/**
 * Loading and normalizing the `wechat` section of the shared `bytefly.json`.
 *
 * The effective config is the global section overridden by the project
 * section. Unknown keys are ignored and every value is clamped or cleaned.
 * Connection state is not stored here; the stored account controls the bridge
 * lifecycle.
 */

import { clampInteger, cleanString } from "../../lib/json.ts";
import { loadConfigSection } from "../../lib/config.ts";

export interface WechatConfig {
	/** Turns allowed in a rolling hour; 0 disables the cap. */
	maxTurnsPerHour: number;
	/** Replies longer than this are split into multiple messages. */
	maxReplyChars: number;
	/** Observability identifier sent as `base_info.bot_agent`. */
	botAgent: string;
	/** Plugin version sent as `base_info.channel_version`. */
	channelVersion: string;
	/** Base URL for CDN media downloads and uploads. */
	cdnBaseUrl: string;
	/** Media larger than this is skipped inbound and refused outbound. */
	maxMediaBytes: number;
	/** Inbound files older than this many days are pruned; 0 keeps every one. */
	mediaRetentionDays: number;
	/** Inbound text longer than this is truncated before it reaches the model. */
	maxInboundChars: number;
	/** Send a typing indicator while an inbound turn is being generated. */
	typingIndicator: boolean;
	/**
	 * Ask the server for this long-poll hold, in milliseconds. Unset means "use the
	 * server's own", which is what every release before this option did; the
	 * field is a protocol experiment, so it is opt-in.
	 */
	pollHoldMs?: number;
}

export const DEFAULT_CONFIG: WechatConfig = {
	maxTurnsPerHour: 0,
	maxReplyChars: 4000,
	botAgent: "pi-wechat",
	channelVersion: "0.1.0",
	cdnBaseUrl: "https://novac2c.cdn.weixin.qq.com/c2c",
	maxMediaBytes: 20 * 1024 * 1024,
	mediaRetentionDays: 7,
	maxInboundChars: 8000,
	typingIndicator: true,
};

/** A cleaned, slash-free base URL. */
function toBaseUrl(value: unknown, fallback: string): string {
	return cleanString(value, fallback).replace(/\/+$/, "");
}

/** Validate/clamp a raw config object over a running base. */
export function normalizeConfig(raw: Record<string, unknown> | undefined, base: WechatConfig): WechatConfig {
	const config: WechatConfig = { ...base };
	if (!raw) return config;
	if (raw.maxTurnsPerHour !== undefined) {
		config.maxTurnsPerHour = clampInteger(raw.maxTurnsPerHour, base.maxTurnsPerHour, 0, 500);
	}
	if (raw.maxReplyChars !== undefined) {
		config.maxReplyChars = clampInteger(raw.maxReplyChars, base.maxReplyChars, 1, 20000);
	}
	if (raw.botAgent !== undefined) {
		config.botAgent = cleanString(raw.botAgent, base.botAgent).slice(0, 256);
	}
	if (raw.channelVersion !== undefined) {
		config.channelVersion = cleanString(raw.channelVersion, base.channelVersion);
	}
	if (raw.cdnBaseUrl !== undefined) {
		config.cdnBaseUrl = toBaseUrl(raw.cdnBaseUrl, base.cdnBaseUrl);
	}
	if (raw.maxMediaBytes !== undefined) {
		config.maxMediaBytes = clampInteger(raw.maxMediaBytes, base.maxMediaBytes, 1024, 100 * 1024 * 1024);
	}
	if (raw.mediaRetentionDays !== undefined) {
		config.mediaRetentionDays = clampInteger(raw.mediaRetentionDays, base.mediaRetentionDays, 0, 3650);
	}
	if (raw.maxInboundChars !== undefined) {
		config.maxInboundChars = clampInteger(raw.maxInboundChars, base.maxInboundChars, 1000, 100_000);
	}
	if (typeof raw.typingIndicator === "boolean") {
		config.typingIndicator = raw.typingIndicator;
	}
	if (raw.pollHoldMs !== undefined) {
		// A malformed value keeps an inherited hold, as every sibling field does; only a
		// numeric `0` clears it.
		const hold = clampInteger(raw.pollHoldMs, base.pollHoldMs ?? 0, 0, 120_000);
		config.pollHoldMs = hold >= 1000 ? hold : undefined;
	}
	return config;
}

/** The effective config from the shared `wechat` section. */
export function loadWechatConfig(cwd: string): WechatConfig {
	return loadConfigSection(cwd, "wechat", DEFAULT_CONFIG, normalizeConfig);
}