import { Box, Text, useInput, useStdout } from '@hermes/ink'
import { useEffect, useMemo, useState } from 'react'

import { providerDisplayNames } from '../domain/providers.js'
import { TUI_SESSION_MODEL_FLAG } from '../domain/slash.js'
import type { GatewayClient } from '../gatewayClient.js'
import type { ModelOptionProvider, ModelOptionsResponse } from '../gatewayTypes.js'
import { fuzzyRank } from '../lib/fuzzy.js'
import { asRpcResult, rpcErrorMessage } from '../lib/rpc.js'
import type { Theme } from '../theme.js'

import { OverlayHint, useOverlayKeys, windowItems } from './overlayControls.js'

const VISIBLE = 12
const MIN_WIDTH = 40
const MAX_WIDTH = 90

type Stage = 'provider' | 'key' | 'model' | 'disconnect'

type ProviderRow = { name: string; provider: ModelOptionProvider }

export function providerIndexAfterClearingFilter(providerRows: ProviderRow[], provider: ModelOptionProvider | undefined) {
  if (!provider) {
    return -1
  }

  return providerRows.findIndex(row => row.provider.slug === provider.slug)
}

export function ModelPicker({
  allowPersistGlobal = true,
  gw,
  initialRefresh = false,
  onCancel,
  onSelect,
  sessionId,
  t
}: ModelPickerProps) {
  const [providers, setProviders] = useState<ModelOptionProvider[]>([])
  const [currentModel, setCurrentModel] = useState('')
  const [err, setErr] = useState('')
  const [loading, setLoading] = useState(true)
  const [persistGlobal, setPersistGlobal] = useState(false)
  const [providerIdx, setProviderIdx] = useState(0)
  const [modelIdx, setModelIdx] = useState(0)
  const [stage, setStage] = useState<Stage>('provider')
  const [keyInput, setKeyInput] = useState('')
  const [keySaving, setKeySaving] = useState(false)
  const [keyError, setKeyError] = useState('')
  // Type-to-filter query, scoped per stage (cleared on stage change).
  const [filter, setFilter] = useState('')

  const { stdout } = useStdout()
  // Pin the picker to a stable width so the FloatBox parent (which shrinks-
  // to-fit with alignSelf="flex-start") doesn't resize as long provider /
  // model names scroll into view, and so `wrap="truncate-end"` on each row
  // has an actual constraint to truncate against.
  const width = Math.max(MIN_WIDTH, Math.min(MAX_WIDTH, (stdout?.columns ?? 80) - 6))

  useEffect(() => {
    gw.request<ModelOptionsResponse>('model.options', {
      ...(sessionId ? { session_id: sessionId } : {}),
      ...(initialRefresh ? { refresh: true } : {}),
      // The TUI picker shows the full provider universe with setup
      // affordances ("paste KEY to activate"), so opt into unconfigured
      // rows — the backend now defaults to the configured subset for
      // desktop chat pickers (#56974).
      include_unconfigured: true
    })
      .then(raw => {
        const r = asRpcResult<ModelOptionsResponse>(raw)

        if (!r) {
          setErr('invalid response: model.options')
          setLoading(false)

          return
        }

        const next = r.providers ?? []
        setProviders(next)
        setCurrentModel(String(r.model ?? ''))
        setProviderIdx(
          Math.max(
            0,
            next.findIndex(p => p.is_current)
          )
        )
        setModelIdx(0)
        setStage('provider')
        setErr('')
        setLoading(false)
      })
      .catch((e: unknown) => {
        setErr(rpcErrorMessage(e))
        setLoading(false)
      })
  }, [gw, initialRefresh, sessionId])

  const names = useMemo(() => providerDisplayNames(providers), [providers])

  // Provider rows carry their display name so fuzzy filtering can match on
  // name + slug while keeping the name/provider pairing intact across ranking.
  const providerRows = useMemo(
    () => providers.map((p, i) => ({ provider: p, name: names[i] ?? p.name ?? p.slug })),
    [providers, names]
  )

