/**
 * setBlockVisual — merges common style props into a block.
 *
 * The common style properties (`align`, `margin`, `padding`,
 * `background`, `color`, `border`) live on the base `Block`, so every
 * block accepts any of them — no per-type whitelist. `undefined`
 * clears a property; a patch that changes nothing is a no-op.
 */

import { normalizeDocument } from './normalize';
import { getNodeAtPath, updateNodeAtPath } from './helpers';
import { changed, noOp, type WordsEditorState, type WordsOperationResult } from './types';
import type { WordsPath } from '../path';
import type { Block, WordsBlock } from '../types';

/**
 * A node accepts the common `Block` style props (margin / padding /
 * color / border / …) when it EXTENDS `Block`. That is every block
 * (paragraph, heading, …) AND every structural Block-subtype that has
 * no `type` discriminator: `Column`, `TableRow`, `TableCell`,
 * `ListItem`. It is NOT the document and NOT an inline (`text` / `link`,
 * which carry a `type` but are not `Block`s).
 *
 * The earlier guard tested `'type' in target`, which was exactly
 * backwards: it let inlines through (they have a `type`) and rejected
 * columns / rows / cells (they don't). Those structural nodes are the
 * whole point — a column carries its own background / padding / border.
 */
function isBlockLikeTarget(target: unknown): boolean {
	if (!target || typeof target !== 'object') return false;
	if ('version' in target) return false; // document root
	const t = (target as { type?: string }).type;
	if (t === 'text' || t === 'link') return false; // inline
	return true; // block OR column / table-row / table-cell / list-item
}

const STYLE_KEYS = [
	'align',
	'margin',
	'padding',
	'background',
	'color',
	'border',
	'fontSize',
	'fontFamily',
	'fontWeight',
	'lineHeight',
	'fontStyle',
	'strikethrough',
	'letterSpacing',
	'wordSpacing',
	'textWrap',
	'maxWidth',
	'tabularNumbers'
] as const;

export function setBlockVisual(
	state: WordsEditorState,
	blockIndex: number,
	patch: Partial<Block>
): WordsOperationResult {
	const block = state.document.children[blockIndex];
	if (!block) return noOp(state);

	const prev = block as unknown as Record<string, unknown>;
	const next: Record<string, unknown> = { ...prev };
	let touched = false;
	for (const key of STYLE_KEYS) {
		if (!(key in patch)) continue;
		const value = (patch as Record<string, unknown>)[key];
		if (value === undefined) {
			if (key in next) {
				delete next[key];
				touched = true;
			}
		} else if (!styleEqual(next[key], value)) {
			next[key] = value;
			touched = true;
		}
	}
	if (!touched) return noOp(state);

	const nextDoc = normalizeDocument({
		...state.document,
		children: replaceAt(state.document.children, blockIndex, next as unknown as WordsBlock)
	}).document;
	return changed({ ...state, document: nextDoc });
}

/**
 * Path-aware twin of `setBlockVisual`. Walks `blockPath` to find the
 * target block (top-level OR nested inside `columns` / `callout`) and
 * applies the same style-merge semantics. Used by the inspector when
 * the user has clicked into a block nested inside a column — the
 * top-level `blockIndex` would point at the wrapper, so the path
 * version is the only way to touch the right block.
 */
export function setBlockVisualAtPath(
	state: WordsEditorState,
	blockPath: WordsPath,
	patch: Partial<Block>
): WordsOperationResult {
	if (blockPath.length === 0) return noOp(state);
	const target = getNodeAtPath(state.document, blockPath);
	if (!isBlockLikeTarget(target)) return noOp(state);

	const prev = target as unknown as Record<string, unknown>;
	const next: Record<string, unknown> = { ...prev };
	let touched = false;
	for (const key of STYLE_KEYS) {
		if (!(key in patch)) continue;
		const value = (patch as Record<string, unknown>)[key];
		if (value === undefined) {
			if (key in next) {
				delete next[key];
				touched = true;
			}
		} else if (!styleEqual(next[key], value)) {
			next[key] = value;
			touched = true;
		}
	}
	if (!touched) return noOp(state);

	const nextDoc = updateNodeAtPath(state.document, blockPath, () => next as unknown as WordsBlock);
	if (nextDoc === state.document) return noOp(state);
	const normalized = normalizeDocument(nextDoc).document;
	return changed({ ...state, document: normalized });
}

/**
 * Path-aware shallow merge — mirrors `updateBlockAt` but accepts a full
 * document path. Used by the inspector's Block panel (alt / caption /
 * src / column children…) when the target block sits inside a column.
 * Preserves the block's discriminator (`type` is filtered out of the
 * patch, same as the top-level op).
 */
export function updateBlockAtPath(
	state: WordsEditorState,
	blockPath: WordsPath,
	patch: Readonly<Record<string, unknown>>
): WordsOperationResult {
	if (blockPath.length === 0) return noOp(state);
	const target = getNodeAtPath(state.document, blockPath);
	if (!isBlockLikeTarget(target)) return noOp(state);

	const safePatch: Record<string, unknown> = {};
	for (const [k, v] of Object.entries(patch)) {
		if (k === 'type') continue;
		safePatch[k] = v;
	}

	const nextDoc = updateNodeAtPath(
		state.document,
		blockPath,
		(node) =>
			({
				...(node as unknown as Record<string, unknown>),
				...safePatch
			}) as unknown as WordsBlock
	);
	if (nextDoc === state.document) return noOp(state);
	const normalized = normalizeDocument(nextDoc).document;
	return changed({ ...state, document: normalized });
}

// ── Helpers ──────────────────────────────────────────────────────────────

/** Shallow equality, descending one level into the small style objects
 *  (`margin` / `padding` / `border`). */
function styleEqual(a: unknown, b: unknown): boolean {
	if (a === b) return true;
	if (typeof a === 'object' && a !== null && typeof b === 'object' && b !== null) {
		const ao = a as Record<string, unknown>;
		const bo = b as Record<string, unknown>;
		const ak = Object.keys(ao);
		const bk = Object.keys(bo);
		if (ak.length !== bk.length) return false;
		return ak.every((k) => ao[k] === bo[k]);
	}
	return false;
}

function replaceAt<T>(arr: readonly T[], index: number, value: T): readonly T[] {
	return [...arr.slice(0, index), value, ...arr.slice(index + 1)];
}