import React, { useState, useMemo } from 'react'
import { View, Text, TextInput, TouchableOpacity, StyleSheet, KeyboardAvoidingView, ScrollView } from 'react-native'
import { useSafeAreaInsets } from 'react-native-safe-area-context'
import DateTimePicker, { DateTimePickerEvent } from '@react-native-community/datetimepicker'
import { Measurement } from '../types'
import { generateId } from '../utils/uuid'

type Props = {
  onSubmit: (m: Measurement) => void
  initialValues?: Partial<Measurement>
  isEdit?: boolean
}

type FieldDef = {
  key: keyof Measurement
  label: string
  placeholder: string
  keyboardType: 'decimal-pad' | 'number-pad'
  computed?: boolean
}

const fields: FieldDef[] = [
  { key: 'weight', label: 'Gewicht (kg)', placeholder: '75.5', keyboardType: 'decimal-pad' },
  { key: 'bmi', label: 'BMI', placeholder: '22.3', keyboardType: 'decimal-pad' },
  { key: 'bodyFatPercentage', label: 'Vetpercentage (%)', placeholder: '15.2', keyboardType: 'decimal-pad' },
  { key: 'fatMass', label: 'Vetmassa (kg)', placeholder: '11.5', keyboardType: 'decimal-pad', computed: true },
  { key: 'musclePercentage', label: 'Spierpercentage (%)', placeholder: '40.1', keyboardType: 'decimal-pad' },
  { key: 'muscleMass', label: 'Spiermassa (kg)', placeholder: '30.3', keyboardType: 'decimal-pad', computed: true },
  { key: 'visceralFat', label: 'Buikvet (index)', placeholder: '8', keyboardType: 'number-pad' },
  { key: 'bmr', label: 'Stofwisseling (kcal)', placeholder: '1650', keyboardType: 'number-pad' },
]

export default function MeasurementForm({ onSubmit, initialValues, isEdit }: Props) {
  const insets = useSafeAreaInsets()
  const [pickerOpen, setPickerOpen] = useState(false)
  const [measurementDate, setMeasurementDate] = useState<Date>(new Date())
  const [values, setValues] = useState<Record<string, string>>(() => {
    const init: Record<string, string> = {}
    for (const f of fields) {
      if (f.computed) continue
      init[f.key] = initialValues?.[f.key]?.toString() ?? ''
    }
    return init
  })



function toFloat(s: string): number {
  return parseFloat(s.replace(',', '.')) || 0
}

function toInt(s: string): number {
  return parseInt(s.replace(',', '.'), 10) || 0
}


  const weight = toFloat(values.weight)
  const bodyFatPct = toFloat(values.bodyFatPercentage)
  const musclePct = toFloat(values.musclePercentage)

  const computed = useMemo(() => ({
    fatMass: weight > 0 && bodyFatPct > 0 ? ((weight * bodyFatPct) / 100).toFixed(1) : '',
    muscleMass: weight > 0 && musclePct > 0 ? ((weight * musclePct) / 100).toFixed(1) : '',
  }), [weight, bodyFatPct, musclePct])

  const handleSubmit = () => {
    const now = new Date().toISOString()
    const m: Measurement = {
      id: isEdit && initialValues?.id ? initialValues.id : generateId(),
      weight,
      bmi: toFloat(values.bmi),
      bodyFatPercentage: bodyFatPct,
      fatMass: toFloat(computed.fatMass),
      musclePercentage: musclePct,
      muscleMass: toFloat(computed.muscleMass),
      visceralFat: toInt(values.visceralFat),
      bmr: toFloat(values.bmr),
      measuredAt: measurementDate.toISOString(),
      createdAt: isEdit && initialValues?.createdAt ? initialValues.createdAt : now,
      updatedAt: now,
    }
    onSubmit(m)
  }

  const setField = (key: string, value: string) => {
    setValues(prev => ({ ...prev, [key]: value }))
  }

  const onDateChange = (_event: DateTimePickerEvent, selectedDate?: Date) => {
    setPickerOpen(false)
    if (selectedDate) {
      setMeasurementDate(selectedDate)
    }
  }

  return (
    <KeyboardAvoidingView behavior="padding" style={styles.container}>
      <ScrollView contentContainerStyle={styles.scroll} keyboardShouldPersistTaps="handled">
        <View style={styles.field}>
          <Text style={styles.label}>Datum</Text>
          <TouchableOpacity style={styles.dateButton} onPress={() => setPickerOpen(true)}>
            <Text style={styles.dateButtonText}>
              {measurementDate.toLocaleDateString('nl-NL', {
                weekday: 'long',
                day: 'numeric',
                month: 'long',
                year: 'numeric',
              })}
            </Text>
          </TouchableOpacity>
        </View>

        {pickerOpen && (
          <DateTimePicker
            value={measurementDate}
            mode="date"
            display="default"
            onChange={onDateChange}
          />
        )}

        {fields.map(f => {
          if (f.computed) {
            const calcValue = f.key === 'fatMass' ? computed.fatMass : computed.muscleMass
            return (
              <View key={f.key} style={styles.field}>
                <Text style={styles.label}>{f.label}</Text>
                <View style={[styles.input, styles.computedInput]}>
                  <Text style={styles.computedText}>{calcValue || '—'}</Text>
                </View>
              </View>
            )
          }
          return (
            <View key={f.key} style={styles.field}>
              <Text style={styles.label}>{f.label}</Text>
              <TextInput
                style={styles.input}
                keyboardType={f.keyboardType}
                placeholder={f.placeholder}
                value={values[f.key] ?? ''}
                onChangeText={v => setField(f.key, v)}
                placeholderTextColor="#999"
              />
            </View>
          )
        })}
      </ScrollView>
      <TouchableOpacity style={[styles.button, { marginBottom: insets.bottom + 48 }]} onPress={handleSubmit}>
        <Text style={styles.buttonText}>Opslaan</Text>
      </TouchableOpacity>
    </KeyboardAvoidingView>
  )
}

const styles = StyleSheet.create({
  container: { flex: 1, backgroundColor: '#f5f5f5' },
  scroll: { padding: 16 },
  field: { marginBottom: 12 },
  label: { fontSize: 14, fontWeight: '600', color: '#333', marginBottom: 4 },
  input: { backgroundColor: '#fff', borderRadius: 8, padding: 12, fontSize: 16, borderWidth: 1, borderColor: '#ddd' },
  computedInput: { backgroundColor: '#f0f0f0' },
  computedText: { fontSize: 16, color: '#666' },
  dateButton: { backgroundColor: '#fff', borderRadius: 8, padding: 12, borderWidth: 1, borderColor: '#ddd' },
  dateButtonText: { fontSize: 16, color: '#333' },
  button: { backgroundColor: '#4CAF50', padding: 16, borderRadius: 8, alignItems: 'center', margin: 16 },
  buttonText: { color: '#fff', fontSize: 16, fontWeight: '700' },
})