'use client';

import { useState, useCallback } from 'react';
import {
  Input,
  Output,
  VideoSampleSink,
  VideoSampleSource,
  BlobSource,
  ALL_FORMATS,
  BufferTarget,
  Mp4OutputFormat,
  canEncodeVideo,
} from 'mediabunny';
import type { Rotation, VideoSample } from 'mediabunny';
import { getEasingFunction, type EasingFunction } from '@/lib/easing-functions';
import { createAvcEncodingConfig, AVC_LEVEL_4_0, AVC_LEVEL_5_1 } from '@/lib/video-encoding';

// Inlined constants (same pattern as Phase 41)
const DEFAULT_BITRATE = 8_000_000;
const TARGET_FRAME_RATE = 30;
const DEFAULT_INPUT_DURATION = 5;
const DEFAULT_OUTPUT_DURATION = 1.5;
const DEFAULT_EASING = 'easeInOutSine';
const MAX_OUTPUT_FPS = 60;

type VideoSampleLike = Parameters<VideoSampleSource['add']>[0];

export interface SpeedCurveProgress {
  status: 'idle' | 'processing' | 'complete' | 'error';
  message: string;
  progress: number; // 0-100
  error?: string;
}

interface UseApplySpeedCurveReturn {
  applySpeedCurve: (
    videoBlob: Blob,
    inputDuration?: number,
    outputDuration?: number,
    onProgress?: (progress: SpeedCurveProgress) => void,
    easingFunction?: EasingFunction | string,
    bitrate?: number
  ) => Promise<Blob | null>;
  progress: SpeedCurveProgress;
  reset: () => void;
}

// Helper to get video dimensions
const getVideoDimensions = (blob: Blob): Promise<{ width: number; height: number }> => {
  return new Promise((resolve, reject) => {
    const video = document.createElement('video');
    video.preload = 'metadata';
    video.onloadedmetadata = () => {
      resolve({ width: video.videoWidth, height: video.videoHeight });
      URL.revokeObjectURL(video.src);
    };
    video.onerror = () => {
      reject(new Error('Failed to load video metadata'));
      URL.revokeObjectURL(video.src);
    };
    video.src = URL.createObjectURL(blob);
  });
};

const normalizeRotation = (value: unknown): Rotation => {
  return value === 0 || value === 90 || value === 180 || value === 270 ? value : 0;
};

/**
 * Core speed curve processing logic shared by hook and standalone function.
 * Reads frames from a video blob and re-timestamps them using an easing function.
 */
async function applySpeedCurveCore(
  videoBlob: Blob,
  inputDuration: number,
  outputDuration: number,
  onProgress: ((progress: SpeedCurveProgress) => void) | undefined,
  easingFunction: EasingFunction | string,
  bitrate: number
): Promise<Blob> {
  let input: Input | null = null;
  let videoSource: VideoSampleSource | null = null;
  let output: Output | null = null;
  let outputStarted = false;

  try {
    // Helper to update progress
    const updateProgress = (
      status: SpeedCurveProgress['status'],
      message: string,
      progressValue: number
    ) => {
      const p: SpeedCurveProgress = { status, message, progress: progressValue };
      onProgress?.(p);
    };

    updateProgress('processing', 'Creating input from video blob...', 5);

    // Step 1: Create input from blob
    const blobSource = new BlobSource(videoBlob);
    input = new Input({
      source: blobSource,
      formats: ALL_FORMATS,
    });
    const videoTracks = await input.getVideoTracks();

    if (videoTracks.length === 0) {
      throw new Error('No video tracks found in input');
    }

    const videoTrack = videoTracks[0];
    const trackRotation = normalizeRotation(
      typeof videoTrack.rotation === 'number' ? videoTrack.rotation : undefined
    );

