/**
 * Session → markdown — the ONE formatting engine (owner ruling 2026-09-27).
 *
 * The extractor's view of a teaching session and the future user-facing
 * session export share this engine: a session is rendered as clean,
 * readable markdown — speaker headers, quiz/check-in blocks, tool notes —
 * with optional message-id anchors. Since the submit-schema slim
 * (2026-09-28) propositions no longer report message ids — the extractor
 * renders anchorless and provenance is chat-level — so the anchors today
 * serve only the future user-facing export; `anchors: false` mints the
 * same document without them.
 *
 * Pure core: native messages in (LhMessage), string out. Content parity
 * with the coverage line builder (core/coverage.ts messageViewLines) is
 * deliberate — every message that produces view lines produces a markdown
 * block, in the same order — but the formats are SEPARATE by design
 * (2026-09-27): coverage fingerprints hash the line format and stay stable
 * (no mass re-extraction when presentation changes); markdown is
 * presentation. A failed tool call renders nothing (retry context, not
 * learning evidence); custom markers are invisible, same as the view.
 */

import type { LhMessage } from "./native-messages.ts";
import type { ToolResultMessage } from "@earendil-works/pi-ai";

/** The user-facing text blocks of a native message (string or text parts). */
function textOf(content: unknown): string[] {
	if (typeof content === "string") return content.trim() ? [content] : [];
	if (!Array.isArray(content)) return [];
	return content
		.filter((c): c is { type: "text"; text: string } => (c as { type?: string }).type === "text")
		.map((c) => c.text)
		.filter((t) => t.trim().length > 0);
}

/** One tool result's learner-visible outcome, rendered as body lines. */
function toolResultBody(result: ToolResultMessage): { heading: string; body: string[] } {
	const out = result.details as
		| Partial<{
				questionText: string;
				correct: boolean;
				dontKnow: boolean;
				note: string;
				text: string;
				answers: string[];
				other: string;
				dismissed: boolean;
		  }>
		| undefined;

	if (result.toolName === "quiz" || result.toolName === "explain") {
		const heading = result.toolName === "quiz" ? "Quiz" : "Recall check";
		const question = typeof out?.questionText === "string" && out.questionText ? out.questionText : "(no question text)";
		const body = [`**Q:** ${question}`];
		if (out?.dismissed === true) body.push("The learner skipped this check.");
		else if (out?.dontKnow === true) body.push("The learner did not know.");
		else if (out?.correct === true) body.push("The learner answered correctly.");
		else if (out?.correct === false) body.push("The learner answered incorrectly.");
		else if (typeof out?.text === "string" && out.text.trim()) body.push(`The learner answered in his own words: ${out.text.trim()}`);
		if (typeof out?.note === "string" && out.note) body.push(`*(his thinking: ${out.note})*`);
		return { heading, body };
	}

	if (result.toolName === "ask_user_question") {
		const question = typeof out?.questionText === "string" && out.questionText ? out.questionText : "(no question text)";
		const body = [`**Q:** ${question}`];
		const chosen = [
			...(Array.isArray(out?.answers) ? out!.answers! : []),
			...(typeof out?.other === "string" && out.other.trim() ? [out.other.trim()] : []),
		];
		if (typeof out?.text === "string" && out.text.trim()) body.push(`The learner answered: ${out.text.trim()}`);
		else if (chosen.length > 0) body.push(`The learner chose: ${chosen.join(", ")}`);
		else if (out?.dismissed === true) body.push("The learner skipped this question.");
		if (typeof out?.note === "string" && out.note) body.push(`*(his thinking: ${out.note})*`);
		return { heading: "Question", body };
	}

	// Parity with the line builder: other clean tool results are one line.
	return { heading: "Tool", body: [`*${result.toolName} result delivered*`] };
}

/**
 * ONE message as a markdown block — `null` when the message renders
 * nothing (a failed tool call, a bare marker, an empty text part set).
 * `mid` is the provenance anchor shown when `anchors` is on.
 */
export function messageMarkdown(message: LhMessage, mid: string, anchors = true): string | null {
	const role = (message as { role?: string }).role;
	const anchor = anchors ? ` · ${mid}` : "";
	const parts: string[] = [];

	if (role === "user") {
		for (const text of textOf((message as { content: unknown }).content)) {
			parts.push(`### Learner${anchor}\n\n${text.trim()}`);
		}
	} else if (role === "assistant") {
		for (const text of textOf((message as { content: unknown }).content)) {
			parts.push(`### Teacher${anchor}\n\n${text.trim()}`);
		}
	} else if (role === "toolResult") {
		const result = message as ToolResultMessage;
		if (result.isError) return null; // retry context, not learning evidence
		const { heading, body } = toolResultBody(result);
		parts.push(`### ${heading}${anchor}\n\n${body.join("\n\n")}`);
	}

	// custom markers are invisible, same as the extraction view.
	return parts.length > 0 ? parts.join("\n\n") : null;
}

/**
 * A whole session (or one extraction BATCH — same engine, subset of
 * messages) as one markdown document. Blocks render in message order;
 * messages that render nothing are skipped silently. The optional title
 * mints the document header (`# <title>`).
 */
export function sessionMarkdown(
	messages: ReadonlyArray<LhMessage>,
	opts: { title?: string; anchors?: boolean } = {},
): string {
	const blocks: string[] = [];
	if (opts.title !== undefined && opts.title.length > 0) blocks.push(`# ${opts.title}`);
	for (const message of messages) {
		const block = messageMarkdown(message, (message as { id?: string }).id ?? "", opts.anchors ?? true);
		if (block !== null) blocks.push(block);
	}
	return blocks.join("\n\n");
}