import { existsSync } from 'node:fs'

import { readBoundedText } from '../../lib/bounded-text.js'
import { containedProjectPath } from '../../lib/paths.js'
import { parseStaticJsObject } from '../../lib/static-js-literal.js'
import {
  optionString,
  parseFrontmatter,
  routeSlug,
  scanMarkdownDocs,
  type HumanAdapter,
} from './core.js'

type SidebarDocFilter = {
  readonly ids: ReadonlySet<string>
  readonly autogenDirs: readonly string[]
  readonly enabled: boolean
}

const docusaurusFileSlug = (relPath: string): string => {
  const parts = relPath.split('/')
  const file = parts.at(-1) ?? ''
  const base = file.replace(/\.mdx?$/, '')
  const parent = parts.at(-2)
  if (/^(index|readme)$/i.test(base) || base === parent) return parts.slice(0, -1).join('/')
  return routeSlug(relPath)
}

const docusaurusSlug = (relPath: string, raw: string): string => {
  const slug = parseFrontmatter(raw).slug
  if (!slug) return docusaurusFileSlug(relPath)
  return slug.replace(/^\.\//, '').replace(/^\//, '').replace(/\/$/, '')
}

const docusaurusSidebarId = (relPath: string, raw: string): string => {
  const id = parseFrontmatter(raw).id
  if (!id) return routeSlug(relPath)
  const parts = relPath.split('/').slice(0, -1)
  return [...parts, id].filter(Boolean).join('/')
}

const docusaurusRecordId = (relPath: string, raw: string): string => {
  const frontmatter = parseFrontmatter(raw)
  return frontmatter.package ?? frontmatter.module ?? docusaurusSidebarId(relPath, raw)
}

const readSidebars = (sidebarsFile: string | undefined): SidebarDocFilter => {
  if (!sidebarsFile) return { enabled: false, ids: new Set(), autogenDirs: [] }
  if (!existsSync(sidebarsFile)) return { enabled: false, ids: new Set(), autogenDirs: [] }
  const raw = readBoundedText(sidebarsFile, { used: 0 }, { maxFileBytes: 1_048_576, maxCorpusBytes: 1_048_576 })
  const filter = { ids: new Set<string>(), autogenDirs: [] as string[] }
  const visit = (value: unknown): void => {
    if (typeof value === 'string') {
      filter.ids.add(value)
      return
    }
    if (Array.isArray(value)) {
      for (const item of value) visit(item)
      return
    }
    if (!value || typeof value !== 'object') return
    const item = value as Record<string, unknown>
    if ((item.type === 'doc' || item.type === 'ref') && typeof item.id === 'string') filter.ids.add(item.id)
    if (item.type === 'autogenerated' && typeof item.dirName === 'string') filter.autogenDirs.push(item.dirName)
    if (Array.isArray(item.items)) visit(item.items)
    if (item.link && typeof item.link === 'object') visit(item.link)
    for (const child of Object.values(item)) {
      if (Array.isArray(child)) visit(child)
    }
  }
  visit(parseStaticJsObject(raw))
  return { enabled: true, ...filter }
}

const isIncludedBySidebar = (filter: SidebarDocFilter, id: string): boolean => {
  if (!filter.enabled) return true
  if (filter.ids.has(id)) return true
  return filter.autogenDirs.some((dir) => {
    const prefix = dir === '.' ? '' : dir.replace(/\/$/, '')
    return prefix ? id === prefix || id.startsWith(`${prefix}/`) : true
  })
}

export const docusaurusAdapter: HumanAdapter = {
  plugin: 'docusaurus',
  scan: ({ root, config }) => {
    const docsDir = optionString(config.options, ['docsDir', 'root'])
    if (!docsDir) return []
    const sidebarsFile = optionString(config.options, ['sidebarsFile'])
    const sidebarFilter = readSidebars(sidebarsFile ? containedProjectPath(root, sidebarsFile) : undefined)
    return scanMarkdownDocs(root, docsDir, {
      includeRelPath: (relPath, raw) => isIncludedBySidebar(sidebarFilter, docusaurusSidebarId(relPath, raw)),
      idForDoc: docusaurusRecordId,
      slugForDoc: docusaurusSlug,
      urlPrefix: config.options?.urlPrefix,
    })
  },
}