import * as Solid from 'solid-js'
import {
  appendUniqueUserTags,
  escapeHtml,
  getAssetCrossOrigin,
  getScriptPreloadAttrs,
  resolveManifestCssLink,
} from '@tanstack/router-core'
import { useRouter } from './useRouter'
import type {
  AssetCrossOriginConfig,
  RouterManagedTag,
} from '@tanstack/router-core'

/**
 * Build the list of head/link/meta/script tags to render for active matches.
 * Used internally by `HeadContent`.
 */
export const useTags = (assetCrossOrigin?: AssetCrossOriginConfig) => {
  const router = useRouter()
  const nonce = router.options.ssr?.nonce
  const activeMatches = Solid.createMemo(() => router.stores.matches.get())
  const routeMeta = Solid.createMemo(() =>
    activeMatches()
      .map((match) => match.meta)
      .filter((meta) => meta !== undefined),
  )

  const meta: Solid.Accessor<Array<RouterManagedTag>> = Solid.createMemo(() => {
    const resultMeta: Array<RouterManagedTag> = []
    const metaByAttribute: Record<string, true> = {}
    let title: RouterManagedTag | undefined
    const routeMetasArray = routeMeta()
    for (let i = routeMetasArray.length - 1; i >= 0; i--) {
      const metas = routeMetasArray[i]!
      for (let j = metas.length - 1; j >= 0; j--) {
        const m = metas[j]
        if (!m) continue

        if (m.title) {
          if (!title) {
            title = {
              tag: 'title',
              children: m.title,
            }
          }
        } else if ('script:ld+json' in m) {
          // Handle JSON-LD structured data
          // Content is HTML-escaped to prevent XSS when injected via innerHTML
          try {
            const json = JSON.stringify(m['script:ld+json'])
            resultMeta.push({
              tag: 'script',
              attrs: {
                type: 'application/ld+json',
              },
              children: escapeHtml(json),
            })
          } catch {
            // Skip invalid JSON-LD objects
          }
        } else {
          const attribute = m.name ?? m.property
          if (attribute) {
            if (metaByAttribute[attribute]) {
              continue
            } else {
              metaByAttribute[attribute] = true
            }
          }

          resultMeta.push({
            tag: 'meta',
            attrs: {
              ...m,
              nonce,
            },
          })
        }
      }
    }

    if (title) {
      resultMeta.push(title)
    }

    if (router.options.ssr?.nonce) {
      resultMeta.push({
        tag: 'meta',
        attrs: {
          property: 'csp-nonce',
          content: router.options.ssr.nonce,
        },
      })
    }
    resultMeta.reverse()

    return resultMeta
  })

  const links = Solid.createMemo(() => {
    const matches = activeMatches()
    const constructed = matches
      .flatMap((match) => match.links ?? [])
      .filter((link) => link !== undefined)
      .map((link) => ({
        tag: 'link',
        attrs: {
          ...link,
          nonce,
        },
      })) satisfies Array<RouterManagedTag>

    return constructed
  })

  const manifestCssTags = Solid.createMemo(() => {
    const manifest = router.ssr?.manifest
    const tags: Array<RouterManagedTag> = []

    if (!manifest) {
      return tags
    }

    for (const match of activeMatches()) {
      manifest.routes[match.routeId]?.css?.forEach((link) => {
        const resolvedLink = resolveManifestCssLink(link)
        tags.push({
          tag: 'link',
          attrs: {
            rel: 'stylesheet',
            ...resolvedLink,
            crossOrigin:
              getAssetCrossOrigin(assetCrossOrigin, 'stylesheet') ??
              resolvedLink.crossOrigin,
            nonce,
          },
        })
      })
    }

    if (manifest.inlineStyle) {
      tags.push({
        tag: 'style',
        attrs: {
          ...manifest.inlineStyle.attrs,
          nonce,
        },
        children: manifest.inlineStyle.children,
        inlineCss: true,
      })
    }

    return tags
  })

  const preloadLinks = Solid.createMemo(() => {
    const matches = activeMatches()
    const preloadLinks: Array<RouterManagedTag> = []

    matches.forEach((match) =>
      router.ssr?.manifest?.routes[match.routeId]?.preloads
        ?.filter(Boolean)
        .forEach((preload) => {
          preloadLinks.push({
            tag: 'link',
            attrs: {
              ...getScriptPreloadAttrs(
                router.ssr?.manifest,
                preload,
                assetCrossOrigin,
              ),
              nonce,
            },
          })
        }),
    )

    return preloadLinks
  })

  const styles = Solid.createMemo(() => {
    return activeMatches()
      .flatMap((match) => match.styles ?? [])
      .filter((style) => style !== undefined)
      .map(({ children, ...style }) => ({
        tag: 'style',
        attrs: {
          ...style,
          nonce,
        },
        children: children as string | undefined,
      })) satisfies Array<RouterManagedTag>
  })

  const headScripts = Solid.createMemo(() => {
    return activeMatches()
      .flatMap((match) => match.headScripts ?? [])
      .filter((script) => script !== undefined)
      .map(({ children, ...script }) => ({
        tag: 'script',
        attrs: {
          ...script,
          nonce,
        },
        children: children as string | undefined,
      })) satisfies Array<RouterManagedTag>
  })

  return Solid.createMemo((prev: Array<RouterManagedTag> | undefined) => {
    const next: Array<RouterManagedTag> = []
    appendUniqueUserTags(next, meta())
    next.push(...preloadLinks())
    appendUniqueUserTags(next, links())
    next.push(...manifestCssTags())
    appendUniqueUserTags(next, styles())
    appendUniqueUserTags(next, headScripts())

    if (prev === undefined) {
      return next
    }
    return replaceEqualTags(prev, next)
  })
}

function replaceEqualTags(
  prev: Array<RouterManagedTag>,
  next: Array<RouterManagedTag>,
) {
  const prevByKey = new Map<string, RouterManagedTag>()
  for (const tag of prev) {
    prevByKey.set(JSON.stringify(tag), tag)
  }

  let isEqual = prev.length === next.length
  const result = next.map((tag, index) => {
    const existing = prevByKey.get(JSON.stringify(tag))
    if (existing) {
      if (existing !== prev[index]) {
        isEqual = false
      }
      return existing
    }

    isEqual = false
    return tag
  })

  return isEqual ? prev : result
}