import { isDynamicRoute } from '../../shared/lib/router/utils'
import type { RouteKind } from '../route-kind'
import type { RouteMatch } from '../route-matches/route-match'
import type { RouteDefinition } from '../route-definitions/route-definition'
import type { RouteMatcherProvider } from '../route-matcher-providers/route-matcher-provider'
import type { RouteMatcher } from '../route-matchers/route-matcher'
import type { MatchOptions, RouteMatcherManager } from './route-matcher-manager'
import { getSortedRoutes } from '../../shared/lib/router/utils'
import { LocaleRouteMatcher } from '../route-matchers/locale-route-matcher'
import { ensureLeadingSlash } from '../../shared/lib/page-path/ensure-leading-slash'
import { DetachedPromise } from '../../lib/detached-promise'

interface RouteMatchers {
  static: ReadonlyArray<RouteMatcher>
  dynamic: ReadonlyArray<RouteMatcher>
  duplicates: Record<string, ReadonlyArray<RouteMatcher>>
}

export class DefaultRouteMatcherManager implements RouteMatcherManager {
  private readonly providers: Array<RouteMatcherProvider> = []
  protected readonly matchers: RouteMatchers = {
    static: [],
    dynamic: [],
    duplicates: {},
  }
  private lastCompilationID = this.compilationID

  /**
   * When this value changes, it indicates that a change has been introduced
   * that requires recompilation.
   */
  private get compilationID() {
    return this.providers.length
  }

  private waitTillReadyPromise?: Promise<void>
  public async waitTillReady(): Promise<void> {
    if (this.waitTillReadyPromise) {
      await this.waitTillReadyPromise
      delete this.waitTillReadyPromise
    }
  }

  private previousMatchers: ReadonlyArray<RouteMatcher> = []
  public async reload() {
    const { promise, resolve, reject } = new DetachedPromise<void>()
    this.waitTillReadyPromise = promise

    // Grab the compilation ID for this run, we'll verify it at the end to
    // ensure that if any routes were added before reloading is finished that
    // we error out.
    const compilationID = this.compilationID

    try {
      // Collect all the matchers from each provider.
      const matchers: Array<RouteMatcher> = []

      // Get all the providers matchers.
      const providersMatchers: ReadonlyArray<ReadonlyArray<RouteMatcher>> =
        await Promise.all(this.providers.map((provider) => provider.matchers()))

      // Use this to detect duplicate pathnames.
      const all = new Map<string, RouteMatcher>()
      const duplicates: Record<string, RouteMatcher[]> = {}
      for (const providerMatchers of providersMatchers) {
        for (const matcher of providerMatchers) {
          // Reset duplicated matches when reloading from pages conflicting state.
          if (matcher.duplicated) delete matcher.duplicated
          // Test to see if the matcher being added is a duplicate.
          const duplicate = all.get(matcher.definition.pathname)
          if (duplicate) {
            // This looks a little weird, but essentially if the pathname
            // already exists in the duplicates map, then we got that array
            // reference. Otherwise, we create a new array with the original
            // duplicate first. Then we push the new matcher into the duplicate
            // array, and reset it to the duplicates object (which may be a
            // no-op if the pathname already existed in the duplicates object).
            // Then we set the array of duplicates on both the original
            // duplicate object and the new one, so we can keep them in sync.
            // If a new duplicate is found, and it matches an existing pathname,
            // the retrieval of the `other` will actually return the array
            // reference used by all other duplicates. This is why ReadonlyArray
            // is so important! Array's are always references!
            const others = duplicates[matcher.definition.pathname] ?? [
              duplicate,
            ]
            others.push(matcher)
            duplicates[matcher.definition.pathname] = others

            // Add duplicated details to each route.
            duplicate.duplicated = others
            matcher.duplicated = others

            // TODO: see if we should error for duplicates in production?
          }

          matchers.push(matcher)

          // Add the matcher's pathname to the set.
          all.set(matcher.definition.pathname, matcher)
        }
      }

      // Update the duplicate matchers. This is used in the development manager
      // to warn about duplicates.
      this.matchers.duplicates = duplicates

      // If the cache is the same as what we just parsed, we can exit now. We
      // can tell by using the `===` which compares object identity, which for
      // the manifest matchers, will return the same matcher each time.
      if (
        this.previousMatchers.length === matchers.length &&
        this.previousMatchers.every(
          (cachedMatcher, index) => cachedMatcher === matchers[index]
        )
      ) {
        return
      }
      this.previousMatchers = matchers

      // For matchers that are for static routes, filter them now.
      this.matchers.static = matchers.filter((matcher) => !matcher.isDynamic)

      // For matchers that are for dynamic routes, filter them and sort them now.
      const dynamic = matchers.filter((matcher) => matcher.isDynamic)

      // As `getSortedRoutes` only takes an array of strings, we need to create
      // a map of the pathnames (used for sorting) and the matchers. When we
      // have locales, there may be multiple matches for the same pathname. To
      // handle this, we keep a map of all the indexes (in `reference`) and
      // merge them in later.

