/**
 * Prompt Section Registry — manages ordered prompt sections with sources,
 * budgets, and trim states.
 *
 * The registry collects prompt sections from multiple data sources (kernel
 * snapshots, facts, evidence, gate decisions, etc.), enforces per-section
 * and global budgets, and produces a final PromptContract.
 *
 * Sections are ordered by priority (lower number = higher priority = trimmed
 * last).  Sections marked `always: true` are never trimmed regardless of
 * budget pressure.
 */

import type {
	CompileContext,
	PromptContract,
	PromptSection,
	PromptSectionSource,
	TrimLogEntry,
} from "./prompt-contract.ts";
import { assembleContract, enforceBudgets } from "./prompt-contract.ts";
import type { KernelSnapshot, EvidenceSummary } from "../kernel/snapshots.ts";
import type { GateResult, KdFact, KdToolResultContract, KdWorkingSet } from "../types.ts";

// ── PromptSectionRegistry ────────────────────────────────────────────

/**
 * Registry that collects, orders, and trims prompt sections.
 *
 * Usage:
 * ```ts
 * const registry = new PromptSectionRegistry();
 * registry.register({ id: "control", title: "Control Frame", ... });
 * registry.register({ id: "facts", title: "Facts", ... });
 * const contract = registry.compile(context);
 * ```
 */
export class PromptSectionRegistry {
	private sections: PromptSection[] = [];

	/**
	 * Register a prompt section.
	 *
	 * If a section with the same `id` already exists, it is replaced.
	 * The replacement preserves insertion order (the new section takes the
	 * position of the old one).
	 */
	register(section: PromptSection): void {
		const existingIndex = this.sections.findIndex((s) => s.id === section.id);
		if (existingIndex >= 0) {
			this.sections[existingIndex] = section;
		} else {
			this.sections.push(section);
		}
	}

	/**
	 * Compile all registered sections into a PromptContract.
	 *
	 * Steps:
	 * 1. Filter out sections with `include: false` or empty content (unless `always: true`)
	 * 2. Sort by priority (ascending — lower = higher priority)
	 * 3. Enforce per-section budgets, then global budget
	 * 4. Assemble the final contract
	 */
	compile(context: CompileContext): PromptContract {
		// Filter: include !== false, and either always or has meaningful content
		const eligible = this.sections.filter(
			(section) => section.include !== false && (section.always || hasMeaningfulContent(section.content)),
		);

		// Sort by priority ascending (lower number = higher priority = trimmed last)
		const sorted = [...eligible].sort((a, b) => a.priority - b.priority);

		// Enforce budgets
		const { sections: trimmed, trimLog } = enforceBudgets(sorted, context.totalBudget);

		// Assemble contract
		const contract = assembleContract(trimmed, context.totalBudget);
		return {
			...contract,
			trimLog,
		};
	}

	/**
	 * Return all sections marked as uncuttable (`always: true`).
	 */
	getUntrimmables(): PromptSection[] {
		return this.sections.filter((s) => s.always);
	}

	/**
	 * Return the current count of registered sections.
	 */
	get size(): number {
		return this.sections.length;
	}

	/**
	 * Clear all registered sections.
	 */
	clear(): void {
		this.sections = [];
	}
}

// ── Section factory helpers ──────────────────────────────────────────

/**
 * Create a prompt section from a kernel snapshot.
 *
 * Produces a compact status summary suitable for the "status" section
 * of the prompt contract.
 */
export function sectionFromKernelSnapshot(snapshot: KernelSnapshot): PromptSection {
	const content = [
		`Run：${snapshot.runId}`,
		`状态：${snapshot.runStatus}`,
		`阶段/模式：${snapshot.phase}/${snapshot.mode}`,
		snapshot.product ? `产品：${snapshot.product}` : undefined,
		`事实：${snapshot.factsSummary.current} current / ${snapshot.factsSummary.total} total`,
		`未回答问题：${snapshot.openQuestionsCount}`,
		`门禁：${snapshot.gateResult.passed ? "通过" : `阻塞：${snapshot.gateResult.reason ?? "未说明原因"}`}`,
		`证据：${snapshot.evidenceSummary.total} entries (${snapshot.evidenceSummary.kinds.join(", ")})`,
		`生成时间：${snapshot.generatedAt}`,
	]
		.filter(Boolean)
		.join("\n");

	return {
		id: "kernel-snapshot",
		title: "Kernel Snapshot（运行状态快照）",
		content,
		source: "kernel-snapshot",
		priority: 10,
		always: true,
		include: true,
		traceId: `snapshot-${snapshot.runId}-${snapshot.generatedAt}`,
	};
}

