"use client";

import { useState, useEffect } from "react";
import Link from "next/link";
import { useTenant } from "@/contexts/TenantContext";

type Document = {
  id: number;
  text: string;
  created_at: string | null;
};

type DocumentListResponse = {
  documents: Document[];
  total: number;
  limit: number;
  offset: number;
};

const API_BASE =
  process.env.NEXT_PUBLIC_API_URL?.replace(/\/$/, "") || "http://localhost:8000";

export default function KnowledgeBasePage() {
  const { tenantId, isLoading: tenantLoading, role } = useTenant();
  const [documents, setDocuments] = useState<Document[]>([]);
  const [total, setTotal] = useState(0);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [searchFilter, setSearchFilter] = useState("");
  const [filterType, setFilterType] = useState<"all" | "pdf" | "text" | "faq" | "link">("all");
  const [isDeleting, setIsDeleting] = useState<number | null>(null);
  const [isDeletingAll, setIsDeletingAll] = useState(false);

  async function loadDocuments() {
    // Guard against empty tenant ID
    if (!tenantId || !tenantId.trim()) {
      setError("Please enter a tenant ID");
      setLoading(false);
      return;
    }

    setLoading(true);
    setError(null);

    try {
      const response = await fetch(`${API_BASE}/rag/list?limit=1000&offset=0`, {
        headers: {
          "x-tenant-id": tenantId,
          "x-user-role": role,
        },
      });

      if (!response.ok) {
        const errorData = await response.json().catch(() => ({}));
        const errorMsg = errorData.detail || errorData.message || `Failed to load documents (${response.status})`;
        
        if (response.status === 400) {
          throw new Error(errorMsg.includes("tenant") 
            ? "Missing tenant ID. Please enter a tenant ID in the navbar."
            : errorMsg);
        } else if (response.status === 503) {
          throw new Error("Cannot connect to RAG MCP server. Please ensure the RAG server is running.");
        } else {
          throw new Error(errorMsg);
        }
      }

      const data: DocumentListResponse = await response.json();
      setDocuments(data.documents || []);
      setTotal(data.total || 0);
    } catch (err) {
      console.error(err);
      setError(
        err instanceof Error
          ? err.message
          : "Failed to load knowledge base. Please check if the backend services are running.",
      );
    } finally {
      setLoading(false);
    }
  }

  useEffect(() => {
    // Wait for tenant context to finish loading, then load documents if tenant ID is available
    if (!tenantLoading && tenantId && tenantId.trim()) {
      loadDocuments();
    }
  }, [tenantId, tenantLoading]);

  // Filter documents based on search and type
  const filteredDocuments = documents.filter((doc) => {
    const matchesSearch =
      !searchFilter ||
      doc.text.toLowerCase().includes(searchFilter.toLowerCase());
    
    // Simple heuristics for document type detection
    const textLower = doc.text.toLowerCase();
    let docType: "pdf" | "text" | "faq" | "link" = "text";
    
    if (textLower.includes("http://") || textLower.includes("https://") || textLower.includes("www.")) {
      docType = "link";
    } else if (
      textLower.includes("q:") ||
      textLower.includes("question:") ||
      textLower.includes("faq") ||
      textLower.includes("frequently asked")
    ) {
      docType = "faq";
    } else if (textLower.includes(".pdf") || textLower.includes("pdf document")) {
      docType = "pdf";
    }

    const matchesType = filterType === "all" || docType === filterType;
    return matchesSearch && matchesType;
  });

  const getDocumentType = (text: string): "pdf" | "text" | "faq" | "link" => {
    const textLower = text.toLowerCase();
    if (textLower.includes("http://") || textLower.includes("https://") || textLower.includes("www.")) {
      return "link";
    } else if (
      textLower.includes("q:") ||
      textLower.includes("question:") ||
      textLower.includes("faq") ||
      textLower.includes("frequently asked")
    ) {
      return "faq";
    } else if (textLower.includes(".pdf") || textLower.includes("pdf document")) {
      return "pdf";
    }
    return "text";
  };

  const getTypeColor = (type: string) => {
    switch (type) {
      case "pdf":
        return "bg-red-500/20 text-red-300 border-red-500/30";
      case "faq":
        return "bg-purple-500/20 text-purple-300 border-purple-500/30";
      case "link":
        return "bg-blue-500/20 text-blue-300 border-blue-500/30";
      default:
        return "bg-slate-500/20 text-slate-300 border-slate-500/30";
    }
  };

