import React, { useEffect, useMemo, useState, useRef, memo } from 'react';
import { useForm, Controller } from 'react-hook-form';
import { z } from 'zod';
import { zodResolver } from '@hookform/resolvers/zod';
import { Grid, Card, CardHeader, CardContent, TextField, Switch, FormControlLabel, Box, Button, CircularProgress } from '@mui/material';
import { VehicleSelector } from './VehicleSelector';
import { DistanceInput } from './DistanceInput';
import { FuelTypeSelector } from './FuelTypeSelector';
import { UnitSystemDisplay } from './UnitSystemDisplay';
import { LocationInput } from './LocationInput';
import { CostCalculator } from './CostCalculator';
import { useFuelLogs } from '../hooks/useFuelLogs';
import { useUserSettings } from '../hooks/useUserSettings';
import { CreateFuelLogRequest, FuelType } from '../types/fuel-logs.types';

const schema = z.object({
  vehicleId: z.string().uuid(),
  dateTime: z.string().min(1),
  odometerReading: z.coerce.number().positive().optional(),
  tripDistance: z.coerce.number().positive().optional(),
  fuelType: z.nativeEnum(FuelType),
  fuelGrade: z.union([z.string(), z.null()]).optional(),
  fuelUnits: z.coerce.number().positive(),
  costPerUnit: z.coerce.number().positive(),
  locationData: z.any().optional(),
  notes: z.string().max(500).optional(),
}).refine((d) => (d.odometerReading && d.odometerReading > 0) || (d.tripDistance && d.tripDistance > 0), {
  message: 'Either odometer reading or trip distance is required'
}).refine((d) => !(d.odometerReading && d.tripDistance), {
  message: 'Cannot specify both odometer reading and trip distance'
});

const FuelLogFormComponent: React.FC<{ onSuccess?: () => void; initial?: Partial<CreateFuelLogRequest> }> = ({ onSuccess, initial }) => {
  const { userSettings } = useUserSettings();
  const { createFuelLog, isLoading } = useFuelLogs();
  const [useOdometer, setUseOdometer] = useState(false);
  const formInitialized = useRef(false);

  const { control, handleSubmit, watch, setValue, formState: { errors, isValid } } = useForm<CreateFuelLogRequest>({
    resolver: zodResolver(schema),
    mode: 'onChange',
    defaultValues: {
      dateTime: new Date().toISOString().slice(0, 16),
      fuelType: FuelType.GASOLINE,
      ...initial
    } as any
  });

  // DEBUG: Log component renders and form state
  console.log('[FuelLogForm] Render - formInitialized:', formInitialized.current, 'isLoading:', isLoading);

  // Prevent form reset after initial load
  useEffect(() => {
    if (!formInitialized.current) {
      formInitialized.current = true;
      console.log('[FuelLogForm] Form initialized');
    }
  }, []);

  // DEBUG: Watch for form value changes
  const vehicleId = watch('vehicleId');
  useEffect(() => {
    console.log('[FuelLogForm] Vehicle ID changed:', vehicleId);
  }, [vehicleId]);

  const watched = watch(['fuelUnits', 'costPerUnit']);
  const [fuelUnitsRaw, costPerUnitRaw] = watched as [string | number | undefined, string | number | undefined];

  // Convert to numbers for calculation
  const fuelUnits = typeof fuelUnitsRaw === 'string' ? parseFloat(fuelUnitsRaw) : fuelUnitsRaw;
  const costPerUnit = typeof costPerUnitRaw === 'string' ? parseFloat(costPerUnitRaw) : costPerUnitRaw;

  const calculatedCost = useMemo(() => {
    const units = fuelUnits && !isNaN(fuelUnits) ? fuelUnits : 0;
    const cost = costPerUnit && !isNaN(costPerUnit) ? costPerUnit : 0;
    return units > 0 && cost > 0 ? units * cost : 0;
  }, [fuelUnits, costPerUnit]);

  const onSubmit = async (data: CreateFuelLogRequest) => {
    const payload: CreateFuelLogRequest = {
      ...data,
      odometerReading: useOdometer ? data.odometerReading : undefined,
      tripDistance: useOdometer ? undefined : data.tripDistance,
    };
    await createFuelLog(payload);
    onSuccess?.();
  };

  useEffect(() => {
    if (useOdometer) setValue('tripDistance', undefined as any);
    else setValue('odometerReading', undefined as any);
  }, [useOdometer, setValue]);

