import React, { useState, useRef, useEffect } from "react";
import { invoke } from "@tauri-apps/api/core";
import { listen } from "@tauri-apps/api/event";
import { ModelInfo } from "../../lib/types";
import ModelStatusButton from "./ModelStatusButton";
import ModelDropdown from "./ModelDropdown";
import DownloadProgressDisplay from "./DownloadProgressDisplay";

interface ModelStateEvent {
  event_type: string;
  model_id?: string;
  model_name?: string;
  error?: string;
}

interface DownloadProgress {
  model_id: string;
  downloaded: number;
  total: number;
  percentage: number;
}

type ModelStatus = "ready" | "loading" | "downloading" | "error" | "none";

interface DownloadStats {
  startTime: number;
  lastUpdate: number;
  totalDownloaded: number;
  speed: number;
}

interface ModelSelectorProps {
  onError?: (error: string) => void;
}

const ModelSelector: React.FC<ModelSelectorProps> = ({ onError }) => {
  const [models, setModels] = useState<ModelInfo[]>([]);
  const [currentModelId, setCurrentModelId] = useState<string>("");
  const [modelStatus, setModelStatus] = useState<ModelStatus>("loading");
  const [modelError, setModelError] = useState<string | null>(null);
  const [modelDownloadProgress, setModelDownloadProgress] = useState<
    Map<string, DownloadProgress>
  >(new Map());
  const [showModelDropdown, setShowModelDropdown] = useState(false);
  const [downloadStats, setDownloadStats] = useState<
    Map<string, DownloadStats>
  >(new Map());

  const dropdownRef = useRef<HTMLDivElement>(null);

  useEffect(() => {
    loadModels();
    loadCurrentModel();

    // Listen for model state changes
    const modelStateUnlisten = listen<ModelStateEvent>(
      "model-state-changed",
      (event) => {
        const { event_type, model_id, model_name, error } = event.payload;

        switch (event_type) {
          case "loading_started":
            setModelStatus("loading");
            setModelError(null);
            break;
          case "loading_completed":
            setModelStatus("ready");
            setModelError(null);
            if (model_id) setCurrentModelId(model_id);
            break;
          case "loading_failed":
            setModelStatus("error");
            setModelError(error || "Failed to load model");
            break;
        }
      },
    );

    // Listen for model download progress
    const downloadProgressUnlisten = listen<DownloadProgress>(
      "model-download-progress",
      (event) => {
        const progress = event.payload;
        setModelDownloadProgress((prev) => {
          const newMap = new Map(prev);
          newMap.set(progress.model_id, progress);
          return newMap;
        });
        setModelStatus("downloading");

        // Update download stats for speed calculation
        const now = Date.now();
        setDownloadStats((prev) => {
          const current = prev.get(progress.model_id);
          const newStats = new Map(prev);

          if (!current) {
            // First progress update - initialize
            newStats.set(progress.model_id, {
              startTime: now,
              lastUpdate: now,
              totalDownloaded: progress.downloaded,
              speed: 0,
            });
          } else {
            // Calculate speed over last few seconds
            const timeDiff = (now - current.lastUpdate) / 1000; // seconds
            const bytesDiff = progress.downloaded - current.totalDownloaded;

            if (timeDiff > 0.5) {
              // Update speed every 500ms
              const currentSpeed = bytesDiff / (1024 * 1024) / timeDiff; // MB/s
              // Smooth the speed with exponential moving average, but ensure positive values
              const validCurrentSpeed = Math.max(0, currentSpeed);
              const smoothedSpeed =
                current.speed > 0
                  ? current.speed * 0.8 + validCurrentSpeed * 0.2
                  : validCurrentSpeed;

              newStats.set(progress.model_id, {
                startTime: current.startTime,
                lastUpdate: now,
                totalDownloaded: progress.downloaded,
                speed: Math.max(0, smoothedSpeed),
              });
            }
          }

          return newStats;
        });
      },
    );

    // Listen for model download completion
    const downloadCompleteUnlisten = listen<string>(
      "model-download-complete",
      (event) => {
        const modelId = event.payload;
        setModelDownloadProgress((prev) => {
          const newMap = new Map(prev);
          newMap.delete(modelId);
          return newMap;
        });
        setDownloadStats((prev) => {
          const newStats = new Map(prev);
          newStats.delete(modelId);
          return newStats;
        });
        loadModels(); // Refresh models list