  // providerIdx / modelIdx always index into the *displayed* (filtered) lists.
  // With an empty filter the filtered list equals the full list, so navigation
  // behaves exactly as before. Filtering only applies on the relevant stage.
  const filteredProviderRows = useMemo(() => {
    if (stage !== 'provider' || !filter.trim()) {
      return providerRows
    }

    return fuzzyRank(
      providerRows,
      filter,
      row => `${row.name} ${row.provider.slug} ${(row.provider.models ?? []).join(' ')}`
    ).map(r => r.item)
  }, [providerRows, filter, stage])

  const provider = filteredProviderRows[providerIdx]?.provider
  const allModels = useMemo(() => provider?.models ?? [], [provider])

  const filteredModels = useMemo(() => {
    if (stage !== 'model' || !filter.trim()) {
      return allModels
    }

    return fuzzyRank(allModels, filter, m => m).map(r => r.item)
  }, [allModels, filter, stage])

  const models = filteredModels

  // Keep the active selection within the (possibly filtered) list bounds.
  useEffect(() => {
    if (providerIdx >= filteredProviderRows.length && filteredProviderRows.length > 0) {
      setProviderIdx(0)
    }
  }, [filteredProviderRows.length, providerIdx])

  useEffect(() => {
    if (modelIdx >= models.length && models.length > 0) {
      setModelIdx(0)
    }
  }, [models.length, modelIdx])

  const back = () => {
    // Esc first clears an active filter on the list stages, before navigating.
    if ((stage === 'provider' || stage === 'model') && filter.trim()) {
      // Preserve the selected provider across filter clear (same fix as
      // Enter→key/model and Ctrl+D transitions above).
      const fullProviderIdx = providerIndexAfterClearingFilter(providerRows, provider)

      if (fullProviderIdx >= 0) {
        setProviderIdx(fullProviderIdx)
      } else if (stage === 'provider') {
        setProviderIdx(0)
      }

      setFilter('')
      setModelIdx(0)

      return
    }

    if (stage === 'model' || stage === 'key' || stage === 'disconnect') {
      setStage('provider')
      setModelIdx(0)
      setKeyInput('')
      setKeyError('')
      setKeySaving(false)
      setFilter('')

      return
    }

    onCancel()
  }

  // On the list stages we capture printable keys (including 'q') into the
  // filter, so the shared overlay q/Esc handler must yield to our own handler.
  const listStage = stage === 'provider' || stage === 'model'
  useOverlayKeys({ disabled: listStage, onBack: back, onClose: onCancel })

  useInput((ch, key) => {
    // Key entry stage handles its own input
    if (stage === 'key') {
      if (keySaving) {
        return
      }

      if (key.return) {
        if (!keyInput.trim()) {
          return
        }

        setKeySaving(true)
        setKeyError('')
        gw.request<{ provider?: ModelOptionProvider }>('model.save_key', {
          slug: provider?.slug,
          api_key: keyInput.trim(),
          ...(sessionId ? { session_id: sessionId } : {})
        })
          .then(raw => {
            const r = asRpcResult<{ provider?: ModelOptionProvider }>(raw)

            if (!r?.provider) {
              setKeyError('failed to save key')
              setKeySaving(false)

              return
            }

            // Update the provider in our list with fresh data
            setProviders(prev => prev.map(p => (p.slug === r.provider!.slug ? r.provider! : p)))
            setKeyInput('')
            setKeySaving(false)
            setStage('model')
            setModelIdx(0)
          })
          .catch((e: unknown) => {
            setKeyError(rpcErrorMessage(e))
            setKeySaving(false)
          })

        return
      }

      if (key.backspace || key.delete) {
        setKeyInput(v => v.slice(0, -1))

        return
      }

      // ctrl+u clears input
      if (ch === '\u0015') {
        setKeyInput('')

        return
      }

      if (ch && !key.ctrl && !key.meta) {
        setKeyInput(v => v + ch)
      }

      return
    }

    // Disconnect confirmation stage
    if (stage === 'disconnect') {
      if (ch.toLowerCase() === 'y' || key.return) {
        if (!provider) {
          setStage('provider')

