const fs = require("fs");
const path = require("path");
const { SearchProvider } = require("./provider_adapter");
const { formatResults, normalizeOrigin } = require("./result_formatter");
const { readSettings } = require("./settings");
const { evaluateUrl } = require("./url_policy");

class WebSearchTool {
  constructor(options = {}) {
    this.dataDir = options.dataDir;
    this.provider = options.provider || new SearchProvider(options);
    this.now = options.now || Date.now;
    this.cache = new Map();
    this.rateLimits = new Map();
  }

  async run(input = {}) {
    const started = this.now();
    const settings = readSettings(this.dataDir);
    const query = String(input.query || "").trim().slice(0, 500);
    const reason = String(input.reason || "general_lookup");
    const origin = trustedOrigin(input.ctx, input.origin);
    const actor = String(input.user?.id || input.user?.username || "unknown").slice(0, 120);
    const server = String(input.ctx?.server_id || input.ctx?.channel_id || "direct").slice(0, 120);
    const auditBase = { query, reason, origin, actor, server };
    if (!settings.enabled) return this.finish(blockedResult(query, reason, "tool_disabled", settings, started, this.now()), auditBase);
    if (!settings.allowed_origins.includes(origin)) {
      return this.finish(blockedResult(query, reason, "origin_not_allowed", settings, started, this.now()), auditBase);
    }
    if (!query) return this.finish(blockedResult(query, reason, "query_required", settings, started, this.now()), auditBase);
    if (!this.consumeRateLimit(`${origin}:${server}:${actor}`, settings.requests_per_minute)) {
      return this.finish(blockedResult(query, reason, "rate_limited", settings, started, this.now()), auditBase);
    }
    const cacheKey = JSON.stringify([
      query.toLowerCase(), reason, input.freshness || "", settings.provider_endpoint,
      settings.policy_mode, settings.url_rules, settings.safe_search, settings.max_results,
      origin, settings[`${origin}_output_chars`], settings.show_source_links,
      input.requested_depth || "search", settings.allow_full_page_fetch
    ]);
    const cached = this.cache.get(cacheKey);
    if (cached && cached.expiresAt > this.now()) {
      return this.finish({ ...cached.value, cache_hit: true, timing_ms: this.now() - started }, auditBase);
    }
    try {
      const discovered = await this.provider.search(query, {
        ...settings,
        freshness: input.freshness
      });
      const allowed = [];
      for (const row of discovered) {
        if (allowed.length >= settings.max_results) break;
        const policy = await evaluateUrl(row.url, {
          mode: settings.policy_mode,
          rules: settings.url_rules,
          resolveHost: this.provider.resolveHost
        });
        if (!policy.allowed) continue;
        const normalized = { ...row, url: policy.url };
        if (input.requested_depth === "full_page" && settings.allow_full_page_fetch) {
          try {
            const page = await this.provider.fetchPage(policy.url, settings);
            normalized.url = page.url;
            normalized.page_excerpt = page.text;
          } catch (error) {
            if (error.code === "URL_BLOCKED") continue;
          }
        }
        allowed.push(normalized);
      }
      const formatted = formatResults(allowed, { reason, origin, settings });
      const value = {
        query,
        reason: formatted.reason,
        status: allowed.length ? "ok" : "no_results",
        blocked_reason: null,
        result_count: formatted.results.length,
        results: formatted.results,
        condensed_text: formatted.condensed_text,
        output_budget_chars: formatted.output_budget_chars,
        truncated: formatted.truncated,
        timing_ms: this.now() - started,
        cache_hit: false,
        policy_mode: settings.policy_mode
      };
      if (settings.cache_ttl_seconds > 0 && allowed.length) {
        this.cache.set(cacheKey, {
          expiresAt: this.now() + settings.cache_ttl_seconds * 1000,
          value
        });
      }
      return this.finish(value, auditBase);
    } catch (error) {
      return this.finish({
        query,
        reason,
        status: error.code === "URL_BLOCKED" ? "blocked" : "unavailable",
        blocked_reason: error.blockedReason || null,
        error: cleanError(error),
        result_count: 0,
        results: [],
        condensed_text: "",
        timing_ms: this.now() - started,
        cache_hit: false,
        policy_mode: settings.policy_mode
      }, auditBase);
    }
  }

  consumeRateLimit(key, maximum) {
    const cutoff = this.now() - 60000;
    const recent = (this.rateLimits.get(key) || []).filter((timestamp) => timestamp > cutoff);
    if (recent.length >= maximum) {
      this.rateLimits.set(key, recent);
      return false;
    }
    recent.push(this.now());
    this.rateLimits.set(key, recent);
    return true;
  }

  finish(result, base) {
    result.user_message ||= userMessage(result);
    this.audit({
      ...base,
      status: result.status,
      allowed: result.status === "ok" || result.status === "no_results",
      blocked_reason: result.blocked_reason || null,
      result_count: result.result_count,
      timing_ms: result.timing_ms,
      cache_hit: result.cache_hit
    });
    return result;
  }

  audit(entry) {
    fs.mkdirSync(this.dataDir, { recursive: true });
    fs.appendFileSync(path.join(this.dataDir, "audit.jsonl"), `${JSON.stringify({
      timestamp: new Date().toISOString(),
      ...entry
    })}\n`);
  }
}

function trustedOrigin(ctx, fallback) {
  return normalizeOrigin(ctx?.origin || ctx?.platform || fallback || "other");
}

function blockedResult(query, reason, blockedReason, settings, started, now = Date.now()) {
  return {
    query,
    reason,
    status: "blocked",
    blocked_reason: blockedReason,
    result_count: 0,
    results: [],
    condensed_text: "",
    timing_ms: Math.max(0, now - started),
    cache_hit: false,
    policy_mode: settings.policy_mode
  };
}

function cleanError(error) {
  if (error?.name === "AbortError") return "Search provider timed out.";
  return "Search provider is unavailable.";
}

function userMessage(result) {
  if (result.status === "ok") return result.condensed_text || "Web search completed without a usable summary.";
  if (result.status === "no_results") return "No permitted web results were found.";
  if (result.status === "unavailable") return "Web search is currently unavailable.";
  if (result.blocked_reason === "rate_limited") return "Web search is temporarily rate-limited.";
  if (result.blocked_reason === "origin_not_allowed") return "Web search is not enabled for this platform.";
  if (result.blocked_reason === "tool_disabled") return "Web search is disabled.";
  return "Web search was blocked by the configured safety policy.";
}

module.exports = {
  WebSearchTool,
  blockedResult,
  cleanError,
  trustedOrigin,
  userMessage
};