import { computed, isReadonly, reactive, shallowRef } from 'vue'
import type { Ref } from 'vue'
import type { RouteLocation, Router, RouterScrollBehavior } from '#vue-router'
import {
  START_LOCATION,
  createMemoryHistory,
  createRouter,
  createWebHashHistory,
  createWebHistory
} from '#vue-router'
import { createError } from 'h3'
import { withoutBase } from 'ufo'

import type { PageMeta, Plugin, RouteMiddleware } from '../../../app/index'
import { defineNuxtPlugin, useRuntimeConfig } from '#app/nuxt'
import { clearError, showError, useError } from '#app/composables/error'
import { useState } from '#app/composables/state'
import { navigateTo } from '#app/composables/router'

// @ts-expect-error virtual file
import _routes from '#build/routes'
// @ts-expect-error virtual file
import routerOptions from '#build/router.options'
// @ts-expect-error virtual file
import { globalMiddleware, namedMiddleware } from '#build/middleware'

// https://github.com/vuejs/router/blob/4a0cc8b9c1e642cdf47cc007fa5bbebde70afc66/packages/router/src/history/html5.ts#L37
function createCurrentLocation (
  base: string,
  location: Location
): string {
  const { pathname, search, hash } = location
  // allows hash bases like #, /#, #/, #!, #!/, /#!/, or even /folder#end
  const hashPos = base.indexOf('#')
  if (hashPos > -1) {
    const slicePos = hash.includes(base.slice(hashPos))
      ? base.slice(hashPos).length
      : 1
    let pathFromHash = hash.slice(slicePos)
    // prepend the starting slash to hash so the url starts with /#
    if (pathFromHash[0] !== '/') { pathFromHash = '/' + pathFromHash }
    return withoutBase(pathFromHash, '')
  }
  const path = withoutBase(pathname, base)
  return path + search + hash
}

const plugin: Plugin<{ router: Router }> = defineNuxtPlugin({
  name: 'nuxt:router',
  enforce: 'pre',
  async setup (nuxtApp) {
    let routerBase = useRuntimeConfig().app.baseURL
    if (routerOptions.hashMode && !routerBase.includes('#')) {
      // allow the user to provide a `#` in the middle: `/base/#/app`
      routerBase += '#'
    }

    const history = routerOptions.history?.(routerBase) ?? (process.client
      ? (routerOptions.hashMode ? createWebHashHistory(routerBase) : createWebHistory(routerBase))
      : createMemoryHistory(routerBase)
    )

    const routes = routerOptions.routes?.(_routes) ?? _routes

    let startPosition: Parameters<RouterScrollBehavior>[2] | null
    const initialURL = process.server ? nuxtApp.ssrContext!.url : createCurrentLocation(routerBase, window.location)
    const router = createRouter({
      ...routerOptions,
      scrollBehavior: (to, from, savedPosition) => {
        if (from === START_LOCATION) {
          startPosition = savedPosition
          return
        }
        // reset scroll behavior to initial value
        router.options.scrollBehavior = routerOptions.scrollBehavior
        return routerOptions.scrollBehavior?.(to, START_LOCATION, startPosition || savedPosition)
      },
      history,
      routes
    })
    nuxtApp.vueApp.use(router)

    const previousRoute = shallowRef(router.currentRoute.value)
    router.afterEach((_to, from) => {
      previousRoute.value = from
    })

    Object.defineProperty(nuxtApp.vueApp.config.globalProperties, 'previousRoute', {
      get: () => previousRoute.value
    })

    // Allows suspending the route object until page navigation completes
    const _route = shallowRef(router.resolve(initialURL) as RouteLocation)
    const syncCurrentRoute = () => { _route.value = router.currentRoute.value }
    nuxtApp.hook('page:finish', syncCurrentRoute)
    router.afterEach((to, from) => {
      // We won't trigger suspense if the component is reused between routes
      // so we need to update the route manually
      if (to.matched[0]?.components?.default === from.matched[0]?.components?.default) {
        syncCurrentRoute()
      }
    })

