/**
 * CostView — cost trends + detail + summary.
 *
 * Features:
 * - Date range selector: Today / This month / Custom (SegmentedControl + DateInput).
 * - Recharts AreaChart showing import_cost, export_revenue, net_cost per period.
 * - Table showing per-15min periods with time, kWh values, costs, degraded badge.
 * - Summary cards: metered import/export, fixed costs, credits, total payable.
 * - "Recompute" button with confirmation.
 * - Loading/error/empty states, degraded period highlighting.
 *
 * Recharts imports are isolated to this file only.
 */

import { useState } from 'react'
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
import {
  Stack,
  Text,
  TextInput,
  Loader,
  Center,
  Alert,
  Table,
  Group,
  Badge,
  ScrollArea,
  SegmentedControl,
  Button,
  Paper,
  SimpleGrid,
  Modal,
  Title,
} from '@mantine/core'
import {
  AreaChart,
  Area,
  XAxis,
  YAxis,
  CartesianGrid,
  Tooltip,
  Legend,
  ResponsiveContainer,
} from 'recharts'
import { useEnergyCosts, useEnergyCostSummary, useRecomputeCosts } from './hooks'
import { formatLocalTime } from '../utils/datetime'
import apiClient from '../api/client'

// ---------------------------------------------------------------------------
// Cost limit — prevent accidental full-table pulls
// ---------------------------------------------------------------------------

const COSTS_MAX_LIMIT = 500

// ---------------------------------------------------------------------------
// Date range helpers
// ---------------------------------------------------------------------------

function getTodayRange(): { start: string; end: string } {
  // Use local date boundary so "today" matches what the user sees in the display.
  const now = new Date()
  const start = new Date(now.getFullYear(), now.getMonth(), now.getDate())
  const end = new Date(now.getFullYear(), now.getMonth(), now.getDate() + 1)
  return { start: start.toISOString(), end: end.toISOString() }
}

function getThisMonthRange(): { start: string; end: string } {
  // Use local date boundary so "this month" matches what the user sees in the display.
  const now = new Date()
  const start = new Date(now.getFullYear(), now.getMonth(), 1)
  const end = new Date(now.getFullYear(), now.getMonth() + 1, 1)
  return { start: start.toISOString(), end: end.toISOString() }
}

// ---------------------------------------------------------------------------
// Summary cards
// ---------------------------------------------------------------------------

interface SummaryCardProps {
  label: string
  value: string
  /** Optional secondary line, e.g. the monetary equivalent of an energy figure. */
  sub?: string
  testId?: string
}

function SummaryCard({ label, value, sub, testId }: SummaryCardProps) {
  return (
    <Paper withBorder p="sm" data-testid={testId}>
      <Stack gap={4}>
        <Text size="xs" c="dimmed">
          {label}
        </Text>
        <Text fw={600} size="lg">
          {value}
        </Text>
        {sub !== undefined && (
          <Text size="xs" c="dimmed" data-testid={testId ? `${testId}-sub` : undefined}>
            {sub}
          </Text>
        )}
      </Stack>
    </Paper>
  )
}

// ---------------------------------------------------------------------------
// CostView — main component
// ---------------------------------------------------------------------------

type RangePreset = 'today' | 'month' | 'custom'

export function CostView() {
  const [scope, setScope] = useState<'electricity' | 'thermal'>('electricity')
  if (scope === 'thermal') return <ThermalCostView onScopeChange={setScope} />
  return <ElectricityCostView onScopeChange={setScope} />
}

function ScopeSelector({ scope, onScopeChange }: { scope: 'electricity' | 'thermal'; onScopeChange: (scope: 'electricity' | 'thermal') => void }) {
  return <SegmentedControl value={scope} onChange={(value) => onScopeChange(value as 'electricity' | 'thermal')} data={[{ label: 'Electricity', value: 'electricity' }, { label: 'Thermal', value: 'thermal' }]} data-testid="costs-scope-selector" />
}

function ElectricityCostView({ onScopeChange }: { onScopeChange: (scope: 'electricity' | 'thermal') => void }) {
  const [rangePreset, setRangePreset] = useState<RangePreset>('today')
  // Date strings in YYYY-MM-DD format for custom range
  const [customStartStr, setCustomStartStr] = useState('')
  const [customEndStr, setCustomEndStr] = useState('')
  const [showRecomputeConfirm, setShowRecomputeConfirm] = useState(false)

