import { SchemaVersion, type Section } from '@defra/forms-model'

import { PaymentField } from '~/src/server/plugins/engine/components/PaymentField.js'
import { type PaymentState } from '~/src/server/plugins/engine/components/PaymentField.types.js'
import {
  getAnswer,
  type Field
} from '~/src/server/plugins/engine/components/helpers/components.js'
import {
  type BackLink,
  type ComponentViewModel
} from '~/src/server/plugins/engine/components/types.js'
import {
  evaluateTemplate,
  getError,
  getPageHref
} from '~/src/server/plugins/engine/helpers.js'
import {
  type Detail,
  type DetailItem,
  type DetailItemField,
  type DetailItemRepeat
} from '~/src/server/plugins/engine/models/types.js'
import { RepeatPageController } from '~/src/server/plugins/engine/pageControllers/RepeatPageController.js'
import { type PageControllerClass } from '~/src/server/plugins/engine/pageControllers/helpers/pages.js'
import { validationOptions as opts } from '~/src/server/plugins/engine/pageControllers/validationOptions.js'
import {
  type CheckAnswers,
  type FormContext,
  type FormContextRequest,
  type FormState,
  type FormSubmissionError,
  type SummaryListAction,
  type SummaryListRow
} from '~/src/server/plugins/engine/types.js'

export class SummaryViewModel {
  /**
   * Responsible for parsing state values to the govuk-frontend summary list template
   */

  page: PageControllerClass
  pageTitle: string
  declaration?: string
  details: Detail[]
  checkAnswers: CheckAnswers[]
  context: FormContext
  name: string | undefined
  backLink?: BackLink
  feedbackLink?: string
  phaseTag?: string
  errors?: FormSubmissionError[]
  serviceUrl: string
  hasMissingNotificationEmail?: boolean
  components?: ComponentViewModel[]
  allowSaveAndExit = false
  paymentState?: PaymentState
  paymentDetails?: CheckAnswers

  constructor(
    request: FormContextRequest,
    page: PageControllerClass,
    context: FormContext
  ) {
    const { model } = page
    const { basePath, def, sections } = model
    const { isForceAccess } = context

    this.page = page
    this.pageTitle = page.title
    if (def.schema === SchemaVersion.V2 && !page.title) {
      this.pageTitle = 'Check your answers before sending your form'
    }

    this.serviceUrl = `/${basePath}`
    this.name = def.name
    this.declaration = def.declaration
    this.context = context

    const result = model
      .makeFilteredSchema(this.context.relevantPages)
      .validate(this.context.relevantState, { ...opts, stripUnknown: true })

    // Format errors
    this.errors = result.error?.details.map(getError)
    this.details = this.summaryDetails(request, sections)

    // Format check answers
    this.checkAnswers = this.details.map((detail): CheckAnswers => {
      const { title } = detail

      const rows = detail.items.map((item): SummaryListRow => {
        const items: SummaryListAction[] = []

        // Remove summary list actions from previews
        if (!isForceAccess) {
          items.push({
            href: item.href,
            text: 'Change',
            classes: 'govuk-link--no-visited-state',
            visuallyHiddenText: item.label
          })
        }

        return {
          key: {
            text: evaluateTemplate(item.title, context)
          },
          value: {
            classes: 'app-prose-scope',
            html: item.value || 'Not provided'
          },
          actions: {
            items
          }
        }
      })

      return {
        title: title ? { text: title } : undefined,
        summaryList: { rows }
      }
    })
  }

  private summaryDetails(request: FormContextRequest, sections: Section[]) {
    const { context, errors } = this
    const { relevantPages, state } = context

    const details: Detail[] = []

    ;[...sections, undefined].forEach((section) => {
      const items: DetailItem[] = []

      const sectionPages = relevantPages.filter(
        (page) => page.section === section
      )

      sectionPages.forEach((page) => {
        const { collection, path } = page

        if (page instanceof RepeatPageController) {
          items.push(
            ItemRepeat(page, state, {
              path: page.getSummaryPath(request),
              errors
            })
          )
        } else {
          for (const field of collection.fields) {
            // PaymentField is rendered in its own section, skip it here
            if (field instanceof PaymentField) {
              continue
            }
            items.push(ItemField(page, state, field, { path, errors }))
          }
        }
      })

      if (items.length) {
        details.push({
          name: section?.name,
          title: section?.title,
          items
        })
      }
    })

    return details
  }
}

/**
 * Creates a repeater detail item
 * @see {@link DetailItemField}
 */
function ItemRepeat(
  page: RepeatPageController,
  state: FormState,
  options: {
    path: string
    errors?: FormSubmissionError[]
  }
): DetailItemRepeat {
  const { collection, repeat } = page
  const { name, title } = repeat.options

  const values = page.getListFromState(state)
  const unit = values.length === 1 ? 'answer' : 'answers'

  return {
    name,
    label: title,
    title,
    value: values.length ? `You have added ${values.length} ${unit}` : '',
    href: getPageHref(page, options.path, {
      returnUrl: getPageHref(page, page.getSummaryPath())
    }),
    state,
    page,

    // Repeater field detail items
    subItems: values.map((repeatState) =>
      collection.fields.map((field) =>
        ItemField(page, repeatState, field, options)
      )
    )
  }
}

/**
 * Creates a form field detail item
 * @see {@link DetailItemField}
 */
export function ItemField(
  page: PageControllerClass,
  state: FormState,
  field: Field,
  options: {
    path: string
    errors?: FormSubmissionError[]
  }
): DetailItemField {
  return {
    name: field.name,
    label: field.title,
    title:
      field.options.required === false
        ? `${field.label} (optional)`
        : field.label,
    error: field.getFirstError(options.errors),
    value: getAnswer(field, state),
    href: getPageHref(page, options.path, {
      returnUrl: getPageHref(page, page.getSummaryPath())
    }),
    state,
    page,
    field
  }
}