        // Auto-select the newly downloaded model
        setTimeout(() => {
          loadCurrentModel();
          handleModelSelect(modelId);
        }, 500);
      },
    );

    // Click outside to close dropdown
    const handleClickOutside = (event: MouseEvent) => {
      if (
        dropdownRef.current &&
        !dropdownRef.current.contains(event.target as Node)
      ) {
        setShowModelDropdown(false);
      }
    };

    document.addEventListener("mousedown", handleClickOutside);

    return () => {
      document.removeEventListener("mousedown", handleClickOutside);
      modelStateUnlisten.then((fn) => fn());
      downloadProgressUnlisten.then((fn) => fn());
      downloadCompleteUnlisten.then((fn) => fn());
    };
  }, []);

  const loadModels = async () => {
    try {
      const modelList = await invoke<ModelInfo[]>("get_available_models");
      setModels(modelList);
    } catch (err) {
      console.error("Failed to load models:", err);
    }
  };

  const loadCurrentModel = async () => {
    try {
      const current = await invoke<string>("get_current_model");
      setCurrentModelId(current);

      if (current) {
        // Check if model is actually loaded
        const transcriptionStatus = await invoke<string | null>(
          "get_transcription_model_status",
        );
        if (transcriptionStatus === current) {
          setModelStatus("ready");
        } else {
          setModelStatus("loading");
        }
      } else {
        setModelStatus("none");
      }
    } catch (err) {
      console.error("Failed to load current model:", err);
      setModelStatus("error");
      setModelError("Failed to check model status");
    }
  };

  const handleModelSelect = async (modelId: string) => {
    try {
      setModelError(null);
      setShowModelDropdown(false);
      await invoke("set_active_model", { modelId });
      setCurrentModelId(modelId);
    } catch (err) {
      const errorMsg = `${err}`;
      setModelError(errorMsg);
      setModelStatus("error");
      onError?.(errorMsg);
    }
  };

  const handleModelDownload = async (modelId: string) => {
    try {
      setModelError(null);
      await invoke("download_model", { modelId });
    } catch (err) {
      const errorMsg = `${err}`;
      setModelError(errorMsg);
      setModelStatus("error");
      onError?.(errorMsg);
    }
  };

  const getCurrentModel = () => {
    return models.find((m) => m.id === currentModelId);
  };

  const getModelDisplayText = (): string => {
    if (modelDownloadProgress.size > 0) {
      if (modelDownloadProgress.size === 1) {
        const [progress] = Array.from(modelDownloadProgress.values());
        const percentage = Math.max(
          0,
          Math.min(100, Math.round(progress.percentage)),
        );
        return `Downloading ${percentage}%`;
      } else {
        return `Downloading ${modelDownloadProgress.size} models...`;
      }
    }

    const currentModel = getCurrentModel();

    switch (modelStatus) {
      case "ready":
        return currentModel?.name || "Model Ready";
      case "loading":
        return currentModel ? `Loading ${currentModel.name}...` : "Loading...";
      case "error":
        return modelError || "Model Error";
      case "none":
        return "No Model - Download Required";
      default:
        return currentModel?.name || "Select Model";
    }
  };

  const handleModelDelete = async (modelId: string) => {
    await invoke("delete_model", { modelId });
    await loadModels();
    setModelError(null);
  };

  return (
    <>
      {/* Model Status and Switcher */}
      <div className="relative" ref={dropdownRef}>
        <ModelStatusButton
          status={modelStatus}
          displayText={getModelDisplayText()}
          isDropdownOpen={showModelDropdown}
          onClick={() => setShowModelDropdown(!showModelDropdown)}
        />

        {/* Model Dropdown */}
        {showModelDropdown && (
          <ModelDropdown
            models={models}
            currentModelId={currentModelId}
            downloadProgress={modelDownloadProgress}
            onModelSelect={handleModelSelect}
            onModelDownload={handleModelDownload}
            onModelDelete={handleModelDelete}
            onError={onError}
          />
        )}
      </div>

      {/* Download Progress Bar for Models */}
      <DownloadProgressDisplay
        downloadProgress={modelDownloadProgress}
        downloadStats={downloadStats}
      />
    </>
  );
};

export default ModelSelector;