  return (
    <Card>
      <CardHeader title="Add Fuel Log" subheader={<UnitSystemDisplay unitSystem={userSettings?.unitSystem} showLabel="Displaying in" />} />
      <CardContent>
        <form onSubmit={handleSubmit(onSubmit)}>
          <Grid container spacing={2}>
            <Grid item xs={12}>
              <Controller name="vehicleId" control={control} render={({ field }) => (
                <VehicleSelector value={field.value} onChange={field.onChange} error={errors.vehicleId?.message} required />
              )} />
            </Grid>
            <Grid item xs={12} sm={6}>
              <Controller name="dateTime" control={control} render={({ field }) => (
                <TextField {...field} label="Date & Time" type="datetime-local" fullWidth error={!!errors.dateTime} helperText={errors.dateTime?.message} InputLabelProps={{ shrink: true }} />
              )} />
            </Grid>
            <Grid item xs={12} sm={6}>
              <FormControlLabel control={<Switch checked={useOdometer} onChange={(e) => setUseOdometer(e.target.checked)} />} label={`Use ${useOdometer ? 'Odometer' : 'Trip Distance'}`} />
            </Grid>
            <Grid item xs={12} sm={6}>
              <Controller name={useOdometer ? 'odometerReading' : 'tripDistance'} control={control} render={({ field }) => (
                <DistanceInput type={useOdometer ? 'odometer' : 'trip'} value={field.value as any} onChange={field.onChange as any} unitSystem={userSettings?.unitSystem} error={useOdometer ? (errors.odometerReading?.message as any) : (errors.tripDistance?.message as any)} />
              )} />
            </Grid>
            <Grid item xs={12}>
              <Controller name="fuelType" control={control} render={({ field: fuelTypeField }) => (
                <Controller name="fuelGrade" control={control} render={({ field: fuelGradeField }) => (
                  <FuelTypeSelector fuelType={fuelTypeField.value} fuelGrade={fuelGradeField.value as any} onFuelTypeChange={fuelTypeField.onChange} onFuelGradeChange={fuelGradeField.onChange as any} error={(errors.fuelType?.message as any) || (errors.fuelGrade?.message as any)} />
                )} />
              )} />
            </Grid>
            <Grid item xs={12} sm={6}>
              <Controller name="fuelUnits" control={control} render={({ field }) => (
                <TextField
                  {...field}
                  value={field.value ?? ''}
                  onChange={(e) => field.onChange(e.target.value)}
                  label={`Fuel Amount (${userSettings?.unitSystem === 'imperial' ? 'gallons' : 'liters'})`}
                  type="number"
                  inputProps={{ step: 0.001, min: 0.001 }}
                  fullWidth
                  error={!!errors.fuelUnits}
                  helperText={errors.fuelUnits?.message}
                />
              )} />
            </Grid>
            <Grid item xs={12} sm={6}>
              <Controller name="costPerUnit" control={control} render={({ field }) => (
                <TextField
                  {...field}
                  value={field.value ?? ''}
                  onChange={(e) => field.onChange(e.target.value)}
                  label={`Cost Per ${userSettings?.unitSystem === 'imperial' ? 'Gallon' : 'Liter'}`}
                  type="number"
                  inputProps={{ step: 0.001, min: 0.001 }}
                  fullWidth
                  error={!!errors.costPerUnit}
                  helperText={errors.costPerUnit?.message}
                />
              )} />
            </Grid>
            <Grid item xs={12}>
              <CostCalculator fuelUnits={fuelUnits} costPerUnit={costPerUnit} calculatedCost={calculatedCost} unitSystem={userSettings?.unitSystem} />
            </Grid>
            <Grid item xs={12}>
              <Controller name="locationData" control={control} render={({ field }) => (
                <LocationInput value={field.value as any} onChange={field.onChange as any} placeholder="Station location (optional)" />
              )} />
            </Grid>
            <Grid item xs={12}>
              <Controller name="notes" control={control} render={({ field }) => (
                <TextField {...field} label="Notes (optional)" multiline rows={3} fullWidth error={!!errors.notes} helperText={errors.notes?.message} />
              )} />
            </Grid>
            <Grid item xs={12}>
              <Box display="flex" gap={2} justifyContent="flex-end">
                <Button type="submit" variant="contained" disabled={!isValid || isLoading} startIcon={isLoading ? <CircularProgress size={18} /> : undefined}>Add Fuel Log</Button>
              </Box>
            </Grid>
          </Grid>
        </form>
      </CardContent>
    </Card>
  );
};

export const FuelLogForm = memo(FuelLogFormComponent);