import React, {useCallback, useEffect, useMemo, useRef, useState} from 'react'
import {observer} from 'mobx-react-lite'
import {
  ActivityIndicator,
  KeyboardAvoidingView,
  Platform,
  ScrollView,
  StyleSheet,
  TouchableOpacity,
  TouchableWithoutFeedback,
  View,
} from 'react-native'
import {useSafeAreaInsets} from 'react-native-safe-area-context'
import LinearGradient from 'react-native-linear-gradient'
import {FontAwesomeIcon} from '@fortawesome/react-native-fontawesome'
import {RichText} from '@atproto/api'
import {useAnalytics} from 'lib/analytics'
import {UserAutocompleteModel} from 'state/models/discovery/user-autocomplete'
import {ExternalEmbed} from './ExternalEmbed'
import {Text} from '../util/text/Text'
import * as Toast from '../util/Toast'
import {TextInput, TextInputRef} from './text-input/TextInput'
import {CharProgress} from './char-progress/CharProgress'
import {UserAvatar} from '../util/UserAvatar'
import {useStores} from 'state/index'
import * as apilib from 'lib/api/index'
import {ComposerOpts} from 'state/models/ui/shell'
import {s, colors, gradients} from 'lib/styles'
import {sanitizeDisplayName} from 'lib/strings/display-names'
import {cleanError} from 'lib/strings/errors'
import {SelectPhotoBtn} from './photos/SelectPhotoBtn'
import {OpenCameraBtn} from './photos/OpenCameraBtn'
import {usePalette} from 'lib/hooks/usePalette'
import QuoteEmbed from '../util/post-embeds/QuoteEmbed'
import {useExternalLinkFetch} from './useExternalLinkFetch'
import {isDesktopWeb, isAndroid} from 'platform/detection'
import {GalleryModel} from 'state/models/media/gallery'
import {Gallery} from './photos/Gallery'

const MAX_GRAPHEME_LENGTH = 300

type Props = ComposerOpts & {
  onClose: () => void
}

export const ComposePost = observer(function ComposePost({
  replyTo,
  onPost,
  onClose,
  quote: initQuote,
}: Props) {
  const {track} = useAnalytics()
  const pal = usePalette('default')
  const store = useStores()
  const textInput = useRef<TextInputRef>(null)
  const [isProcessing, setIsProcessing] = useState(false)
  const [processingState, setProcessingState] = useState('')
  const [error, setError] = useState('')
  const [richtext, setRichText] = useState(new RichText({text: ''}))
  const graphemeLength = useMemo(() => richtext.graphemeLength, [richtext])
  const [quote, setQuote] = useState<ComposerOpts['quote'] | undefined>(
    initQuote,
  )
  const {extLink, setExtLink} = useExternalLinkFetch({setQuote})
  const [suggestedLinks, setSuggestedLinks] = useState<Set<string>>(new Set())
  const gallery = useMemo(() => new GalleryModel(store), [store])

  const autocompleteView = useMemo<UserAutocompleteModel>(
    () => new UserAutocompleteModel(store),
    [store],
  )

  const insets = useSafeAreaInsets()

  // HACK
  // there's a bug with @mattermost/react-native-paste-input where if the input
  // is focused during unmount, an exception will throw (seems that a blur method isnt implemented)
  // manually blurring before closing gets around that
  // -prf
  const hackfixOnClose = useCallback(() => {
    textInput.current?.blur()
    onClose()
  }, [textInput, onClose])

  // initial setup
  useEffect(() => {
    autocompleteView.setup()
  }, [autocompleteView])

  useEffect(() => {
    // HACK
    // wait a moment before focusing the input to resolve some layout bugs with the keyboard-avoiding-view
    // -prf
    let to: NodeJS.Timeout | undefined
    if (textInput.current) {
      to = setTimeout(() => {
        textInput.current?.focus()
      }, 250)
    }
    return () => {
      if (to) {
        clearTimeout(to)
      }
    }
  }, [])

  const onPressContainer = useCallback(() => {
    textInput.current?.focus()
  }, [textInput])

  const onPressAddLinkCard = useCallback(
    (uri: string) => {
      setExtLink({uri, isLoading: true})
    },
    [setExtLink],
  )