          return
        }

        setKeySaving(true)
        gw.request<{ disconnected?: boolean }>('model.disconnect', {
          slug: provider.slug,
          ...(sessionId ? { session_id: sessionId } : {})
        })
          .then(raw => {
            const r = asRpcResult<{ disconnected?: boolean }>(raw)

            if (r?.disconnected) {
              // Mark provider as unauthenticated in local state
              setProviders(prev =>
                prev.map(p =>
                  p.slug === provider.slug
                    ? {
                        ...p,
                        authenticated: false,
                        models: [],
                        total_models: 0,
                        warning: p.key_env ? `paste ${p.key_env} to activate` : 'run `hermes model` to configure'
                      }
                    : p
                )
              )
            }

            setKeySaving(false)
            setStage('provider')
          })
          .catch(() => {
            setKeySaving(false)
            setStage('provider')
          })

        return
      }

      if (ch.toLowerCase() === 'n' || key.escape) {
        setStage('provider')

        return
      }

      return
    }

    // List-stage Esc/q handling (overlay keys are disabled while on a list
    // stage so 'q' can be typed into the filter).
    if (key.escape) {
      back()

      return
    }

    if (ch === 'q' && !filter) {
      onCancel()

      return
    }

    const count = stage === 'provider' ? filteredProviderRows.length : models.length
    const sel = stage === 'provider' ? providerIdx : modelIdx
    const setSel = stage === 'provider' ? setProviderIdx : setModelIdx

    if (key.upArrow && sel > 0) {
      setSel(v => v - 1)

      return
    }

    if (key.downArrow && sel < count - 1) {
      setSel(v => v + 1)

      return
    }

    if (key.return) {
      if (stage === 'provider') {
        if (!provider) {
          return
        }

        if (provider.authenticated === false) {
          // api_key providers: prompt for key inline
          if (provider.auth_type === 'api_key' && provider.key_env) {
            const fullProviderIdx = providerIndexAfterClearingFilter(providerRows, provider)

            if (fullProviderIdx >= 0) {
              setProviderIdx(fullProviderIdx)
            }

            setStage('key')
            setKeyInput('')
            setKeyError('')
            setFilter('')
          }

          // Other auth types: no-op (warning shown tells them to run hermes model)
          return
        }

        const fullProviderIdx = providerIndexAfterClearingFilter(providerRows, provider)

        if (fullProviderIdx >= 0) {
          setProviderIdx(fullProviderIdx)
        }

        setStage('model')
        setModelIdx(0)
        setFilter('')

        return
      }

      const model = models[modelIdx]

      if (provider && model) {
        onSelect(
          `${model} --provider ${provider.slug}${allowPersistGlobal && persistGlobal ? ' --global' : ` ${TUI_SESSION_MODEL_FLAG}`}`
        )
      } else {
        setStage('provider')
      }

      return
    }

    // Backspace removes the last filter character; Esc (above) clears a
    // non-empty filter before navigating back.
    if (key.backspace || key.delete) {
      setFilter(v => v.slice(0, -1))
      setSel(0)

      return
    }

    // Ctrl+U clears the filter. (Ctrl held → ch is the key name 'u'.)
    if (key.ctrl && ch === 'u') {
      setFilter('')
      setSel(0)

      return
    }

    // Persist-global toggle moved to Ctrl+G so 'g' can be typed into the
    // filter. With Ctrl held, @hermes/ink reports `ch` as the key name ('g'),
    // not the raw control byte (see input-event.ts: input = ctrl ? name : seq).
    if (allowPersistGlobal && key.ctrl && ch === 'g') {
      setPersistGlobal(v => !v)

      return
    }

    // Disconnect (Ctrl+D): only in provider stage, only for authenticated providers.
    if (key.ctrl && ch === 'd' && stage === 'provider' && provider?.authenticated !== false) {
      const fullProviderIdx = providerIndexAfterClearingFilter(providerRows, provider)

      if (fullProviderIdx >= 0) {
        setProviderIdx(fullProviderIdx)
      }

      setStage('disconnect')
      setFilter('')

      return
    }

    // Any other printable single character extends the filter.
    if (ch && !key.ctrl && !key.meta && ch.length === 1 && ch >= ' ') {
      setFilter(v => v + ch)
      setSel(0)
    }
  })

  if (loading) {
    return <Text color={t.color.muted}>loading models…</Text>
  }

  if (err) {
    return (
      <Box flexDirection="column">
        <Text color={t.color.label}>error: {err}</Text>
        <OverlayHint t={t}>Esc/q cancel</OverlayHint>
      </Box>
    )
  }

  if (!providers.length) {
    return (
      <Box flexDirection="column">
        <Text color={t.color.muted}>no providers available</Text>
        <OverlayHint t={t}>Esc/q cancel</OverlayHint>
      </Box>
    )
  }