  // Compute effective date range
  const { start, end } = (() => {
    if (rangePreset === 'today') return getTodayRange()
    if (rangePreset === 'month') return getThisMonthRange()
    return {
      start: customStartStr ? new Date(customStartStr).toISOString() : undefined,
      end: customEndStr ? new Date(customEndStr).toISOString() : undefined,
    }
  })()

  const costsQuery = useEnergyCosts(start, end, COSTS_MAX_LIMIT)
  const summaryQuery = useEnergyCostSummary(start, end)
  const recomputeMutation = useRecomputeCosts()

  async function handleRecompute() {
    setShowRecomputeConfirm(false)
    await recomputeMutation.mutateAsync({ start, end })
  }

  // ---------------------------------------------------------------------------
  // Render
  // ---------------------------------------------------------------------------

  const currency = costsQuery.data?.items[0]?.currency ?? summaryQuery.data?.currency ?? 'EUR'

  return (
    <Stack gap="lg" data-testid="cost-view">
      {/* Date range selector */}
      <Group align="flex-start" gap="md" wrap="wrap">
        <ScopeSelector scope="electricity" onScopeChange={onScopeChange} />
        <Stack gap="xs">
          <Text size="sm" fw={500}>
            Date range
          </Text>
          <SegmentedControl
            value={rangePreset}
            onChange={(v) => setRangePreset(v as RangePreset)}
            data={[
              { label: 'Today', value: 'today' },
              { label: 'This month', value: 'month' },
              { label: 'Custom', value: 'custom' },
            ]}
            data-testid="cost-range-control"
          />
        </Stack>

        {rangePreset === 'custom' && (
          <Group gap="sm" align="flex-end">
            <TextInput
              label="From"
              type="date"
              value={customStartStr}
              onChange={(e) => setCustomStartStr(e.currentTarget.value)}
              data-testid="cost-custom-start"
            />
            <TextInput
              label="To"
              type="date"
              value={customEndStr}
              onChange={(e) => setCustomEndStr(e.currentTarget.value)}
              data-testid="cost-custom-end"
            />
          </Group>
        )}

        <Group gap="sm" style={{ marginLeft: 'auto' }} align="flex-end">
          <Button
            variant="outline"
            color="orange"
            size="sm"
            onClick={() => setShowRecomputeConfirm(true)}
            loading={recomputeMutation.isPending}
            data-testid="cost-recompute-button"
          >
            Recompute
          </Button>
        </Group>
      </Group>

      {/* Summary cards */}
      {summaryQuery.isLoading && (
        <Center>
          <Loader size="sm" />
        </Center>
      )}

      {summaryQuery.isError && (
        <Alert color="red" data-testid="summary-error">
          Failed to load cost summary.
        </Alert>
      )}

      {summaryQuery.data && (
        <Stack gap="xs">
          <Title order={6} c="dimmed">
            Summary
          </Title>
          <SimpleGrid cols={{ base: 2, sm: 3 }} spacing="sm" data-testid="cost-summary">
            <SummaryCard
              label="Import (kWh)"
              value={summaryQuery.data.metered_import_kwh.toFixed(3)}
              sub={`${summaryQuery.data.metered_import.toFixed(2)} ${currency}`}
              testId="summary-import"
            />
            <SummaryCard
              label="Export (kWh)"
              value={summaryQuery.data.metered_export_kwh.toFixed(3)}
              sub={`${summaryQuery.data.metered_export.toFixed(2)} ${currency}`}
              testId="summary-export"
            />
            <SummaryCard
              label={`Fixed costs (${currency})`}
              value={summaryQuery.data.fixed_costs.toFixed(2)}
              testId="summary-fixed"
            />
            <SummaryCard
              label={`Credits (${currency})`}
              value={summaryQuery.data.credits.toFixed(2)}
              testId="summary-credits"
            />
            <SummaryCard
              label={`Total payable (${currency})`}
              value={summaryQuery.data.total_payable.toFixed(2)}
              testId="summary-total"
            />
          </SimpleGrid>
        </Stack>
      )}

