import { CustomEditor, type ExtensionAPI } from "@earendil-works/pi-coding-agent";
import type { Component, OverlayHandle, TUI } from "@earendil-works/pi-tui";

/** Menu desenhado pelo TUI como camada flutuante, fora do fluxo do Editor. */
class AutocompleteOverlay implements Component {
	lines: string[] = [];

	render(width: number): string[] {
		return this.lines.map((line) => line.slice(0, width));
	}

	invalidate(): void {}
}

/**
 * Mantém o autocomplete nativo (filtro, seleção e atalhos), mas extrai suas
 * linhas do Editor e as apresenta em um overlay acima da caixa de entrada.
 */
class AutocompleteOverlayEditor extends CustomEditor {
	private readonly hostTui: TUI;
	private overlay?: AutocompleteOverlay;
	private overlayHandle?: OverlayHandle;
	private overlayBottomMargin?: number;

	constructor(...args: ConstructorParameters<typeof CustomEditor>) {
		super(...args);
		this.hostTui = args[0];
	}

	render(width: number): string[] {
		const lines = super.render(width);
		const internals = this as unknown as {
			autocompleteState: unknown | null;
			autocompleteList?: { render(width: number): string[] };
			paddingX: number;
		};

		if (!internals.autocompleteState || !internals.autocompleteList) {
			this.hideAutocompleteOverlay();
			return lines;
		}

		const maxPadding = Math.max(0, Math.floor((width - 1) / 2));
		const paddingX = Math.min(internals.paddingX, maxPadding);
		const contentWidth = Math.max(1, width - paddingX * 2);
		const menuHeight = internals.autocompleteList.render(contentWidth).length;

		if (menuHeight <= 0 || menuHeight >= lines.length) {
			this.hideAutocompleteOverlay();
			return lines;
		}

		const editorHeight = lines.length - menuHeight;
		const editorLines = lines.slice(0, editorHeight);
		const menuLines = lines.slice(editorHeight);

		// O anchor bottom-left é relativo ao terminal inteiro. Além da altura do
		// Editor, reservamos a linha do footer para o menu terminar exatamente
		// na borda superior da caixa de entrada, sem cobri-la.
		this.showAutocompleteOverlay(menuLines, editorHeight + 1);
		return editorLines;
	}

	dispose(): void {
		this.overlayHandle?.hide();
		this.overlayHandle = undefined;
		this.overlay = undefined;
	}

	private showAutocompleteOverlay(lines: string[], bottomMargin: number): void {
		// O tamanho do Editor pode variar se a mensagem tiver várias linhas.
		// Nesse caso, recriamos o overlay na nova posição.
		if (this.overlayHandle && this.overlayBottomMargin !== bottomMargin) {
			this.overlayHandle.hide();
			this.overlayHandle = undefined;
			this.overlay = undefined;
		}

		if (!this.overlay || !this.overlayHandle) {
			this.overlay = new AutocompleteOverlay();
			this.overlayBottomMargin = bottomMargin;
			this.overlayHandle = this.hostTui.showOverlay(this.overlay, {
				anchor: "bottom-left",
				width: "100%",
				margin: { bottom: bottomMargin },
				nonCapturing: true,
			});
		}

		this.overlay.lines = lines;
		this.overlayHandle.setHidden(false);
	}

	private hideAutocompleteOverlay(): void {
		if (this.overlayHandle && !this.overlayHandle.isHidden()) {
			this.overlayHandle.setHidden(true);
		}
	}
}

export default function autocompleteOverlay(pi: ExtensionAPI) {
	let editor: AutocompleteOverlayEditor | undefined;

	pi.on("session_start", (_event, ctx) => {
		if (ctx.mode !== "tui") return;
		ctx.ui.setEditorComponent((tui, theme, keybindings) => {
			editor = new AutocompleteOverlayEditor(tui, theme, keybindings);
			return editor;
		});
	});

	pi.on("session_shutdown", () => {
		editor?.dispose();
		editor = undefined;
	});
}