  // ── Key entry stage ──────────────────────────────────────────────────
  if (stage === 'key' && provider) {
    const masked = keyInput ? '•'.repeat(Math.min(keyInput.length, 40)) : ''

    return (
      <Box flexDirection="column" width={width}>
        <Text bold color={t.color.accent} wrap="truncate-end">
          Configure {provider.name}
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          Paste your API key below (saved to ~/.hermes/.env)
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          {' '}
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          {provider.key_env}:
        </Text>

        <Text color={t.color.accent} wrap="truncate-end">
          {'  '}
          {masked || '(empty)'}
          {keySaving ? '' : '▎'}
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          {' '}
        </Text>

        {keyError ? (
          <Text color={t.color.label} wrap="truncate-end">
            error: {keyError}
          </Text>
        ) : keySaving ? (
          <Text color={t.color.muted} wrap="truncate-end">
            saving…
          </Text>
        ) : (
          <Text color={t.color.muted} wrap="truncate-end">
            {' '}
          </Text>
        )}

        <OverlayHint t={t}>Enter save · Ctrl+U clear · Esc back</OverlayHint>
      </Box>
    )
  }

  // ── Disconnect confirmation stage ─────────────────────────────────────
  if (stage === 'disconnect' && provider) {
    return (
      <Box flexDirection="column" width={width}>
        <Text bold color={t.color.accent} wrap="truncate-end">
          Disconnect {provider.name}?
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          {' '}
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          This removes saved credentials for {provider.name}.
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          You can re-authenticate later by selecting it again.
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          {' '}
        </Text>

        {keySaving ? (
          <Text color={t.color.muted} wrap="truncate-end">
            disconnecting…
          </Text>
        ) : (
          <OverlayHint t={t}>y/Enter confirm · n/Esc cancel</OverlayHint>
        )}
      </Box>
    )
  }

  // ── Provider selection stage ─────────────────────────────────────────
  if (stage === 'provider') {
    const rows = filteredProviderRows.map(({ provider: p, name }) => {
      const authMark = p.authenticated === false ? '○' : p.is_current ? '*' : '●'
      const modelCount = p.total_models ?? p.models?.length ?? 0

      const suffix =
        p.authenticated === false ? (p.auth_type === 'api_key' ? '(no key)' : '(needs setup)') : `${modelCount} models`

      return `${authMark} ${name} · ${suffix}`
    })

    const { items, offset } = windowItems(rows, providerIdx, VISIBLE)
    const noMatches = !!filter.trim() && rows.length === 0

    return (
      <Box flexDirection="column" width={width}>
        <Text bold color={t.color.accent} wrap="truncate-end">
          Select provider (step 1/2)
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          Full model IDs on the next step · Enter to continue
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          Current: {currentModel || '(unknown)'}
        </Text>
        <Text color={filter ? t.color.accent : t.color.muted} wrap="truncate-end">
          {filter ? `filter: ${filter}▎` : 'type to filter · ↑/↓ select'}
        </Text>
        <Text color={t.color.label} wrap="truncate-end">
          {provider?.warning ? `warning: ${provider.warning}` : ' '}
        </Text>
        <Text color={t.color.muted} wrap="truncate-end">
          {offset > 0 ? ` ↑ ${offset} more` : ' '}
        </Text>