  async function handleDeleteDocument(documentId: number) {
    if (!tenantId.trim() || isDeleting !== null) return;
    setIsDeleting(documentId);

    try {
      const response = await fetch(`${API_BASE}/rag/delete/${documentId}`, {
        method: "DELETE",
        headers: {
          "x-tenant-id": tenantId,
          "x-user-role": role,
        },
      });

      if (!response.ok) {
        const errorData = await response.json().catch(() => ({}));
        const errorMsg = errorData.detail || `Failed to delete document: ${response.status}`;
        throw new Error(errorMsg);
      }

      // Remove from local state and update total
      setDocuments(docs => docs.filter(doc => doc.id !== documentId));
      setTotal(prev => Math.max(0, prev - 1));
    } catch (err) {
      console.error(err);
      setError(
        err instanceof Error
          ? err.message
          : "Failed to delete document",
      );
    } finally {
      setIsDeleting(null);
    }
  }

  async function handleDeleteAll() {
    if (!tenantId.trim() || isDeletingAll) return;
    
    if (!confirm("Are you sure you want to delete ALL documents for this tenant? This action cannot be undone.")) {
      return;
    }

    setIsDeletingAll(true);

    try {
      const response = await fetch(`${API_BASE}/rag/delete-all`, {
        method: "DELETE",
        headers: {
          "x-tenant-id": tenantId,
          "x-user-role": role,
        },
      });

      if (!response.ok) {
        throw new Error(`Failed to delete all documents: ${response.status}`);
      }

      const data = await response.json();
      setDocuments([]);
      setTotal(0);
    } catch (err) {
      console.error(err);
      setError(
        err instanceof Error
          ? err.message
          : "Failed to delete all documents",
      );
    } finally {
      setIsDeletingAll(false);
    }
  }

  return (
    <main className="mx-auto flex min-h-screen max-w-7xl flex-col gap-8 px-4 pb-16 pt-12 sm:px-6 lg:px-8">
      {/* Header */}
      <header className="flex flex-wrap items-center justify-between gap-4 rounded-2xl border border-white/10 bg-white/5 px-6 py-4 text-sm text-slate-100 shadow-lg shadow-slate-950/40">
        <div className="flex items-center gap-3">
          <Link
            href="/"
            className="inline-flex h-10 w-10 items-center justify-center rounded-2xl bg-gradient-to-br from-sky-400 to-cyan-500 text-slate-950 transition hover:scale-105"
          >
            ←
          </Link>
          <div>
            <h1 className="text-xl font-semibold">Knowledge Base Library</h1>
            <p className="text-xs text-slate-400">
              All ingested documents, PDFs, FAQs, links, and text content
            </p>
          </div>
        </div>
        <div className="flex items-center gap-3">
          {documents.length > 0 && (
            <button
              onClick={handleDeleteAll}
              disabled={isDeletingAll}
              className="rounded-full border border-red-500/50 bg-red-500/10 px-5 py-2 text-sm font-semibold text-red-300 transition hover:bg-red-500/20 disabled:opacity-60"
            >
              {isDeletingAll ? "Deleting…" : "Delete All"}
            </button>
          )}
          <button
            onClick={loadDocuments}
            disabled={loading}
            className="rounded-full bg-gradient-to-r from-sky-400 to-cyan-500 px-5 py-2 text-sm font-semibold text-slate-950 shadow-lg shadow-cyan-500/30 transition hover:-translate-y-0.5 disabled:opacity-60"
          >
            {loading ? "Loading…" : "Refresh"}
          </button>
        </div>
      </header>

      {/* Stats & Filters */}
      <div className="flex flex-wrap items-center justify-between gap-4 rounded-2xl border border-white/10 bg-slate-950/40 p-6">
        <div className="flex flex-wrap items-center gap-6">
          <div>
            <p className="text-xs uppercase tracking-widest text-slate-400">
              Total Documents
            </p>
            <p className="mt-1 text-2xl font-semibold text-white">{total}</p>
          </div>
          <div>
            <p className="text-xs uppercase tracking-widest text-slate-400">
              Filtered
            </p>
            <p className="mt-1 text-2xl font-semibold text-cyan-300">
              {filteredDocuments.length}
            </p>
          </div>
        </div>

