import localforage from 'localforage'
import { chunk, throttle } from 'lodash'

import { getCssRules } from '../theme_data/css_utils.js'
import { getEngineChecksum, init } from '../theme_data/theme_data_3.service.js'

import { defaultState } from 'src/modules/default_config_state.js'

// On platforms where this is not supported, it will return undefined
// Otherwise it will return an array
const supportsAdoptedStyleSheets = !!document.adoptedStyleSheets

const stylesheets = {}

export const createStyleSheet = (id, priority = 1000) => {
  if (stylesheets[id]) return stylesheets[id]
  const newStyleSheet = {
    rules: [],
    ready: false,
    priority,
    clear() {
      this.rules = []
    },
    addRule(rule) {
      let newRule = rule
      if (!CSS.supports?.('backdrop-filter', 'blur()')) {
        newRule = newRule.replace(/backdrop-filter:[^;]+;/g, '') // Remove backdrop-filter
      }

      // firefox doesn't like invalid selectors
      if (
        !CSS.supports?.('selector(::-webkit-scrollbar)') &&
        newRule.startsWith('::-webkit')
      ) {
        return
      }
      this.rules.push(
        newRule.replace(/var\(--shadowFilter\)[^;]*;/g, ''), // Remove shadowFilter references
      )
    },
  }

  stylesheets[id] = newStyleSheet
  return newStyleSheet
}

export const adoptStyleSheets = throttle(() => {
  if (supportsAdoptedStyleSheets) {
    document.adoptedStyleSheets = Object.values(stylesheets)
      .filter((x) => x.ready)
      .sort((a, b) => a.priority - b.priority)
      .map((sheet) => {
        const css = new CSSStyleSheet()
        sheet.rules.forEach((r) => css.insertRule(r))
        return css
      })
  } else {
    const holder = document.getElementById('custom-styles-holder')

    for (let i = holder.sheet.cssRules.length - 1; i >= 0; --i) {
      holder.sheet.deleteRule(i)
    }

    Object.values(stylesheets)
      .filter((x) => x.ready)
      .sort((a, b) => a.priority - b.priority)
      .forEach((sheet) => {
        sheet.rules.forEach((r) => holder.sheet.insertRule(r))
      })
  }
  // Some older browsers do not support document.adoptedStyleSheets.
  // In this case, we use the <style> elements.
  // Since the <style> elements we need are already in the DOM, there
  // is nothing to do here.
}, 500)

const EAGER_STYLE_ID = 'pleroma-eager-styles'
const LAZY_STYLE_ID = 'pleroma-lazy-styles'

export const generateTheme = (inputRuleset, callbacks, debug) => {
  const {
    onNewRule = () => {
      /* no-op */
    },
    onLazyFinished = () => {
      /* no-op */
    },
    onEagerFinished = () => {
      /* no-op */
    },
  } = callbacks

  const themes3 = init({
    inputRuleset,
    debug,
  })

  getCssRules(themes3.eager, debug).forEach((rule) => {
    // Hacks to support multiple selectors on same component
    onNewRule(rule, false)
  })
  onEagerFinished()

  // Optimization - instead of processing all lazy rules in one go, process them in small chunks
  // so that UI can do other things and be somewhat responsive while less important rules are being
  // processed
  let counter = 0
  const chunks = chunk(themes3.lazy, 200)
  // let t0 = performance.now()
  const processChunk = () => {
    const chunk = chunks[counter]
    Promise.all(chunk.map((x) => x())).then((result) => {
      getCssRules(
        result.filter((x) => x),
        debug,
      ).forEach((rule) => {
        onNewRule(rule, true)
      })
      // const t1 = performance.now()
      // console.debug('Chunk ' + counter + ' took ' + (t1 - t0) + 'ms')
      // t0 = t1
      counter += 1
      if (counter < chunks.length) {
        setTimeout(processChunk, 0)
      } else {
        onLazyFinished()
      }
    })
  }

  return { lazyProcessFunc: processChunk }
}

export const tryLoadCache = async () => {
  console.info('Trying to load compiled theme data from cache')
  const cache = await localforage.getItem('pleromafe-theme-cache')
  if (!cache) return null
  try {
    if (cache.engineChecksum === getEngineChecksum()) {
      const eagerStyles = createStyleSheet(EAGER_STYLE_ID, 10)
      const lazyStyles = createStyleSheet(LAZY_STYLE_ID, 20)

      cache.data[0].forEach((rule) => eagerStyles.addRule(rule))
      cache.data[1].forEach((rule) => lazyStyles.addRule(rule))

      eagerStyles.ready = true
      lazyStyles.ready = true

      console.info(`Loaded theme from cache`)
      return true
    } else {
      console.warn("Engine checksum doesn't match, cache not usable, clearing")
      localStorage.removeItem('pleroma-fe-theme-cache')
    }
  } catch (e) {
    console.error('Failed to load theme cache:', e)
    return false
  }
}