    // https://github.com/vuejs/router/blob/main/packages/router/src/router.ts#L1225-L1233
    const route = {} as RouteLocation
    for (const key in _route.value) {
      (route as any)[key] = computed(() => _route.value[key as keyof RouteLocation])
    }

    nuxtApp._route = reactive(route)

    nuxtApp._middleware = nuxtApp._middleware || {
      global: [],
      named: {}
    }

    const error = useError()

    try {
      if (process.server) {
        await router.push(initialURL)
      }

      await router.isReady()
    } catch (error: any) {
      // We'll catch 404s here
      await nuxtApp.runWithContext(() => showError(error))
    }

    const initialLayout = useState('_layout')
    router.beforeEach(async (to, from) => {
      to.meta = reactive(to.meta)
      if (nuxtApp.isHydrating && initialLayout.value && !isReadonly(to.meta.layout)) {
        to.meta.layout = initialLayout.value as Exclude<PageMeta['layout'], Ref | false>
      }
      nuxtApp._processingMiddleware = true

      type MiddlewareDef = string | RouteMiddleware
      const middlewareEntries = new Set<MiddlewareDef>([...globalMiddleware, ...nuxtApp._middleware.global])
      for (const component of to.matched) {
        const componentMiddleware = component.meta.middleware as MiddlewareDef | MiddlewareDef[]
        if (!componentMiddleware) { continue }
        if (Array.isArray(componentMiddleware)) {
          for (const entry of componentMiddleware) {
            middlewareEntries.add(entry)
          }
        } else {
          middlewareEntries.add(componentMiddleware)
        }
      }

      for (const entry of middlewareEntries) {
        const middleware = typeof entry === 'string' ? nuxtApp._middleware.named[entry] || await namedMiddleware[entry]?.().then((r: any) => r.default || r) : entry

        if (!middleware) {
          if (process.dev) {
            throw new Error(`Unknown route middleware: '${entry}'. Valid middleware: ${Object.keys(namedMiddleware).map(mw => `'${mw}'`).join(', ')}.`)
          }
          throw new Error(`Unknown route middleware: '${entry}'.`)
        }

        const result = await nuxtApp.runWithContext(() => middleware(to, from))
        if (process.server || (!nuxtApp.payload.serverRendered && nuxtApp.isHydrating)) {
          if (result === false || result instanceof Error) {
            const error = result || createError({
              statusCode: 404,
              statusMessage: `Page Not Found: ${initialURL}`
            })
            await nuxtApp.runWithContext(() => showError(error))
            return false
          }
        }
        if (result || result === false) { return result }
      }
    })

    router.onError(() => { delete nuxtApp._processingMiddleware })

    router.afterEach(async (to, _from, failure) => {
      delete nuxtApp._processingMiddleware

      if (process.client && !nuxtApp.isHydrating && error.value) {
        // Clear any existing errors
        await nuxtApp.runWithContext(clearError)
      }
      if (process.server && failure?.type === 4 /* ErrorTypes.NAVIGATION_ABORTED */) {
        return
      }
      if (to.matched.length === 0) {
        await nuxtApp.runWithContext(() => showError(createError({
          statusCode: 404,
          fatal: false,
          statusMessage: `Page not found: ${to.fullPath}`
        })))
      } else if (process.server && to.redirectedFrom) {
        await nuxtApp.runWithContext(() => navigateTo(to.fullPath || '/'))
      }
    })

    nuxtApp.hooks.hookOnce('app:created', async () => {
      try {
        await router.replace({
          ...router.resolve(initialURL),
          name: undefined, // #4920, #4982
          force: true
        })
        // reset scroll behavior to initial value
        router.options.scrollBehavior = routerOptions.scrollBehavior
      } catch (error: any) {
        // We'll catch middleware errors or deliberate exceptions here
        await nuxtApp.runWithContext(() => showError(error))
      }
    })

    return { provide: { router } }
  }
})

export default plugin