/**
 * Create a prompt section from gate decisions.
 */
export function sectionFromGateDecisions(gates: GateResult[], runId: string): PromptSection {
	if (gates.length === 0) {
		return {
			id: "gate-decisions",
			title: "门禁决策记录",
			content: "无门禁决策。",
			source: "gate-decision",
			priority: 20,
			always: false,
			include: false,
			traceId: `gates-${runId}-empty`,
		};
	}

	const content = gates
		.map((gate, i) => {
			const status = gate.passed ? "通过" : "阻塞";
			const reason = gate.reason ? `：${gate.reason}` : "";
			return `- [${i + 1}] ${status}${reason} (${gate.checkedAt})`;
		})
		.join("\n");

	return {
		id: "gate-decisions",
		title: "门禁决策记录",
		content,
		source: "gate-decision",
		priority: 20,
		always: false,
		include: true,
		traceId: `gates-${runId}`,
	};
}

/**
 * Create a prompt section from facts.
 */
export function sectionFromFacts(facts: KdFact[], runId: string): PromptSection {
	const currentFacts = facts.filter((f) => f.status === "current");

	if (currentFacts.length === 0) {
		return {
			id: "facts",
			title: "结构化事实",
			content: "无当前事实。",
			source: "facts",
			priority: 30,
			always: false,
			include: false,
			traceId: `facts-${runId}-empty`,
		};
	}

	const content = currentFacts
		.map((fact) => `- **${fact.label}**（${fact.key}）：${fact.value}`)
		.join("\n");

	return {
		id: "facts",
		title: "结构化事实",
		content,
		source: "facts",
		priority: 30,
		always: false,
		include: true,
		traceId: `facts-${runId}`,
	};
}

/**
 * Create a prompt section from evidence summary.
 */
export function sectionFromEvidence(evidence: EvidenceSummary, runId: string): PromptSection {
	if (evidence.total === 0) {
		return {
			id: "evidence",
			title: "证据摘要",
			content: "无证据。",
			source: "evidence",
			priority: 40,
			always: false,
			include: false,
			traceId: `evidence-${runId}-empty`,
		};
	}

	const content = [
		`证据总数：${evidence.total}`,
		`类型：${evidence.kinds.join(", ")}`,
		`来源信任分布：${Object.entries(evidence.sourceTrust).map(([k, v]) => `${k}=${v}`).join(", ")}`,
	].join("\n");

	return {
		id: "evidence",
		title: "证据摘要",
		content,
		source: "evidence",
		priority: 40,
		always: false,
		include: true,
		traceId: `evidence-${runId}`,
	};
}

/**
 * Create a prompt section from tool results.
 */
export function sectionFromToolResults(results: KdToolResultContract[], runId: string): PromptSection {
	if (results.length === 0) {
		return {
			id: "tool-results",
			title: "工具结果",
			content: "无工具结果。",
			source: "tool-result",
			priority: 50,
			always: false,
			include: false,
			traceId: `tools-${runId}-empty`,
		};
	}

	const content = results
		.slice(-14)
		.map((r) => `- [${r.status}] ${r.toolName}（${r.kind}）：${r.summary}`)
		.join("\n");

	return {
		id: "tool-results",
		title: "工具结果",
		content,
		source: "tool-result",
		priority: 50,
		always: false,
		include: true,
		traceId: `tools-${runId}`,
	};
}

/**
 * Create a prompt section from working set.
 */
export function sectionFromWorkingSet(workingSet: KdWorkingSet | undefined, runId: string): PromptSection {
	if (!workingSet) {
		return {
			id: "working-set",
			title: "工作集",
			content: "无工作集。",
			source: "working-set",
			priority: 60,
			always: false,
			include: false,
			traceId: `ws-${runId}-empty`,
		};
	}

	const content = [
		`焦点：${workingSet.focus}`,
		workingSet.activeGap ? `活跃缺口：${workingSet.activeGap}` : undefined,
		workingSet.currentAction ? `当前动作：${workingSet.currentAction}` : undefined,
		workingSet.blockedBy ? `阻塞于：${workingSet.blockedBy}` : undefined,
		`近期文件：${workingSet.recentFiles.map((f) => f.path).join(", ") || "无"}`,
		`禁止漂移：${workingSet.forbiddenDrift.join(", ") || "无"}`,
	]
		.filter(Boolean)
		.join("\n");

	return {
		id: "working-set",
		title: "工作集",
		content,
		source: "working-set",
		priority: 60,
		always: false,
		include: true,
		traceId: `ws-${runId}`,
	};
}

/**
 * Create a prompt section from user input.
 */
export function sectionFromUserInput(userInput: string, runId: string): PromptSection {
	return {
		id: "user-input",
		title: "用户本轮输入",
		content: userInput,
		source: "user-input",
		priority: 5,
		always: true,
		include: true,
		traceId: `input-${runId}-${Date.now()}`,
	};
}

// ── Internal helpers ─────────────────────────────────────────────────

/**
 * Check whether content is meaningful (not empty, not a placeholder).
 */
function hasMeaningfulContent(content: string): boolean {
	const trimmed = content.trim();
	return Boolean(trimmed && trimmed !== "无。" && trimmed !== "无。" && !/^无[^。]*。$/.test(trimmed));
}