import { debugLog } from "./debug.ts";

import type { ExtensionContext } from "@earendil-works/pi-coding-agent";
export type EditorFactory = NonNullable<ReturnType<ExtensionContext["ui"]["getEditorComponent"]>>;
export interface EditorHost {
	getEditorComponent?(): EditorFactory | undefined;
	setEditorComponent?(factory: EditorFactory | undefined): void;
}

/** Owns composition and restoration without leaking stale session contexts. */
export class PiEditorAdapter {
	private installed?: EditorFactory;
	private previous?: EditorFactory;
	private previousFailed = false;
	private redraw?: () => void;

	install(ui: EditorHost, create: (...args: [...Parameters<EditorFactory>, ReturnType<EditorFactory>?]) => ReturnType<EditorFactory>): void {
		const current = ui.getEditorComponent?.();
		if (current !== this.installed) {
			this.previous = current;
			this.previousFailed = false;
		}
		const previous = this.previous;
		this.installed = (tui, theme, keys) => {
			let base: ReturnType<EditorFactory> | undefined;
			try { base = previous?.(tui, theme, keys); }
			catch (error) {
				debugLog("Displaced editor factory failed; building a standalone editor", error);
				this.previousFailed = true;
			}
			const editor = create(tui, theme, keys, base);
			this.redraw = () => { editor.invalidate?.(); tui.requestRender(); };
			return editor;
		};
		for (const name of ["pi-zentui.editor-factory", "pi-zentui.editor-owner", "pi-zentui.editor-base-factory"]) {
			const symbol = Symbol.for(name);
			// SAFETY: foreign editor factories use these symbol properties as ownership metadata.
			const value = previous ? (previous as unknown as Record<symbol, unknown>)[symbol] : undefined;
			if (value !== undefined) Object.defineProperty(this.installed, symbol, { value });
		}
		ui.setEditorComponent?.(this.installed);
	}

	refresh(): void {
		try { this.redraw?.(); }
		catch (error) { debugLog("Draft editor redraw failed", error); }
	}

	dispose(ui: EditorHost): void {
		const installed = this.installed;
		// SAFETY: Zentui marks its factory with this shared ownership symbol.
		const isZentui = Boolean(this.previous && (this.previous as unknown as Record<symbol, unknown>)[Symbol.for("pi-zentui.editor-factory")]);
		const previous = isZentui || this.previousFailed ? undefined : this.previous;
		const restore = (): void => {
			try { ui.setEditorComponent?.(previous); }
			catch (error) {
				debugLog("Restoring the displaced editor failed; clearing it", error);
				try { ui.setEditorComponent?.(undefined); } catch { /* disposed UI */ }
			}
		};
		if (installed && ui.getEditorComponent?.() === installed) restore();
		else if (installed) {
			const timer = setTimeout(() => {
				try { if (ui.getEditorComponent?.() === installed) restore(); } catch { /* disposed UI */ }
			}, 0);
			timer.unref?.();
		}
		this.installed = this.previous = undefined;
		this.previousFailed = false;
		this.redraw = undefined;
	}
}