  const onPhotoPasted = useCallback(
    async (uri: string) => {
      track('Composer:PastedPhotos')
      gallery.paste(uri)
    },
    [gallery, track],
  )

  const onPressPublish = useCallback(
    async rt => {
      if (isProcessing || rt.graphemeLength_ > MAX_GRAPHEME_LENGTH) {
        return
      }

      setError('')

      if (rt.text.trim().length === 0 && gallery.isEmpty) {
        setError('Did you want to say anything?')
        return false
      }

      setIsProcessing(true)

      let createdPost
      try {
        createdPost = await apilib.post(store, {
          rawText: rt.text,
          replyTo: replyTo?.uri,
          images: gallery.images,
          quote: quote,
          extLink: extLink,
          onStateChange: setProcessingState,
          knownHandles: autocompleteView.knownHandles,
        })
        track('Create Post', {
          imageCount: gallery.size,
        })
      } catch (e: any) {
        if (extLink) {
          setExtLink({
            ...extLink,
            isLoading: true,
            localThumb: undefined,
          } as apilib.ExternalEmbedDraft)
        }
        setError(cleanError(e.message))
        setIsProcessing(false)
        return
      }
      if (!replyTo) {
        store.me.mainFeed.addPostToTop(createdPost.uri)
      }
      onPost?.()
      hackfixOnClose()
      Toast.show(`Your ${replyTo ? 'reply' : 'post'} has been published`)
    },
    [
      isProcessing,
      setError,
      setIsProcessing,
      replyTo,
      autocompleteView.knownHandles,
      extLink,
      hackfixOnClose,
      onPost,
      quote,
      setExtLink,
      store,
      track,
      gallery,
    ],
  )

  const canPost = graphemeLength <= MAX_GRAPHEME_LENGTH

  const selectTextInputPlaceholder = replyTo ? 'Write your reply' : "What's up?"

  const canSelectImages = gallery.size < 4
  const viewStyles = {
    paddingBottom: isAndroid ? insets.bottom : 0,
    paddingTop: isAndroid ? insets.top : isDesktopWeb ? 0 : 15,
  }

  return (
    <KeyboardAvoidingView
      testID="composePostView"
      behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
      style={styles.outer}>
      <TouchableWithoutFeedback onPressIn={onPressContainer}>
        <View style={[s.flex1, viewStyles]}>
          <View style={styles.topbar}>
            <TouchableOpacity
              testID="composerCancelButton"
              onPress={hackfixOnClose}>
              <Text style={[pal.link, s.f18]}>Cancel</Text>
            </TouchableOpacity>
            <View style={s.flex1} />
            {isProcessing ? (
              <View style={styles.postBtn}>
                <ActivityIndicator />
              </View>
            ) : canPost ? (
              <TouchableOpacity
                testID="composerPublishBtn"
                onPress={() => {
                  onPressPublish(richtext)
                }}>
                <LinearGradient
                  colors={[gradients.blueLight.start, gradients.blueLight.end]}
                  start={{x: 0, y: 0}}
                  end={{x: 1, y: 1}}
                  style={styles.postBtn}>
                  <Text style={[s.white, s.f16, s.bold]}>
                    {replyTo ? 'Reply' : 'Post'}
                  </Text>
                </LinearGradient>
              </TouchableOpacity>
            ) : (
              <View style={[styles.postBtn, pal.btn]}>
                <Text style={[pal.textLight, s.f16, s.bold]}>Post</Text>
              </View>
            )}
          </View>
          {isProcessing ? (
            <View style={[pal.btn, styles.processingLine]}>
              <Text style={pal.text}>{processingState}</Text>
            </View>
          ) : undefined}
          {error !== '' && (
            <View style={styles.errorLine}>
              <View style={styles.errorIcon}>
                <FontAwesomeIcon
                  icon="exclamation"
                  style={{color: colors.red4}}
                  size={10}
                />
              </View>
              <Text style={[s.red4, s.flex1]}>{error}</Text>
            </View>
          )}
          <ScrollView
            style={styles.scrollView}
            keyboardShouldPersistTaps="always">
            {replyTo ? (
              <View style={[pal.border, styles.replyToLayout]}>
                <UserAvatar avatar={replyTo.author.avatar} size={50} />
                <View style={styles.replyToPost}>
                  <Text type="xl-medium" style={[pal.text]}>
                    {sanitizeDisplayName(
                      replyTo.author.displayName || replyTo.author.handle,
                    )}
                  </Text>
                  <Text type="post-text" style={pal.text} numberOfLines={6}>
                    {replyTo.text}
                  </Text>
                </View>
              </View>
            ) : undefined}