      const reference = new Map<string, number[]>()
      const pathnames = new Array<string>()
      for (let index = 0; index < dynamic.length; index++) {
        // Grab the pathname from the definition.
        const pathname = dynamic[index].definition.pathname

        // Grab the index in the dynamic array, push it into the reference.
        const indexes = reference.get(pathname) ?? []
        indexes.push(index)

        // If this is the first one set it. If it isn't, we don't need to
        // because pushing above on the array will mutate the array already
        // stored there because array's are always a reference!
        if (indexes.length === 1) reference.set(pathname, indexes)
        // Otherwise, continue, we've already added this pathname before.
        else continue

        pathnames.push(pathname)
      }

      // Sort the array of pathnames.
      const sorted = getSortedRoutes(pathnames)

      // For each of the sorted pathnames, iterate over them, grabbing the list
      // of indexes and merging them back into the new `sortedDynamicMatchers`
      // array. The order of the same matching pathname doesn't matter because
      // they will have other matching characteristics (like the locale) that
      // is considered.
      const sortedDynamicMatchers: Array<RouteMatcher> = []
      for (const pathname of sorted) {
        const indexes = reference.get(pathname)
        if (!Array.isArray(indexes)) {
          throw new Error('Invariant: expected to find identity in indexes map')
        }

        const dynamicMatches = indexes.map((index) => dynamic[index])

        sortedDynamicMatchers.push(...dynamicMatches)
      }

      this.matchers.dynamic = sortedDynamicMatchers

      // This means that there was a new matcher pushed while we were waiting
      if (this.compilationID !== compilationID) {
        throw new Error(
          'Invariant: expected compilation to finish before new matchers were added, possible missing await'
        )
      }
    } catch (err) {
      reject(err)
    } finally {
      // The compilation ID matched, so mark the complication as finished.
      this.lastCompilationID = compilationID
      resolve()
    }
  }

  public push(provider: RouteMatcherProvider): void {
    this.providers.push(provider)
  }

  public async test(pathname: string, options: MatchOptions): Promise<boolean> {
    // See if there's a match for the pathname...
    const match = await this.match(pathname, options)

    // This default implementation only needs to check to see if there _was_ a
    // match. The development matcher actually changes it's behavior by not
    // recompiling the routes.
    return match !== null
  }

  public async match(
    pathname: string,
    options: MatchOptions
  ): Promise<RouteMatch<RouteDefinition<RouteKind>> | null> {
    // "Iterate" over the match options. Once we found a single match, exit with
    // it, otherwise return null below. If no match is found, the inner block
    // won't be called.
    for await (const match of this.matchAll(pathname, options)) {
      return match
    }

    return null
  }

  /**
   * This is a point for other managers to override to inject other checking
   * behavior like duplicate route checking on a per-request basis.
   *
   * @param pathname the pathname to validate against
   * @param matcher the matcher to validate/test with
   * @returns the match if found
   */
  protected validate(
    pathname: string,
    matcher: RouteMatcher,
    options: MatchOptions
  ): RouteMatch | null {
    if (matcher instanceof LocaleRouteMatcher) {
      return matcher.match(pathname, options)
    }

    // If the locale was inferred from the default locale, then it will have
    // already added a locale to the pathname. We need to remove it before
    // matching because this matcher is not locale aware.
    if (options.i18n?.inferredFromDefault) {
      return matcher.match(options.i18n.pathname)
    }

    return matcher.match(pathname)
  }

  public async *matchAll(
    pathname: string,
    options: MatchOptions
  ): AsyncGenerator<RouteMatch<RouteDefinition<RouteKind>>, null, undefined> {
    // Guard against the matcher manager from being run before it needs to be
    // recompiled. This was preferred to re-running the compilation here because
    // it should be re-ran only when it changes. If a match is attempted before
    // this is done, it indicates that there is a case where a provider is added
    // before it was recompiled (an error). We also don't want to affect request
    // times.
    if (this.lastCompilationID !== this.compilationID) {
      throw new Error(
        'Invariant: expected routes to have been loaded before match'
      )
    }

    // Ensure that path matching is done with a leading slash.
    pathname = ensureLeadingSlash(pathname)

    // If this pathname doesn't look like a dynamic route, and this pathname is
    // listed in the normalized list of routes, then return it. This ensures
    // that when a route like `/user/[id]` is encountered, it doesn't just match
    // with the list of normalized routes.
    if (!isDynamicRoute(pathname)) {
      for (const matcher of this.matchers.static) {
        const match = this.validate(pathname, matcher, options)
        if (!match) continue

        yield match
      }
    }

    // If we should skip handling dynamic routes, exit now.
    if (options?.skipDynamic) return null

    // Loop over the dynamic matchers, yielding each match.
    for (const matcher of this.matchers.dynamic) {
      const match = this.validate(pathname, matcher, options)
      if (!match) continue

      yield match
    }

    // We tried direct matching against the pathname and against all the dynamic
    // paths, so there was no match.
    return null
  }
}