        {noMatches ? (
          <Text color={t.color.muted} wrap="truncate-end">
            no providers match
          </Text>
        ) : (
          Array.from({ length: VISIBLE }, (_, i) => {
            const row = items[i]
            const idx = offset + i
            const p = filteredProviderRows[idx]?.provider
            const dimmed = p?.authenticated === false

            return row ? (
              <Text
                bold={providerIdx === idx}
                color={providerIdx === idx ? t.color.accent : dimmed ? t.color.label : t.color.muted}
                inverse={providerIdx === idx}
                key={p?.slug ?? `row-${idx}`}
                wrap="truncate-end"
              >
                {providerIdx === idx ? '▸ ' : '  '}
                {idx + 1}. {row}
              </Text>
            ) : (
              <Text color={t.color.muted} key={`pad-${i}`} wrap="truncate-end">
                {' '}
              </Text>
            )
          })
        )}

        <Text color={t.color.muted} wrap="truncate-end">
          {offset + VISIBLE < rows.length ? ` ↓ ${rows.length - offset - VISIBLE} more` : ' '}
        </Text>

        <Text color={t.color.muted} wrap="truncate-end">
          persist: {allowPersistGlobal ? (persistGlobal ? 'global' : 'session') : 'session'}
          {allowPersistGlobal ? ' · ^g toggle' : ' only'}
        </Text>
        <OverlayHint t={t}>↑/↓ select · Enter choose · ^d disconnect · Esc clear/back · q close</OverlayHint>
      </Box>
    )
  }

  // ── Model selection stage ────────────────────────────────────────────
  const { items, offset } = windowItems(models, modelIdx, VISIBLE)
  const noModelMatches = !!filter.trim() && models.length === 0

  return (
    <Box flexDirection="column" width={width}>
      <Text bold color={t.color.accent} wrap="truncate-end">
        Select model (step 2/2)
      </Text>

      <Text color={t.color.muted} wrap="truncate-end">
        {filteredProviderRows[providerIdx]?.name || '(unknown provider)'} · Esc back
      </Text>
      <Text color={filter ? t.color.accent : t.color.muted} wrap="truncate-end">
        {filter ? `filter: ${filter}▎` : 'type to filter · ↑/↓ select'}
      </Text>
      <Text color={t.color.label} wrap="truncate-end">
        {provider?.warning ? `warning: ${provider.warning}` : ' '}
      </Text>
      <Text color={t.color.muted} wrap="truncate-end">
        {offset > 0 ? ` ↑ ${offset} more` : ' '}
      </Text>

      {Array.from({ length: VISIBLE }, (_, i) => {
        const row = items[i]
        const idx = offset + i

        if (!row) {
          return (!allModels.length || noModelMatches) && i === 0 ? (
            <Text color={t.color.muted} key="empty" wrap="truncate-end">
              {noModelMatches ? 'no models match filter' : 'no models listed for this provider'}
            </Text>
          ) : (
            <Text color={t.color.muted} key={`pad-${i}`} wrap="truncate-end">
              {' '}
            </Text>
          )
        }

        const prefix = modelIdx === idx ? '▸ ' : row === currentModel ? '* ' : '  '

        return (
          <Text
            bold={modelIdx === idx}
            color={modelIdx === idx ? t.color.accent : t.color.muted}
            inverse={modelIdx === idx}
            key={`${provider?.slug ?? 'prov'}:${idx}:${row}`}
            wrap="truncate-end"
          >
            {prefix}
            {idx + 1}. {row}
          </Text>
        )
      })}

      <Text color={t.color.muted} wrap="truncate-end">
        {offset + VISIBLE < models.length ? ` ↓ ${models.length - offset - VISIBLE} more` : ' '}
      </Text>

      <Text color={t.color.muted} wrap="truncate-end">
        persist: {allowPersistGlobal ? (persistGlobal ? 'global' : 'session') : 'session'}
        {allowPersistGlobal ? ' · ^g toggle' : ' only'}
      </Text>
      <OverlayHint t={t}>
        {models.length ? '↑/↓ select · Enter switch · Esc clear/back · q close' : 'Esc back · q close'}
      </OverlayHint>
    </Box>
  )
}

interface ModelPickerProps {
  allowPersistGlobal?: boolean
  gw: GatewayClient
  initialRefresh?: boolean
  onCancel: () => void
  onSelect: (value: string) => void
  sessionId: string | null
  t: Theme
}