    // Step 2: Analyze metadata
    updateProgress('processing', 'Analyzing video metadata...', 10);

    const [trackDuration, containerDuration, packetStats, dimensions] = await Promise.all([
      videoTrack.computeDuration().catch(() => null),
      input.computeDuration().catch(() => null),
      videoTrack
        .computePacketStats()
        .catch((statsError: unknown) => {
          console.warn('Failed to compute packet stats', statsError);
          return null;
        }),
      getVideoDimensions(videoBlob).catch((e: unknown) => {
        console.warn('Failed to get video dimensions', e);
        return { width: 1920, height: 1080 }; // Fallback
      })
    ]);

    let resolvedBitrate = Number.isFinite(bitrate) ? bitrate : DEFAULT_BITRATE;
    if (packetStats?.averageBitrate && Number.isFinite(packetStats.averageBitrate)) {
      resolvedBitrate = Math.max(resolvedBitrate, packetStats.averageBitrate);
    }
    resolvedBitrate = Math.max(1, Math.floor(resolvedBitrate));

    const resolvedDuration =
      typeof trackDuration === 'number' && Number.isFinite(trackDuration) && trackDuration > 0
        ? trackDuration
        : typeof containerDuration === 'number' && Number.isFinite(containerDuration) && containerDuration > 0
          ? containerDuration
          : inputDuration;

    const frameRate =
      packetStats?.averagePacketRate && Number.isFinite(packetStats.averagePacketRate)
        ? packetStats.averagePacketRate
        : TARGET_FRAME_RATE;

    // The hook always uses the easing function passed by the caller (no adaptive easing)
    const easingToUse = easingFunction;

    const effectiveInputDuration =
      typeof resolvedDuration === 'number' && Number.isFinite(resolvedDuration) && resolvedDuration > 0
        ? resolvedDuration
        : inputDuration;

    const fpsDisplay = frameRate.toFixed(1);
    const bitrateDisplay = (resolvedBitrate / 1_000_000).toFixed(1);
    const durationDisplay = effectiveInputDuration.toFixed(2);
    const metadataSummary = `${durationDisplay}s @ ${fpsDisplay}fps @ ${bitrateDisplay}Mbps`;

    updateProgress('processing', `Metadata analyzed (${metadataSummary})`, 18);

    // Step 3: Create output with video source
    updateProgress('processing', 'Configuring encoder...', 20);

    const sourceWidth = dimensions.width;
    const sourceHeight = dimensions.height;
    const targetFramerate = MAX_OUTPUT_FPS;

    type VideoTier = {
      width: number;
      height: number;
      bitrate: number;
      codec: string;
      label: string;
    };

    // Full quality mode: preserve source bitrate at each tier
    const tiers: VideoTier[] = [
      // Tier 1: Original Resolution with High profile 5.1
      {
        width: sourceWidth,
        height: sourceHeight,
        bitrate: resolvedBitrate,
        codec: AVC_LEVEL_5_1,
        label: 'Original',
      },
      // Tier 2: 1080p with High profile 4.0 - preserve source bitrate
      {
        width: Math.min(sourceWidth, 1920),
        height: Math.min(sourceHeight, 1080),
        bitrate: resolvedBitrate,
        codec: AVC_LEVEL_4_0,
        label: '1080p',
      },
      // Tier 3: 720p with High profile 4.0 - preserve source bitrate
      {
        width: Math.min(sourceWidth, 1280),
        height: Math.min(sourceHeight, 720),
        bitrate: resolvedBitrate,
        codec: AVC_LEVEL_4_0,
        label: '720p',
      },
    ];

    let selectedConfig:
      | (VideoTier & { width: number; height: number; framerate: number })
      | null = null;

    for (const tier of tiers) {
      // Maintain aspect ratio if downscaling
      let targetWidth = tier.width;
      let targetHeight = tier.height;

      if (targetWidth < sourceWidth || targetHeight < sourceHeight) {
        const scale = Math.min(tier.width / sourceWidth, tier.height / sourceHeight);
        targetWidth = Math.round(sourceWidth * scale) & ~1; // Ensure even dimensions
        targetHeight = Math.round(sourceHeight * scale) & ~1;
      }

      const supported = await canEncodeVideo('avc', {
        width: targetWidth,
        height: targetHeight,
        bitrate: tier.bitrate,
        fullCodecString: tier.codec,
      });

