/**
 * ContractManager — energy contract list UI.
 *
 * Features:
 * - Table of contracts: name, kind, active badge, currency, created date, actions.
 * - Actions per row: Activate (PATCH active=true), Add Version, View History.
 * - "New Contract" button at top.
 * - Version history modal showing all versions with effective dates and values.
 * - Loading / error / empty states.
 */

import { useState } from 'react'
import {
  Table,
  Button,
  Group,
  Text,
  Loader,
  Center,
  Alert,
  Stack,
  Badge,
  ScrollArea,
  Modal,
  Accordion,
  Code,
} from '@mantine/core'
import {
  useContracts,
  useUpdateContract,
  type ContractResponse,
  type ContractDetailResponse,
} from './hooks'
import { ContractForm } from './ContractForm'
import apiClient from '../api/client'
import { formatLocalDate } from '../utils/datetime'

// ---------------------------------------------------------------------------
// Version history modal
// ---------------------------------------------------------------------------

interface VersionHistoryModalProps {
  contractId: number
  contractName: string
  onClose: () => void
}

function VersionHistoryModal({ contractId, contractName, onClose }: VersionHistoryModalProps) {
  const [loading, setLoading] = useState(true)
  const [detail, setDetail] = useState<ContractDetailResponse | null>(null)
  const [fetchError, setFetchError] = useState<string | null>(null)

  // Fetch detail on first render
  useState(() => {
    apiClient
      .GET('/api/energy/contracts/{contract_id}', {
        params: { path: { contract_id: contractId } },
      })
      .then((res) => {
        setDetail(res.data ?? null)
        setLoading(false)
      })
      .catch(() => {
        setFetchError('Failed to load contract details.')
        setLoading(false)
      })
  })

  return (
    <Modal
      opened
      onClose={onClose}
      title={`Version history — ${contractName}`}
      size="lg"
      data-testid="version-history-modal"
    >
      {loading && (
        <Center py="md">
          <Loader size="sm" />
        </Center>
      )}
      {fetchError && (
        <Alert color="red" data-testid="version-history-error">
          {fetchError}
        </Alert>
      )}
      {!loading && !fetchError && detail && (
        <>
          {detail.versions.length === 0 ? (
            <Text c="dimmed" ta="center" size="sm" data-testid="version-history-empty">
              No versions found.
            </Text>
          ) : (
            <Accordion variant="separated" data-testid="version-history-accordion">
              {detail.versions.map((v) => (
                <Accordion.Item key={v.id} value={String(v.id)} data-testid={`version-item-${v.id}`}>
                  <Accordion.Control>
                    <Group gap="sm">
                      <Text size="sm" fw={500}>
                        From: {formatLocalDate(v.effective_from)}
                      </Text>
                      {v.effective_to ? (
                        <Text size="xs" c="dimmed">
                          To: {formatLocalDate(v.effective_to)}
                        </Text>
                      ) : (
                        <Badge color="green" size="xs">
                          current
                        </Badge>
                      )}
                    </Group>
                  </Accordion.Control>
                  <Accordion.Panel>
                    <Code block style={{ fontSize: 11 }}>
                      {JSON.stringify(v.values, null, 2)}
                    </Code>
                  </Accordion.Panel>
                </Accordion.Item>
              ))}
            </Accordion>
          )}
        </>
      )}
      <Group justify="flex-end" mt="md">
        <Button variant="default" onClick={onClose}>
          Close
        </Button>
      </Group>
    </Modal>
  )
}

// ---------------------------------------------------------------------------
// Contract table
// ---------------------------------------------------------------------------

interface ContractTableProps {
  contracts: ContractResponse[]
  onActivate: (id: number) => void
  onAddVersion: (contract: ContractResponse) => void
  onViewHistory: (contract: ContractResponse) => void
  activatingId: number | null
}

function ContractTable({
  contracts,
  onActivate,
  onAddVersion,
  onViewHistory,
  activatingId,
}: ContractTableProps) {
  if (contracts.length === 0) {
    return (
      <Text c="dimmed" ta="center" size="sm" data-testid="contracts-empty">
        No contracts configured yet. Click "New Contract" to add one.
      </Text>
    )
  }