            <View style={[pal.border, styles.textInputLayout]}>
              <UserAvatar avatar={store.me.avatar} size={50} />
              <TextInput
                ref={textInput}
                richtext={richtext}
                placeholder={selectTextInputPlaceholder}
                suggestedLinks={suggestedLinks}
                autocompleteView={autocompleteView}
                setRichText={setRichText}
                onPhotoPasted={onPhotoPasted}
                onPressPublish={onPressPublish}
                onSuggestedLinksChanged={setSuggestedLinks}
                onError={setError}
              />
            </View>

            <Gallery gallery={gallery} />
            {gallery.isEmpty && extLink && (
              <ExternalEmbed
                link={extLink}
                onRemove={() => setExtLink(undefined)}
              />
            )}
            {quote ? (
              <View style={s.mt5}>
                <QuoteEmbed quote={quote} />
              </View>
            ) : undefined}
          </ScrollView>
          {!extLink && suggestedLinks.size > 0 ? (
            <View style={s.mb5}>
              {Array.from(suggestedLinks).map(url => (
                <TouchableOpacity
                  key={`suggested-${url}`}
                  testID="addLinkCardBtn"
                  style={[pal.borderDark, styles.addExtLinkBtn]}
                  onPress={() => onPressAddLinkCard(url)}>
                  <Text style={pal.text}>
                    Add link card: <Text style={pal.link}>{url}</Text>
                  </Text>
                </TouchableOpacity>
              ))}
            </View>
          ) : null}
          <View style={[pal.border, styles.bottomBar]}>
            {canSelectImages ? (
              <>
                <SelectPhotoBtn gallery={gallery} />
                <OpenCameraBtn gallery={gallery} />
              </>
            ) : null}
            <View style={s.flex1} />
            <CharProgress count={graphemeLength} />
          </View>
        </View>
      </TouchableWithoutFeedback>
    </KeyboardAvoidingView>
  )
})

const styles = StyleSheet.create({
  outer: {
    flexDirection: 'column',
    flex: 1,
    height: '100%',
  },
  topbar: {
    flexDirection: 'row',
    alignItems: 'center',
    paddingTop: isDesktopWeb ? 10 : undefined,
    paddingBottom: 10,
    paddingHorizontal: 20,
    height: 55,
  },
  postBtn: {
    borderRadius: 20,
    paddingHorizontal: 20,
    paddingVertical: 6,
  },
  processingLine: {
    borderRadius: 6,
    paddingHorizontal: 8,
    paddingVertical: 6,
    marginHorizontal: 15,
    marginBottom: 6,
  },
  errorLine: {
    flexDirection: 'row',
    backgroundColor: colors.red1,
    borderRadius: 6,
    marginHorizontal: 15,
    paddingHorizontal: 8,
    paddingVertical: 6,
    marginVertical: 6,
  },
  errorIcon: {
    borderWidth: 1,
    borderColor: colors.red4,
    color: colors.red4,
    borderRadius: 30,
    width: 16,
    height: 16,
    alignItems: 'center',
    justifyContent: 'center',
    marginRight: 5,
  },
  scrollView: {
    flex: 1,
    paddingHorizontal: 15,
  },
  textInputLayout: {
    flex: isDesktopWeb ? undefined : 1,
    flexDirection: 'row',
    borderTopWidth: 1,
    paddingTop: 16,
  },
  replyToLayout: {
    flexDirection: 'row',
    borderTopWidth: 1,
    paddingTop: 16,
    paddingBottom: 16,
  },
  replyToPost: {
    flex: 1,
    paddingLeft: 13,
    paddingRight: 8,
  },
  addExtLinkBtn: {
    borderWidth: 1,
    borderRadius: 24,
    paddingHorizontal: 16,
    paddingVertical: 12,
    marginHorizontal: 10,
    marginBottom: 4,
  },
  bottomBar: {
    flexDirection: 'row',
    paddingVertical: 10,
    paddingLeft: 15,
    paddingRight: 20,
    alignItems: 'center',
    borderTopWidth: 1,
  },
})