frontend/src/hooks/useSession.js

import { useState, useCallback } from 'react'

export function useSession() {
  const [sessionId, setSessionId] = useState(null)
  const [stems, setStems] = useState([])
  const [detection, setDetection] = useState(null)
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState(null)

  const clearError = useCallback(() => {
    setError(null)
  }, [])

  // Upload files and automatically run detection
  const upload = useCallback(async (formData) => {
    setLoading(true)
    setError(null)

    try {
      // Step 1: Upload files (formData already prepared by FileUpload component)
      const uploadResponse = await fetch('/api/upload', {
        method: 'POST',
        body: formData
      })

      if (!uploadResponse.ok) {
        const data = await uploadResponse.json().catch(() => ({}))
        throw new Error(data.detail || `Upload failed: ${uploadResponse.status}`)
      }

      const uploadData = await uploadResponse.json()
      console.log('Upload response:', uploadData)

      setSessionId(uploadData.session_id)
      setStems(uploadData.stems)

      // Step 2: Automatically run detection with the session_id we just got
      const detectResponse = await fetch(`/api/detect/${uploadData.session_id}`, {
        method: 'POST'
      })

      if (!detectResponse.ok) {
        const data = await detectResponse.json().catch(() => ({}))
        throw new Error(data.detail || `Detection failed: ${detectResponse.status}`)
      }

      const detectData = await detectResponse.json()
      console.log('Detection response:', detectData)
      setDetection(detectData)

      return { upload: uploadData, detection: detectData }
    } catch (err) {
      console.error('Error:', err)
      setError(err.message)
      return null
    } finally {
      setLoading(false)
    }
  }, [])

  // Manual detect (if needed separately)
  const detect = useCallback(async (sid = null) => {
    const id = sid || sessionId
    if (!id) {
      setError('No session to detect')
      return null
    }

    setLoading(true)
    setError(null)

    try {
      const response = await fetch(`/api/detect/${id}`, {
        method: 'POST'
      })

      if (!response.ok) {
        const data = await response.json().catch(() => ({}))
        throw new Error(data.detail || `Detection failed: ${response.status}`)
      }

      const data = await response.json()
      setDetection(data)
      return data
    } catch (err) {
      setError(err.message)
      return null
    } finally {
      setLoading(false)
    }
  }, [sessionId])

  const process = useCallback(async (semitones, targetBpm = null, regionStart = null, regionEnd = null) => {
    if (!sessionId) {
      setError('No session to process')
      return null
    }

    setLoading(true)
    setError(null)

    try {
      const body = { semitones, target_bpm: targetBpm }
      if (regionStart !== null && regionEnd !== null) {
        body.region_start = regionStart
        body.region_end = regionEnd
      }

      const response = await fetch(`/api/process/${sessionId}`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify(body)
      })

      if (!response.ok) {
        const data = await response.json().catch(() => ({}))
        throw new Error(data.detail || `Processing failed: ${response.status}`)
      }

      const data = await response.json()
      return data
    } catch (err) {
      setError(err.message)
      return null
    } finally {
      setLoading(false)
    }
  }, [sessionId])

  const getStems = useCallback(async () => {
    if (!sessionId) return null

    try {
      const response = await fetch(`/api/stems/${sessionId}`)

      if (!response.ok) {
        throw new Error('Failed to get stems')
      }

      const data = await response.json()
      return data
    } catch (err) {
      setError(err.message)
      return null
    }
  }, [sessionId])

  const loadPreset = useCallback(async (presetName) => {
    setLoading(true)
    setError(null)

    try {
      const uploadResponse = await fetch(`/api/preset/${presetName}`, { method: 'POST' })
      if (!uploadResponse.ok) {
        const data = await uploadResponse.json().catch(() => ({}))
        throw new Error(data.detail || `Failed to load preset: ${uploadResponse.status}`)
      }
      const uploadData = await uploadResponse.json()
      setSessionId(uploadData.session_id)
      setStems(uploadData.stems)

      const detectResponse = await fetch(`/api/detect/${uploadData.session_id}`, { method: 'POST' })
      if (!detectResponse.ok) {
        const data = await detectResponse.json().catch(() => ({}))
        throw new Error(data.detail || `Detection failed: ${detectResponse.status}`)
      }
      const detectData = await detectResponse.json()
      setDetection(detectData)

      return { upload: uploadData, detection: detectData }
    } catch (err) {
      setError(err.message)
      return null
    } finally {
      setLoading(false)
    }
  }, [])

  const generate = useCallback(async (regionStart, regionEnd, duration = 15.0, prompt = null) => {
    if (!sessionId) {
      setError('No session to generate')
      return null
    }

    setLoading(true)
    setError(null)

    try {
      const body = { region_start: regionStart, region_end: regionEnd, duration }
      if (prompt) {
        body.prompt = prompt
      }

      const response = await fetch(`/api/generate/${sessionId}`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify(body)
      })

      if (!response.ok) {
        const data = await response.json().catch(() => ({}))
        throw new Error(data.detail || `Generation failed: ${response.status}`)
      }

      const data = await response.json()
      return data
    } catch (err) {
      setError(err.message)
      return null
    } finally {
      setLoading(false)
    }
  }, [sessionId])

  return {
    sessionId,
    stems,
    detection,
    loading,
    error,
    upload,
    detect,
    process,
    generate,
    getStems,
    loadPreset,
    clearError
  }
}