import { createHash } from "node:crypto";
import type { AssistantMessage, Context, Message } from "@earendil-works/pi-ai";
import { isRecord } from "./types.js";

function contentToText(content: unknown): string {
	if (typeof content === "string") return content;
	if (!Array.isArray(content)) return "";
	return content
		.map((block) => {
			if (!isRecord(block)) return "";
			if (block.type === "text" && typeof block.text === "string") return block.text;
			if (block.type === "image") return "[image omitted: Grok Build ACP text provider]";
			if (block.type === "toolCall") {
				return `[Pi tool call: ${String(block.name ?? "unknown")} ${JSON.stringify(block.arguments ?? {})}]`;
			}
			return "";
		})
		.filter((part) => part.length > 0)
		.join("\n");
}

function messageText(message: Message): string {
	return contentToText(message.content);
}

function toolName(message: Message): string {
	return "toolName" in message && typeof message.toolName === "string" ? message.toolName : "tool";
}

export function buildFullPrompt(context: Context): string {
	const parts: string[] = [];
	if (context.systemPrompt?.trim()) parts.push(`system:\n${context.systemPrompt.trim()}`);
	for (const message of context.messages) {
		const text = messageText(message);
		if (message.role === "user") parts.push(`user:\n${text}`);
		else if (message.role === "assistant") parts.push(`assistant:\n${text}`);
		else if (message.role === "toolResult") parts.push(`tool result (${toolName(message)}):\n${text}`);
	}
	return parts.filter((part) => part.trim().length > 0).join("\n\n");
}

export function buildIncrementalPrompt(context: Context): string {
	let lastAssistant = -1;
	for (let index = context.messages.length - 1; index >= 0; index--) {
		if (context.messages[index]?.role === "assistant") {
			lastAssistant = index;
			break;
		}
	}
	const parts: string[] = [];
	for (const message of context.messages.slice(lastAssistant + 1)) {
		const text = messageText(message);
		if (message.role === "user") parts.push(text);
		else if (message.role === "toolResult") parts.push(`tool result (${toolName(message)}):\n${text}`);
	}
	return parts.filter((part) => part.trim().length > 0).join("\n\n") || buildFullPrompt(context);
}

export function fingerprintMessages(messages: readonly Message[]): string {
	const hash = createHash("sha256");
	for (const message of messages) {
		hash.update(message.role);
		hash.update("\0");
		hash.update(messageText(message));
		hash.update("\0");
	}
	return hash.digest("hex");
}

export function currentAssistantPrefixFingerprint(context: Context): string | undefined {
	let lastAssistant = -1;
	for (let index = context.messages.length - 1; index >= 0; index--) {
		if (context.messages[index]?.role === "assistant") {
			lastAssistant = index;
			break;
		}
	}
	return lastAssistant >= 0 ? fingerprintMessages(context.messages.slice(0, lastAssistant + 1)) : undefined;
}

export function expectedNextPrefixFingerprint(context: Context, output: AssistantMessage): string {
	return fingerprintMessages([...context.messages, output]);
}