/**
 * @import {
 *   CompileContext,
 *   Extension as FromMarkdownExtension,
 *   Handle as FromMarkdownHandle
 * } from 'mdast-util-from-markdown'
 * @import {ToMarkdownOptions} from 'mdast-util-gfm-footnote'
 * @import {
 *   Handle as ToMarkdownHandle,
 *   Map,
 *   Options as ToMarkdownExtension
 * } from 'mdast-util-to-markdown'
 * @import {FootnoteDefinition, FootnoteReference} from 'mdast'
 */

import {ok as assert} from 'devlop'
import {normalizeIdentifier} from 'micromark-util-normalize-identifier'

footnoteReference.peek = footnoteReferencePeek

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function enterFootnoteCallString() {
  this.buffer()
}

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function enterFootnoteCall(token) {
  this.enter({type: 'footnoteReference', identifier: '', label: ''}, token)
}

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function enterFootnoteDefinitionLabelString() {
  this.buffer()
}

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function enterFootnoteDefinition(token) {
  this.enter(
    {type: 'footnoteDefinition', identifier: '', label: '', children: []},
    token
  )
}

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function exitFootnoteCallString(token) {
  const label = this.resume()
  const node = this.stack[this.stack.length - 1]
  assert(node.type === 'footnoteReference')
  node.identifier = normalizeIdentifier(
    this.sliceSerialize(token)
  ).toLowerCase()
  node.label = label
}

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function exitFootnoteCall(token) {
  this.exit(token)
}

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function exitFootnoteDefinitionLabelString(token) {
  const label = this.resume()
  const node = this.stack[this.stack.length - 1]
  assert(node.type === 'footnoteDefinition')
  node.identifier = normalizeIdentifier(
    this.sliceSerialize(token)
  ).toLowerCase()
  node.label = label
}

/**
 * @this {CompileContext}
 * @type {FromMarkdownHandle}
 */
function exitFootnoteDefinition(token) {
  this.exit(token)
}

/** @type {ToMarkdownHandle} */
function footnoteReferencePeek() {
  return '['
}

/**
 * @type {ToMarkdownHandle}
 * @param {FootnoteReference} node
 */
function footnoteReference(node, _, state, info) {
  const tracker = state.createTracker(info)
  let value = tracker.move('[^')
  const exit = state.enter('footnoteReference')
  const subexit = state.enter('reference')
  value += tracker.move(
    state.safe(state.associationId(node), {after: ']', before: value})
  )
  subexit()
  exit()
  value += tracker.move(']')
  return value
}

/**
 * Create an extension for `mdast-util-from-markdown` to enable GFM footnotes
 * in markdown.
 *
 * @returns {FromMarkdownExtension}
 *   Extension for `mdast-util-from-markdown`.
 */
export function gfmFootnoteFromMarkdown() {
  return {
    enter: {
      gfmFootnoteCallString: enterFootnoteCallString,
      gfmFootnoteCall: enterFootnoteCall,
      gfmFootnoteDefinitionLabelString: enterFootnoteDefinitionLabelString,
      gfmFootnoteDefinition: enterFootnoteDefinition
    },
    exit: {
      gfmFootnoteCallString: exitFootnoteCallString,
      gfmFootnoteCall: exitFootnoteCall,
      gfmFootnoteDefinitionLabelString: exitFootnoteDefinitionLabelString,
      gfmFootnoteDefinition: exitFootnoteDefinition
    }
  }
}

/**
 * Create an extension for `mdast-util-to-markdown` to enable GFM footnotes
 * in markdown.
 *
 * @param {ToMarkdownOptions | null | undefined} [options]
 *   Configuration (optional).
 * @returns {ToMarkdownExtension}
 *   Extension for `mdast-util-to-markdown`.
 */
export function gfmFootnoteToMarkdown(options) {
  // To do: next major: change default.
  let firstLineBlank = false

  if (options && options.firstLineBlank) {
    firstLineBlank = true
  }

  return {
    handlers: {footnoteDefinition, footnoteReference},
    // This is on by default already.
    unsafe: [{character: '[', inConstruct: ['label', 'phrasing', 'reference']}]
  }

  /**
   * @type {ToMarkdownHandle}
   * @param {FootnoteDefinition} node
   */
  function footnoteDefinition(node, _, state, info) {
    const tracker = state.createTracker(info)
    let value = tracker.move('[^')
    const exit = state.enter('footnoteDefinition')
    const subexit = state.enter('label')
    value += tracker.move(
      state.safe(state.associationId(node), {before: value, after: ']'})
    )
    subexit()

    value += tracker.move(']:')

    if (node.children && node.children.length > 0) {
      tracker.shift(4)

      value += tracker.move(
        (firstLineBlank ? '\n' : ' ') +
          state.indentLines(
            state.containerFlow(node, tracker.current()),
            firstLineBlank ? mapAll : mapExceptFirst
          )
      )
    }

    exit()

    return value
  }
}

/** @type {Map} */
function mapExceptFirst(line, index, blank) {
  return index === 0 ? line : mapAll(line, index, blank)
}

/** @type {Map} */
function mapAll(line, index, blank) {
  return (blank ? '' : '    ') + line
}