      {/* Cost chart */}
      {costsQuery.isLoading && (
        <Center py="xl" data-testid="costs-loading">
          <Loader />
        </Center>
      )}

      {costsQuery.isError && (
        <Alert color="red" data-testid="costs-error">
          Failed to load cost periods. Please refresh.
        </Alert>
      )}

      {costsQuery.data && costsQuery.data.items.length === 0 && (
        <Alert color="gray" data-testid="costs-empty">
          No cost data available for the selected period.
        </Alert>
      )}

      {costsQuery.data && costsQuery.data.items.length > 0 && (
        <>
          {/* Area chart */}
          <Stack gap="xs" data-testid="cost-chart">
            <Title order={6} c="dimmed">
              Cost trends ({currency})
            </Title>
            <ResponsiveContainer width="100%" height={220}>
              <AreaChart
                data={costsQuery.data.items.map((item) => ({
                  time: formatLocalTime(item.period_start),
                  import_cost: item.import_cost,
                  export_revenue: item.export_revenue,
                  net_cost: item.net_cost,
                }))}
                margin={{ top: 4, right: 16, left: 0, bottom: 4 }}
              >
                <CartesianGrid strokeDasharray="3 3" />
                <XAxis dataKey="time" tick={{ fontSize: 10 }} interval="preserveStartEnd" />
                <YAxis tick={{ fontSize: 10 }} tickFormatter={(v: number) => v.toFixed(2)} />
                <Tooltip
                  // eslint-disable-next-line @typescript-eslint/no-explicit-any
                  formatter={(val: any) =>
                    [`${typeof val === 'number' ? val.toFixed(4) : String(val)} ${currency}`, undefined]
                  }
                />
                <Legend />
                <Area
                  type="monotone"
                  dataKey="import_cost"
                  stroke="#2196f3"
                  fill="#bbdefb"
                  name="Import cost"
                  dot={false}
                />
                <Area
                  type="monotone"
                  dataKey="export_revenue"
                  stroke="#4caf50"
                  fill="#c8e6c9"
                  name="Export revenue"
                  dot={false}
                />
                <Area
                  type="monotone"
                  dataKey="net_cost"
                  stroke="#ff9800"
                  fill="#ffe0b2"
                  name="Net cost"
                  dot={false}
                />
              </AreaChart>
            </ResponsiveContainer>
          </Stack>

          {/* Detail table */}
          <Stack gap="xs">
            <Title order={6} c="dimmed">
              Period detail
            </Title>
            <ScrollArea>
              <Table
                striped
                highlightOnHover
                withTableBorder
                withColumnBorders
                style={{ fontSize: 12 }}
                data-testid="costs-table"
              >
                <Table.Thead>
                  <Table.Tr>
                    <Table.Th>Time</Table.Th>
                    <Table.Th>Import kWh</Table.Th>
                    <Table.Th>Export kWh</Table.Th>
                    <Table.Th>Import cost</Table.Th>
                    <Table.Th>Export rev.</Table.Th>
                    <Table.Th>Net cost</Table.Th>
                    <Table.Th></Table.Th>
                  </Table.Tr>
                </Table.Thead>
                <Table.Tbody>
                  {costsQuery.data.items.map((item, idx) => (
                    <Table.Tr
                      key={idx}
                      style={item.degraded ? { opacity: 0.6 } : undefined}
                      data-testid={`cost-row-${idx}`}
                    >
                      <Table.Td>
                        <Text size="xs">
                          {formatLocalTime(item.period_start)}
                        </Text>
                      </Table.Td>
                      <Table.Td>{(item.d1_kwh + item.d2_kwh).toFixed(3)}</Table.Td>
                      <Table.Td>{(item.r1_kwh + item.r2_kwh).toFixed(3)}</Table.Td>
                      <Table.Td>{item.import_cost.toFixed(4)}</Table.Td>
                      <Table.Td>{item.export_revenue.toFixed(4)}</Table.Td>
                      <Table.Td>{item.net_cost.toFixed(4)}</Table.Td>
                      <Table.Td>
                        {item.degraded && (
                          <Badge color="orange" size="xs" data-testid={`cost-degraded-${idx}`}>
                            degraded
                          </Badge>
                        )}
                      </Table.Td>
                    </Table.Tr>
                  ))}
                </Table.Tbody>
              </Table>
            </ScrollArea>
          </Stack>
        </>
      )}

