// ============================================================================
// @mintel/page-audit — DataForSEO API Client
// Uses native fetch (no axios) to avoid Node event loop exit during polling.
// Docs: https://docs.dataforseo.com/v3/on_page/
// ============================================================================

import type { PageAuditData, AuditIssue } from "./types.js";

const API_BASE = "https://api.dataforseo.com/v3";

/** Authenticated DataForSEO client */
export class DataForSeoClient {
    private auth: string;

    constructor(login: string, password: string) {
        this.auth = Buffer.from(`${login}:${password}`).toString("base64");
    }

    private get headers(): Record<string, string> {
        return {
            Authorization: `Basic ${this.auth}`,
            "Content-Type": "application/json",
        };
    }

    private async apiGet(path: string): Promise<any> {
        const resp = await fetch(`${API_BASE}${path}`, { headers: this.headers });
        if (!resp.ok) throw new Error(`DataForSEO GET ${path} failed: ${resp.status}`);
        return resp.json();
    }

    private async apiPost(path: string, body: any): Promise<any> {
        const resp = await fetch(`${API_BASE}${path}`, {
            method: "POST",
            headers: this.headers,
            body: JSON.stringify(body),
        });
        if (!resp.ok) throw new Error(`DataForSEO POST ${path} failed: ${resp.status}`);
        return resp.json();
    }

    /**
     * Start an On-Page crawl for a domain and return the task ID.
     */
    async startCrawl(domain: string, maxCrawlPages = 50): Promise<string> {
        const url = domain.startsWith("http") ? domain : `https://${domain}`;

        const data = await this.apiPost("/on_page/task_post", [
            {
                target: url,
                max_crawl_pages: maxCrawlPages,
                load_resources: true,
                enable_javascript: true,
                enable_browser_rendering: true,
                check_spell: false,
                calculate_keyword_density: false,
            },
        ]);

        const task = data?.tasks?.[0];
        if (!task?.id) {
            throw new Error(`DataForSEO task creation failed: ${JSON.stringify(task?.status_message || "unknown")}`);
        }

        return task.id;
    }

    /**
     * Check if a task is ready via the tasks_ready endpoint.
     */
    async isTaskReady(taskId: string): Promise<boolean> {
        const data = await this.apiGet("/on_page/tasks_ready");
        const readyTasks: string[] = data?.tasks?.[0]?.result?.map((t: any) => t.id) || [];
        return readyTasks.includes(taskId);
    }

    /**
     * Poll for task completion using tasks_ready endpoint.
     * DataForSEO crawls can take 2-5 minutes.
     */
    async waitForTask(taskId: string, timeoutMs = 300_000): Promise<void> {
        const start = Date.now();
        let delay = 15_000;
        let pollCount = 0;

        // Force Node event loop active
        const keepAlive = setInterval(() => { }, 1000);

        try {
            while (Date.now() - start < timeoutMs) {
                await this.sleep(delay);
                pollCount++;

                const ready = await this.isTaskReady(taskId);
                const elapsed = Math.round((Date.now() - start) / 1000);
                console.log(`  📊 Poll #${pollCount}: ${ready ? "READY ✅" : "not ready"} (${elapsed}s elapsed)`);

                if (ready) {
                    // Short grace period so the pages endpoint settles
                    await this.sleep(5_000);
                    return;
                }

                delay = Math.min(delay * 1.3, 30_000);
            }

            throw new Error(`DataForSEO task ${taskId} timed out after ${timeoutMs / 1000}s`);
        } finally {
            clearInterval(keepAlive);
        }
    }

    /**
     * Sleep that keeps the Node event loop alive.
     */
    private sleep(ms: number): Promise<void> {
        return new Promise((resolve) => {
            const timer = setTimeout(resolve, ms);
            // Explicitly ref the timer to prevent Node from exiting
            if (timer && typeof timer === "object" && "ref" in timer) {
                (timer as NodeJS.Timeout).ref();
            }
        });
    }

    /**
     * Fetch the crawl summary.
     */
    async getCrawlSummary(taskId: string): Promise<any> {
        const data = await this.apiGet(`/on_page/summary/${taskId}`);
        return data?.tasks?.[0]?.result?.[0] || null;
    }