      if (supported) {
        selectedConfig = {
          ...tier,
          width: targetWidth,
          height: targetHeight,
          framerate: targetFramerate,
        };
        break;
      }
    }

    if (!selectedConfig) {
      throw new Error(
        'Device encoder does not support the required H.264 profiles for this video. Try reducing resolution/bitrate and retry.'
      );
    }

    updateProgress(
      'processing',
      `Encoder selected: ${selectedConfig.label} (${selectedConfig.width}x${selectedConfig.height} @ ${selectedConfig.framerate}fps)`,
      22
    );

    videoSource = new VideoSampleSource(
      createAvcEncodingConfig(
        selectedConfig.bitrate,
        selectedConfig.width,
        selectedConfig.height,
        selectedConfig.codec,
        selectedConfig.framerate
      )
    );

    const bufferTarget = new BufferTarget();
    output = new Output({
      format: new Mp4OutputFormat({ fastStart: 'in-memory' }),
      target: bufferTarget,
    });

    output.addVideoTrack(videoSource, { rotation: trackRotation, frameRate: selectedConfig.framerate });

    updateProgress('processing', 'Starting output encoding...', 25);

    await output.start();
    outputStarted = true;

    // Step 4: OUTPUT-DRIVEN FRAME EMISSION
    const minFrameInterval = 1 / selectedConfig.framerate;
    const totalOutputFrames = Math.floor(outputDuration * selectedConfig.framerate);

    // Resolve easing function once for efficiency
    const easingFunc = typeof easingToUse === 'string'
      ? getEasingFunction(easingToUse)
      : easingToUse;

    const emitSample = async (
      sourceSample: VideoSampleLike,
      timestamp: number,
      duration: number
    ) => {
      const outputSample = (sourceSample as VideoSample).clone();
      outputSample.setTimestamp(timestamp);
      outputSample.setDuration(duration);
      await videoSource!.add(outputSample);
      outputSample.close();
    };

    // OUTPUT-DRIVEN FRAME EMISSION using samplesAtTimestamps()
    updateProgress('processing', 'Preparing frame decoder...', 25);
    const sink = new VideoSampleSink(videoTrack);

    // Pre-calculate all source timestamps we need based on easing function
    const sourceTimestamps: number[] = [];
    const outputTimestamps: number[] = [];

    for (let outputSlot = 0; outputSlot < totalOutputFrames; outputSlot++) {
      const outputTime = outputSlot * minFrameInterval;
      const outputProgress = totalOutputFrames > 1
        ? outputSlot / (totalOutputFrames - 1)
        : 0;

      // Apply easing function: maps output progress to source progress
      const sourceProgress = easingFunc(outputProgress);

      // Map to source timestamp, clamped to valid range
      const sourceTime = Math.max(0, Math.min(
        sourceProgress * effectiveInputDuration,
        effectiveInputDuration - 0.001
      ));

      sourceTimestamps.push(sourceTime);
      outputTimestamps.push(outputTime);
    }

    // Use samplesAtTimestamps for efficient random-access decoding
    let emittedCount = 0;

    updateProgress('processing', `Processing ${totalOutputFrames} frames...`, 30);

    const samplesIterator = sink.samplesAtTimestamps(sourceTimestamps);

    for await (const sample of samplesIterator) {
      if (!sample) {
        console.warn(`[SpeedCurve] Null sample at index ${emittedCount}, skipping`);
        emittedCount++;
        continue;
      }

      const outputTime = outputTimestamps[emittedCount];

      await emitSample(sample, outputTime, minFrameInterval);
      sample.close();
      emittedCount++;

      // Update progress (30% to 90%)
      if (emittedCount % 10 === 0) {
        const emitProgress = emittedCount / totalOutputFrames;
        updateProgress(
          'processing',
          `Encoding: ${emittedCount}/${totalOutputFrames} frames...`,
          30 + emitProgress * 60
        );
      }
    }

    if (emittedCount === 0) {
      throw new Error('No frames were emitted from source video');
    }

    updateProgress('processing', 'Finalizing output...', 95);