      {/* Recompute confirmation modal */}
      {showRecomputeConfirm && (
        <Modal
          opened
          onClose={() => setShowRecomputeConfirm(false)}
          title="Recompute costs?"
          size="sm"
          data-testid="recompute-confirm-modal"
        >
          <Stack gap="md">
            <Text size="sm">
              This will recompute all cost periods for the selected date range. Continue?
            </Text>
            <Group justify="flex-end" gap="sm">
              <Button
                variant="default"
                onClick={() => setShowRecomputeConfirm(false)}
                data-testid="recompute-cancel"
              >
                Cancel
              </Button>
              <Button
                color="orange"
                onClick={handleRecompute}
                data-testid="recompute-confirm"
              >
                Recompute
              </Button>
            </Group>
          </Stack>
        </Modal>
      )}
    </Stack>
  )
}

function ThermalCostView({ onScopeChange }: { onScopeChange: (scope: 'electricity' | 'thermal') => void }) {
  const [rangePreset, setRangePreset] = useState<RangePreset>('today')
  const [customStartStr, setCustomStartStr] = useState('')
  const [customEndStr, setCustomEndStr] = useState('')
  const [showConfirm, setShowConfirm] = useState(false)
  const [recomputeError, setRecomputeError] = useState<string | null>(null)
  const [recomputeSuccess, setRecomputeSuccess] = useState<string | null>(null)
  const [expandedRows, setExpandedRows] = useState<Set<number>>(() => new Set())
  const [ledgerOffset, setLedgerOffset] = useState(0)
  const { start, end } = (() => {
    if (rangePreset === 'today') return getTodayRange()
    if (rangePreset === 'month') return getThisMonthRange()
    return {
      start: customStartStr ? new Date(customStartStr).toISOString() : undefined,
      end: customEndStr ? new Date(customEndStr).toISOString() : undefined,
    }
  })()
  // The server only accepts complete UTC quarters. Never send a future end.
  const closedEnd = (() => {
    const now = new Date()
    now.setUTCMinutes(Math.floor(now.getUTCMinutes() / 15) * 15, 0, 0)
    const selectedEnd = end ? new Date(end) : now
    return new Date(Math.min(selectedEnd.getTime(), now.getTime())).toISOString()
  })()
  const recomputeStart = start
  const recomputeAvailable = !!recomputeStart && new Date(recomputeStart) < new Date(closedEnd)
  const qc = useQueryClient()
  const resetLedgerPage = () => {
    setLedgerOffset(0)
    setExpandedRows(new Set())
  }
  const rows = useQuery({ queryKey: ['meter-costs', 'thermal', start, end, ledgerOffset], queryFn: async () => {
    const result = await apiClient.GET('/api/energy/meter-costs', { params: { query: { scope: 'thermal', start, end, limit: COSTS_MAX_LIMIT, offset: ledgerOffset } } })
    return result.data
  } })
  const meters = useQuery({ queryKey: ['energy-meters', 'thermal'], queryFn: async () => {
    const result = await apiClient.GET('/api/energy/meters')
    return result.data
  } })
  const summary = useQuery({ queryKey: ['meter-cost-summary', 'thermal', start, end], queryFn: async () => {
    const result = await apiClient.GET('/api/energy/meter-costs/summary', { params: { query: { scope: 'thermal', start, end } } })
    return result.data
  } })
  const recompute = useMutation({ mutationFn: () => apiClient.POST('/api/energy/meter-costs/recompute', { params: { query: { scope: 'thermal', start: recomputeStart!, end: closedEnd } } }), onSuccess: (result) => {
    void qc.invalidateQueries({ queryKey: ['meter-costs', 'thermal'] }); void qc.invalidateQueries({ queryKey: ['meter-cost-summary', 'thermal'] })
    setRecomputeSuccess(`Recomputed ${result.data?.processed ?? 0} closed periods.`)
  } })
  const currency = summary.data?.currency ?? rows.data?.items[0]?.currency ?? 'EUR'