    /**
     * Fetch all page-level results.
     */
    async getPages(taskId: string, limit = 100, offset = 0): Promise<any[]> {
        const data = await this.apiPost("/on_page/pages", [
            { id: taskId, limit, offset },
        ]);
        return data?.tasks?.[0]?.result?.[0]?.items || [];
    }

    /**
     * Fetch non-indexable pages.
     */
    async getNonIndexable(taskId: string): Promise<any[]> {
        const data = await this.apiPost("/on_page/non_indexable", [
            { id: taskId, limit: 100, offset: 0 },
        ]);
        return data?.tasks?.[0]?.result?.[0]?.items || [];
    }

    /**
     * Fetch broken resources (404s, timeouts, etc.)
     */
    async getBrokenResources(taskId: string): Promise<any[]> {
        const data = await this.apiPost("/on_page/resources", [
            { id: taskId, limit: 100, filters: [["status_code", ">", "399"]] },
        ]);
        return data?.tasks?.[0]?.result?.[0]?.items || [];
    }
}

/**
 * Normalize a DataForSEO raw page result into our PageAuditData type.
 */
export function normalizePage(raw: any): PageAuditData {
    const issues: AuditIssue[] = [];

    const checks = raw.checks || {};

    if (checks.no_title) issues.push({ code: "NO_TITLE", severity: "critical", message: "Seite hat keinen <title> Tag" });
    if (checks.title_too_long) issues.push({ code: "TITLE_TOO_LONG", severity: "warning", message: `Title zu lang (${raw.meta?.title?.length || "?"} Zeichen, max 60)` });
    if (checks.no_description) issues.push({ code: "NO_META_DESCRIPTION", severity: "warning", message: "Keine Meta-Description" });
    if (checks.description_too_long) issues.push({ code: "META_DESC_TOO_LONG", severity: "info", message: "Meta-Description zu lang (max 160)" });
    if (checks.no_h1_tag) issues.push({ code: "NO_H1", severity: "critical", message: "Kein H1-Tag auf der Seite" });
    if (checks.duplicate_h1_tag) issues.push({ code: "DUPLICATE_H1", severity: "warning", message: "Mehrere H1-Tags gefunden" });
    if (checks.is_broken) issues.push({ code: "PAGE_BROKEN", severity: "critical", message: `HTTP ${raw.status_code}: Seite nicht erreichbar` });
    if (checks.low_content_rate) issues.push({ code: "THIN_CONTENT", severity: "warning", message: "Zu wenig Content (dünne Seite)" });
    if (checks.has_render_blocking_resources) issues.push({ code: "RENDER_BLOCKING", severity: "warning", message: "Render-blockierende Ressourcen gefunden" });
    if (checks.image_not_optimized) issues.push({ code: "UNOPTIMIZED_IMAGES", severity: "info", message: "Nicht-optimierte Bilder vorhanden" });

    const imagesWithoutAlt = raw.checks?.no_image_alt ? (raw.meta?.images_count || 0) : 0;

    return {
        url: raw.url,
        statusCode: raw.status_code,
        pageTitle: raw.meta?.title || null,
        metaDescription: raw.meta?.description || null,
        h1: raw.meta?.htags?.h1?.[0] || null,
        wordCount: raw.meta?.content?.words_count || 0,
        loadTime: raw.page_timing?.time_to_interactive || null,
        links: {
            internal: raw.meta?.internal_links_count || 0,
            external: raw.meta?.external_links_count || 0,
            broken: 0,
        },
        images: {
            total: raw.meta?.images_count || 0,
            missingAlt: imagesWithoutAlt,
        },
        seo: {
            hasViewport: !raw.checks?.no_viewport_tag,
            hasCanonical: !!raw.meta?.canonical,
            isIndexable: !raw.checks?.is_4xx_code && !raw.checks?.is_5xx_code,
            robotsTxt: raw.meta?.robots || null,
            ogTitle: raw.meta?.social_media_tags?.og_title || null,
            ogDescription: raw.meta?.social_media_tags?.og_description || null,
        },
        performance: {
            cls: raw.page_timing?.cumulative_layout_shift || null,
            lcp: raw.page_timing?.largest_contentful_paint || null,
            fid: raw.page_timing?.first_input_delay || null,
            ttfb: raw.page_timing?.waiting_time || null,
        },
        issues,
    };
}