_CELL_TONES
} from '../extensions/table/factories';

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
	};
}

// Table factory functions live in the table extension since F2.3b.
// Re-exported here for backward compat — see `extensions/table/factories.ts`.
export { createTable, createTableRow, createTableCell } from '../extensions/table/factories';

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<string, number>(
		(WORDS_MARKS as readonly string[]).map((mark, index) => [mark, index])
	);
	// Dedupe boolean marks; for parametric marks (color:X, bgcolor:Y)
	// keep only the LAST value per prefix so multiple toggles in a
	// row resolve to the user's final choice.
	const seenPrefix = new Map<string, WordsMark>();
	const booleanSet = new Set<WordsMark>();
	for (const mark of marks) {
		const colon = mark.indexOf(':');
		if (colon > 0) {
			seenPrefix.set(mark.slice(0, colon), mark);
		} else {
			booleanSet.add(mark);
		}
	}
	const dedup = [...booleanSet, ...seenPrefix.values()];
	// Sort: boolean marks first in declaration order, parametric marks
	// after (stable). This keeps existing tests happy.
	return dedup.sort((a, b) => {
		const ai = order.get(a) ?? 1e6;
		const bi = order.get(b) ?? 1e6;
		return ai - bi;
	});
}

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 {
	if (typeof value !== 'string') return false;
	if ((WORDS_MARKS as readonly string[]).includes(value)) return true;
	// Parametric: `color:#hex` or `bgcolor:#hex`. Liberal hex check —
	// anything that's `#` + 3/4/6/8 hex digits.
	const colorMatch = value.match(/^(color|bgcolor):(#[0-9a-fA-F]{3,8})$/);
	return !!colorMatch;
}

/**
 * Read the parametric value carried by a mark, or undefined for
 * boolean marks. Returns the part after the colon.
 *
 *   markValue('color:#ff0000')   // '#ff0000'
 *   markValue('bold')            // undefined
 */
export function markValue(mark: WordsMark): string | undefined {
	const colon = mark.indexOf(':');
	return colon > 0 ? mark.slice(colon + 1) : undefined;
}

/** Prefix of a parametric mark, or the mark itself for boolean ones. */
export function markPrefix(mark: WordsMark): string {
	const colon = mark.indexOf(':');
	return colon > 0 ? mark.slice(0, colon) : mark;
}

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);
}

// Table predicates live in the table extension since F2.3b.
// Re-exported here for backward compat.
export {
	isWordsTableCellVerticalAlign,
	isWordsTableCellTone
} from '../extensions/table/factories';

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');
	}
	if (block.type === 'image') {
		// Plain-text representation of an image is its alt text. Used
		// for word count, copy-as-plaintext and accessibility flows.
		// Captions are *not* included to keep the image a single
		// semantic atom in plain-text contexts.
		return block.alt ?? '';
	}
	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('');
}