  const fixed = summary.data?.fixed_breakdown
  const hasCurrentHeatingMeter = meters.data?.items.some((meter) => meter.commodity === 'heating' && meter.ended_at === null)
  const hasCurrentHotWaterMeter = meters.data?.items.some((meter) => meter.commodity === 'hot_water' && meter.ended_at === null)
  const missingCurrentMeters = [
    ...(hasCurrentHeatingMeter === false ? ['heating'] : []),
    ...(hasCurrentHotWaterMeter === false ? ['hot-water'] : []),
  ]
  const totalRows = rows.data?.total ?? 0
  const shownStart = totalRows === 0 ? 0 : ledgerOffset + 1
  const shownEnd = Math.min(ledgerOffset + (rows.data?.items.length ?? 0), totalRows)
  return <Stack gap="lg" data-testid="thermal-cost-view">
    <Group align="flex-start" gap="md" wrap="wrap"><ScopeSelector scope="thermal" onScopeChange={onScopeChange} /><Stack gap="xs"><Text size="sm" fw={500}>Date range</Text><SegmentedControl value={rangePreset} onChange={(value) => { resetLedgerPage(); setRangePreset(value as RangePreset) }} data={[{ label: 'Today', value: 'today' }, { label: 'This month', value: 'month' }, { label: 'Custom', value: 'custom' }]} data-testid="thermal-cost-range-control" /></Stack>{rangePreset === 'custom' && <Group gap="sm" align="flex-end"><TextInput label="From" type="date" value={customStartStr} onChange={(event) => { resetLedgerPage(); setCustomStartStr(event.currentTarget.value) }} data-testid="thermal-cost-custom-start" /><TextInput label="To" type="date" value={customEndStr} onChange={(event) => { resetLedgerPage(); setCustomEndStr(event.currentTarget.value) }} data-testid="thermal-cost-custom-end" /></Group>}<Button variant="outline" color="orange" onClick={() => { setRecomputeError(null); setRecomputeSuccess(null); setShowConfirm(true) }} disabled={!recomputeAvailable} data-testid="thermal-recompute-button">Recompute</Button></Group>
    {(rows.isLoading || summary.isLoading) && <Center><Loader size="sm" /></Center>}
    {(rows.isError || summary.isError) && <Alert color="red">Failed to load thermal costs.</Alert>}
    {recomputeError && <Alert color="red" data-testid="thermal-recompute-error">{recomputeError}</Alert>}
    {recomputeSuccess && <Alert color="green" data-testid="thermal-recompute-success">{recomputeSuccess}</Alert>}
    {summary.data && <Stack gap="xs" data-testid="thermal-cost-summary"><Title order={6}>{rangePreset === 'today' ? 'Today' : rangePreset === 'month' ? 'This month' : 'Custom range'} ({currency})</Title><Text size="sm" data-testid="thermal-cost-range">{start ?? 'Select a start date'} — {end ?? 'Select an end date'}</Text><SimpleGrid cols={{ base: 2, sm: 3 }}>
      <SummaryCard label="Heating" value={hasCurrentHeatingMeter === false ? 'Not configured' : summary.data.heating} /><SummaryCard label="Hot-water heating" value={hasCurrentHotWaterMeter === false ? 'Not configured' : summary.data.hot_water_heating} /><SummaryCard label="Hot water" value={hasCurrentHotWaterMeter === false ? 'Not configured' : summary.data.hot_water} /><SummaryCard label="Hot-water tax" value={hasCurrentHotWaterMeter === false ? 'Not configured' : summary.data.hot_water_tax} /><SummaryCard label="Variable subtotal" value={summary.data.variable_subtotal} /><SummaryCard label="Fixed subtotal" value={summary.data.fixed_subtotal} /><SummaryCard label="All-in total" value={summary.data.all_in} />
    </SimpleGrid>{missingCurrentMeters.length > 0 && <Alert color="yellow" data-testid="thermal-missing-current-meter">Current {missingCurrentMeters.join(' and ')} meter{missingCurrentMeters.length > 1 ? 's are' : ' is'} not configured. Historical ledger rows do not establish a current meter.</Alert>}<Text size="sm" data-testid="thermal-period-count">{summary.data.period_count} periods; {summary.data.degraded_count} degraded</Text>{summary.data.degraded_count > 0 && <Alert color="orange" data-testid="thermal-summary-degraded">Some totals include degraded periods. Expand a row to see its recorded reason.</Alert>}{fixed && <Text size="sm" data-testid="thermal-fixed-breakdown">Fixed once per settled local day (summary only): {Object.entries(fixed).map(([key, value]) => `${key} ${value}`).join(' · ')}</Text>}</Stack>}