        <div className="flex flex-wrap items-center gap-3">
          <input
            type="text"
            placeholder="Search documents..."
            value={searchFilter}
            onChange={(e) => setSearchFilter(e.target.value)}
            className="rounded-full border border-white/10 bg-white/5 px-4 py-2 text-sm text-white outline-none focus:border-cyan-300"
          />
          <div className="flex gap-2">
            {(["all", "text", "pdf", "faq", "link"] as const).map((type) => (
              <button
                key={type}
                onClick={() => setFilterType(type)}
                className={`rounded-full px-4 py-2 text-xs font-semibold uppercase tracking-wider transition ${
                  filterType === type
                    ? "bg-cyan-500 text-slate-950"
                    : "bg-white/5 text-slate-300 hover:bg-white/10"
                }`}
              >
                {type}
              </button>
            ))}
          </div>
        </div>
      </div>

      {/* Error Message */}
      {error && (
        <div className="rounded-2xl border border-red-500/40 bg-red-500/10 px-6 py-4 text-red-200">
          <p className="font-semibold">⚠️ Error loading knowledge base</p>
          <p className="mt-1 text-sm">{error}</p>
          <button
            onClick={() => {
              setError(null);
              loadDocuments();
            }}
            className="mt-3 rounded-lg border border-red-500/50 bg-red-500/20 px-4 py-2 text-sm font-semibold text-red-200 transition hover:bg-red-500/30"
          >
            Try Again
          </button>
        </div>
      )}

      {/* Documents Grid */}
      {loading ? (
        <div className="flex items-center justify-center py-20">
          <p className="text-slate-400">Loading documents...</p>
        </div>
      ) : filteredDocuments.length === 0 ? (
        <div className="flex flex-col items-center justify-center rounded-2xl border border-white/10 bg-slate-950/40 py-20">
          <p className="text-lg font-semibold text-slate-300">
            No documents found
          </p>
          <p className="mt-2 text-sm text-slate-400">
            {documents.length === 0
              ? "Start by ingesting some content in the Knowledge Base panel."
              : "Try adjusting your search or filter criteria."}
          </p>
        </div>
      ) : (
        <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-3">
          {filteredDocuments.map((doc) => {
            const docType = getDocumentType(doc.text);
            const preview = doc.text.slice(0, 200) + (doc.text.length > 200 ? "..." : "");
            
            return (
              <div
                key={doc.id}
                className="group relative rounded-2xl border border-white/10 bg-slate-950/40 p-5 transition hover:border-cyan-500/50 hover:bg-slate-900/60"
              >
                <div className="mb-3 flex items-start justify-between gap-2">
                  <span
                    className={`rounded-full border px-2.5 py-1 text-xs font-semibold uppercase tracking-wider ${getTypeColor(
                      docType,
                    )}`}
                  >
                    {docType}
                  </span>
                  {doc.created_at && (
                    <span className="text-xs text-slate-500">
                      {new Date(doc.created_at).toLocaleDateString()}
                    </span>
                  )}
                </div>
                <p className="text-sm leading-relaxed text-slate-200 line-clamp-6">
                  {preview}
                </p>
                <div className="mt-4 flex items-center justify-between">
                  <div className="flex items-center gap-2 text-xs text-slate-400">
                    <span>ID: {doc.id}</span>
                    <span>•</span>
                    <span>{doc.text.length} chars</span>
                  </div>
                  <button
                    onClick={() => handleDeleteDocument(doc.id)}
                    disabled={isDeleting === doc.id}
                    className="rounded-lg border border-red-500/50 bg-red-500/10 px-3 py-1 text-xs font-semibold text-red-300 transition hover:bg-red-500/20 disabled:opacity-60"
                  >
                    {isDeleting === doc.id ? "Deleting…" : "Delete"}
                  </button>
                </div>
              </div>
            );
          })}
        </div>
      )}

      {/* Footer */}
      <div className="mt-8 rounded-2xl border border-white/10 bg-white/5 px-6 py-4 text-center text-sm text-slate-400">
        <p>
          Knowledge base powered by pgvector + MiniLM embeddings •{" "}
          <Link href="/" className="text-cyan-300 hover:text-cyan-200">
            Back to Console
          </Link>
        </p>
      </div>
    </main>
  );
}