export const applyTheme = (
  input,
  onEagerFinish = () => {
    /* no-op */
  },
  onFinish = () => {
    /* no-op */
  },
  debug,
) => {
  const eagerStyles = createStyleSheet(EAGER_STYLE_ID, 10)
  const lazyStyles = createStyleSheet(LAZY_STYLE_ID, 20)

  eagerStyles.clear()
  lazyStyles.clear()

  const { lazyProcessFunc } = generateTheme(
    input,
    {
      onNewRule(rule, isLazy) {
        if (isLazy) {
          lazyStyles.addRule(rule)
        } else {
          eagerStyles.addRule(rule)
        }
      },
      onEagerFinished() {
        eagerStyles.ready = true
        adoptStyleSheets()
        onEagerFinish()
        console.info(
          'Eager part of theme finished, waiting for lazy part to finish to store cache',
        )
      },
      onLazyFinished() {
        lazyStyles.ready = true
        adoptStyleSheets()
        const cache = {
          engineChecksum: getEngineChecksum(),
          data: [eagerStyles.rules, lazyStyles.rules],
        }
        onFinish(cache)
        localforage.setItem('pleromafe-theme-cache', cache)
        console.info('Theme cache stored')
      },
    },
    debug,
  )

  setTimeout(lazyProcessFunc, 0)
}

const extractStyleConfig = ({
  sidebarColumnWidth,
  contentColumnWidth,
  notifsColumnWidth,
  themeEditorMinWidth,
  emojiReactionsScale,
  emojiSize,
  navbarSize,
  panelHeaderSize,
  textSize,
  forcedRoundness,
}) => {
  const result = {
    sidebarColumnWidth,
    contentColumnWidth,
    notifsColumnWidth,
    themeEditorMinWidth:
      parseInt(themeEditorMinWidth) === 0 ? 'fit-content' : themeEditorMinWidth,
    emojiReactionsScale,
    emojiSize,
    navbarSize,
    panelHeaderSize,
    textSize,
  }

  switch (forcedRoundness) {
    case 'disable':
      break
    case '0':
      result.forcedRoundness = '0'
      break
    case '1':
      result.forcedRoundness = '1px'
      break
    case '2':
      result.forcedRoundness = '0.4rem'
      break
    default:
  }

  return result
}

const defaultStyleConfig = extractStyleConfig(defaultState)

export const applyConfig = (input) => {
  const config = extractStyleConfig(input)

  if (config === defaultStyleConfig) {
    return
  }

  const rules = Object.entries(config)
    .filter(([, v]) => v)
    .map(([k, v]) => `--${k}: ${v}`)
    .join(';')

  const styleSheet = createStyleSheet('theme-holder', 30)

  styleSheet.clear()
  styleSheet.addRule(`:root { ${rules} }`)

  // TODO find a way to make this not apply to theme previews
  if (Object.hasOwn(config, 'forcedRoundness')) {
    styleSheet.addRule(` *:not(.preview-block) {
        --roundness: var(--forcedRoundness) !important;
    }`)
  }
  styleSheet.ready = true
  adoptStyleSheets()
}

export const getResourcesIndex = async (url, parser = JSON.parse) => {
  const cache = 'no-store'
  const customUrl = url.replace(/\.(\w+)$/, '.custom.$1')
  let builtin
  let custom

  const resourceTransform = (resources) => {
    return Object.entries(resources).map(([k, v]) => {
      if (typeof v === 'object') {
        return [k, () => Promise.resolve(v)]
      } else if (typeof v === 'string') {
        return [
          k,
          () =>
            window
              .fetch(v, { cache })
              .then((data) => data.text())
              .then((text) => parser(text))
              .catch((e) => {
                console.error(e)
                return null
              }),
        ]
      } else {
        console.error(`Unknown resource format - ${k} is a ${typeof v}`)
        return [k, null]
      }
    })
  }

  try {
    const builtinData = await window.fetch(url, { cache })
    const builtinResources = await builtinData.json()
    builtin = resourceTransform(builtinResources)
  } catch {
    builtin = []
    console.warn(`Builtin resources at ${url} unavailable`)
  }

  try {
    const customData = await window.fetch(customUrl, { cache })
    const customResources = await customData.json()
    custom = resourceTransform(customResources)
  } catch {
    custom = []
    console.warn(`Custom resources at ${customUrl} unavailable`)
  }

  const total = [...custom, ...builtin]
  if (total.length === 0) {
    return Promise.reject(
      new Error(
        `Resource at ${url} and ${customUrl} completely unavailable. Panicking`,
      ),
    )
  }
  return Promise.resolve(Object.fromEntries(total))
}