    // Ensure encoder flushes SPS/PPS before finalizing
    await videoSource.close();
    videoSource = null; // Already closed, prevent double-close in finally
    // Step 5: Finalize and get output blob
    await output.finalize();
    outputStarted = false; // Successfully finalized, no need to cancel in finally
    output = null;
    const buffer = bufferTarget.buffer;

    if (!buffer) {
      throw new Error('Failed to generate output buffer');
    }

    const outputBlob = new Blob([buffer], { type: 'video/mp4' });

    updateProgress(
      'complete',
      `Successfully created ${(outputBlob.size / 1024 / 1024).toFixed(2)}MB video`,
      100
    );

    return outputBlob;
  } finally {
    if (videoSource) {
      try {
        await videoSource.close();
      } catch (e) {
        console.warn('Failed to close videoSource:', e);
      }
    }
    if (output && outputStarted) {
      try {
        await output.cancel();
      } catch (e) {
        console.warn('Failed to cancel output:', e);
      }
    }
    if (input) {
      try {
        input.dispose();
      } catch (e) {
        console.warn('Failed to dispose input:', e);
      }
    }
  }
}

/**
 * Standalone async function to apply a speed curve to a video blob.
 * Same implementation as the hook's applySpeedCurve, but without React state.
 */
export async function applySpeedCurveAsync(
  videoBlob: Blob,
  inputDuration: number = DEFAULT_INPUT_DURATION,
  outputDuration: number = DEFAULT_OUTPUT_DURATION,
  onProgress?: (progress: SpeedCurveProgress) => void,
  easingFunction: EasingFunction | string = DEFAULT_EASING,
  bitrate: number = DEFAULT_BITRATE
): Promise<Blob | null> {
  try {
    return await applySpeedCurveCore(
      videoBlob,
      inputDuration,
      outputDuration,
      onProgress,
      easingFunction,
      bitrate
    );
  } catch (error) {
    const errorMessage = error instanceof Error ? error.message : String(error);
    console.error('Speed curve error:', error);

    const errorProgress: SpeedCurveProgress = {
      status: 'error',
      message: `Error: ${errorMessage}`,
      progress: 0,
      error: errorMessage,
    };
    onProgress?.(errorProgress);

    return null;
  }
}

/**
 * Hook for applying speed curves to video using Mediabunny.
 * Uses easeInOutSine by default for smooth speed ramping.
 */
export const useApplySpeedCurve = (): UseApplySpeedCurveReturn => {
  const [progress, setProgress] = useState<SpeedCurveProgress>({
    status: 'idle',
    message: 'Ready',
    progress: 0,
  });

  const applySpeedCurve = useCallback(
    async (
      videoBlob: Blob,
      inputDuration: number = DEFAULT_INPUT_DURATION,
      outputDuration: number = DEFAULT_OUTPUT_DURATION,
      onProgress?: (progress: SpeedCurveProgress) => void,
      easingFunction: EasingFunction | string = DEFAULT_EASING,
      bitrate: number = DEFAULT_BITRATE
    ): Promise<Blob | null> => {
      try {
        // Reset progress
        const initialProgress: SpeedCurveProgress = {
          status: 'processing',
          message: 'Initializing...',
          progress: 0,
        };
        setProgress(initialProgress);
        onProgress?.(initialProgress);

        const result = await applySpeedCurveCore(
          videoBlob,
          inputDuration,
          outputDuration,
          (p) => {
            setProgress(p);
            onProgress?.(p);
          },
          easingFunction,
          bitrate
        );

        return result;
      } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        console.error('Speed curve error:', error);

        const errorProgress: SpeedCurveProgress = {
          status: 'error',
          message: `Error: ${errorMessage}`,
          progress: 0,
          error: errorMessage,
        };

        setProgress(errorProgress);
        onProgress?.(errorProgress);

        return null;
      }
    },
    []
  );

  const reset = useCallback(() => {
    setProgress({
      status: 'idle',
      message: 'Ready',
      progress: 0,
    });
  }, []);

  return {
    applySpeedCurve,
    progress,
    reset,
  };
};