  return (
    <ScrollArea>
      <Table striped highlightOnHover withTableBorder data-testid="contracts-table">
        <Table.Thead>
          <Table.Tr>
            <Table.Th>Name</Table.Th>
            <Table.Th>Kind</Table.Th>
            <Table.Th>Active</Table.Th>
            <Table.Th>Currency</Table.Th>
            <Table.Th>Created</Table.Th>
            <Table.Th style={{ textAlign: 'right' }}>Actions</Table.Th>
          </Table.Tr>
        </Table.Thead>
        <Table.Tbody>
          {contracts.map((contract) => (
            <Table.Tr key={contract.id} data-testid={`contract-row-${contract.id}`}>
              <Table.Td>
                <Text fw={500} size="sm">
                  {contract.name}
                </Text>
              </Table.Td>
              <Table.Td>
                <Badge variant="outline" size="sm">
                  {contract.kind}
                </Badge>
              </Table.Td>
              <Table.Td>
                <Badge
                  color={contract.active ? 'green' : 'gray'}
                  variant="light"
                  size="sm"
                  data-testid={`contract-active-badge-${contract.id}`}
                >
                  {contract.active ? 'active' : 'inactive'}
                </Badge>
              </Table.Td>
              <Table.Td>{contract.currency}</Table.Td>
              <Table.Td>
                <Text size="xs" c="dimmed">
                  {formatLocalDate(contract.created_at)}
                </Text>
              </Table.Td>
              <Table.Td>
                <Group justify="flex-end" gap="xs">
                  {!contract.active && (
                    <Button
                      size="xs"
                      variant="outline"
                      color="green"
                      loading={activatingId === contract.id}
                      onClick={() => onActivate(contract.id)}
                      data-testid={`contract-activate-${contract.id}`}
                    >
                      Activate
                    </Button>
                  )}
                  <Button
                    size="xs"
                    variant="outline"
                    onClick={() => onAddVersion(contract)}
                    data-testid={`contract-add-version-${contract.id}`}
                  >
                    Add Version
                  </Button>
                  <Button
                    size="xs"
                    variant="subtle"
                    onClick={() => onViewHistory(contract)}
                    data-testid={`contract-history-${contract.id}`}
                  >
                    History
                  </Button>
                </Group>
              </Table.Td>
            </Table.Tr>
          ))}
        </Table.Tbody>
      </Table>
    </ScrollArea>
  )
}

// ---------------------------------------------------------------------------
// ContractManager — top-level
// ---------------------------------------------------------------------------

export function ContractManager() {
  const contractsQuery = useContracts()
  const updateMutation = useUpdateContract()

  const [showCreateForm, setShowCreateForm] = useState(false)
  const [addVersionContract, setAddVersionContract] = useState<ContractResponse | null>(null)
  const [historyContract, setHistoryContract] = useState<ContractResponse | null>(null)
  const [activatingId, setActivatingId] = useState<number | null>(null)

  async function handleActivate(id: number) {
    setActivatingId(id)
    try {
      await updateMutation.mutateAsync({ id, body: { active: true } })
    } finally {
      setActivatingId(null)
    }
  }

  // ---------------------------------------------------------------------------
  // Render states
  // ---------------------------------------------------------------------------

  if (contractsQuery.isLoading) {
    return (
      <Center py="xl" data-testid="contracts-loading">
        <Loader />
      </Center>
    )
  }

  if (contractsQuery.isError || !contractsQuery.data) {
    return (
      <Alert color="red" data-testid="contracts-load-error">
        Failed to load contracts. Please refresh.
      </Alert>
    )
  }

  const contracts = contractsQuery.data.items

  return (
    <Stack gap="lg" data-testid="contract-manager">
      <Group justify="space-between" align="center">
        <Text fw={500}>Energy Contracts</Text>
        <Button onClick={() => setShowCreateForm(true)} data-testid="contract-new-button">
          New Contract
        </Button>
      </Group>

      <ContractTable
        contracts={contracts}
        onActivate={handleActivate}
        onAddVersion={(c) => setAddVersionContract(c)}
        onViewHistory={(c) => setHistoryContract(c)}
        activatingId={activatingId}
      />

      {/* Create new contract */}
      {showCreateForm && (
        <ContractForm
          onClose={() => setShowCreateForm(false)}
          onSaved={() => setShowCreateForm(false)}
        />
      )}

      {/* Add version to existing contract */}
      {addVersionContract && (
        <ContractForm
          contractId={addVersionContract.id}
          defaultKind={addVersionContract.kind}
          onClose={() => setAddVersionContract(null)}
          onSaved={() => setAddVersionContract(null)}
        />
      )}

      {/* Version history modal */}
      {historyContract && (
        <VersionHistoryModal
          contractId={historyContract.id}
          contractName={historyContract.name}
          onClose={() => setHistoryContract(null)}
        />
      )}
    </Stack>
  )
}