    {rows.data?.items.length === 0 && <Alert color="gray" data-testid="thermal-costs-empty">No thermal cost data for this range. Check that heating or hot-water meters are bound and have settled readings.</Alert>}
    {rows.data && <Stack gap="xs"><Text size="sm" c="dimmed" data-testid="thermal-ledger-count">Showing {shownStart}-{shownEnd} of {totalRows}</Text>{rows.data.items.length > 0 && <ScrollArea><Table striped withTableBorder data-testid="thermal-costs-table"><Table.Thead><Table.Tr><Table.Th>Time</Table.Th><Table.Th>Commodity</Table.Th><Table.Th>Quantity</Table.Th><Table.Th>Cost</Table.Th><Table.Th>Breakdown</Table.Th><Table.Th>Status</Table.Th><Table.Th></Table.Th></Table.Tr></Table.Thead><Table.Tbody>{rows.data.items.flatMap((item, index) => [<Table.Tr key={`${item.commodity}-${item.period_start}`} data-testid={`thermal-cost-row-${index}`}><Table.Td>{formatLocalTime(item.period_start)}</Table.Td><Table.Td>{item.commodity}</Table.Td><Table.Td>{item.quantity}</Table.Td><Table.Td>{item.cost} {item.currency}</Table.Td><Table.Td>{Object.entries(item.cost_breakdown).map(([key, value]) => `${key} ${value}`).join(', ')}</Table.Td><Table.Td>{item.degraded ? <Badge color="orange" data-testid={`thermal-degraded-${index}`}>{item.degraded_reason ?? 'degraded'}</Badge> : 'normal'}</Table.Td><Table.Td><Button size="xs" variant="subtle" onClick={() => setExpandedRows((current) => { const next = new Set(current); if (next.has(index)) next.delete(index); else next.add(index); return next })} data-testid={`thermal-cost-expand-${index}`}>{expandedRows.has(index) ? 'Hide audit' : 'Audit'}</Button></Table.Td></Table.Tr>, ...(expandedRows.has(index) ? [<Table.Tr key={`audit-${item.commodity}-${item.period_start}`} data-testid={`thermal-cost-audit-${index}`}><Table.Td colSpan={7}><Text size="xs">Contract version: {item.contract_version_id ?? 'none'}</Text><Text size="xs">Pricing snapshot: {JSON.stringify(item.pricing_snapshot)}</Text></Table.Td></Table.Tr>] : [])])}</Table.Tbody></Table></ScrollArea>}<Group justify="flex-end"><Button size="xs" variant="default" disabled={ledgerOffset === 0} onClick={() => { setExpandedRows(new Set()); setLedgerOffset((current) => Math.max(0, current - COSTS_MAX_LIMIT)) }} data-testid="thermal-ledger-prev">Previous</Button><Button size="xs" variant="default" disabled={ledgerOffset + (rows.data.items.length ?? 0) >= totalRows} onClick={() => { setExpandedRows(new Set()); setLedgerOffset((current) => current + COSTS_MAX_LIMIT) }} data-testid="thermal-ledger-next">Next</Button></Group></Stack>}
    {showConfirm && <Modal opened onClose={() => setShowConfirm(false)} title="Recompute thermal costs?" data-testid="thermal-recompute-confirm-modal"><Stack><Text>This explicitly overwrites closed 15-minute thermal ledger rows for {recomputeStart ?? 'the selected start'} — {closedEnd}. Continue?</Text>{!recomputeAvailable && <Alert color="yellow">Select a range containing at least one closed UTC quarter.</Alert>}<Group justify="flex-end"><Button variant="default" onClick={() => setShowConfirm(false)} data-testid="thermal-recompute-cancel">Cancel</Button><Button color="orange" loading={recompute.isPending} disabled={!recomputeAvailable} onClick={async () => { try { await recompute.mutateAsync(); setShowConfirm(false) } catch { setRecomputeError('Failed to recompute thermal costs. Please try again.'); setShowConfirm(false) } }} data-testid="thermal-recompute-confirm">Recompute</Button></Group></Stack></Modal>}
  </Stack>
}