/**
 * @typedef {import('unist').Node} Node
 * @typedef {import('unist').Parent} Parent
 * @typedef {import('unist-util-is').Test} Test
 */

/**
 * @typedef {boolean | 'skip'} Action
 *   Union of the action types.
 *
 * @typedef {number} Index
 *   Move to the sibling at `index` next (after node itself is completely
 *   traversed).
 *
 *   Useful if mutating the tree, such as removing the node the visitor is
 *   currently on, or any of its previous siblings.
 *   Results less than 0 or greater than or equal to `children.length` stop
 *   traversing the parent.
 *
 * @typedef {[(Action | null | undefined | void)?, (Index | null | undefined)?]} ActionTuple
 *   List with one or two values, the first an action, the second an index.
 *
 * @typedef {Action | ActionTuple | Index | null | undefined | void} VisitorResult
 *   Any value that can be returned from a visitor.
 */

/**
 * @template {Node} [Visited=Node]
 *   Visited node type.
 * @template {Parent} [Ancestor=Parent]
 *   Ancestor type.
 * @callback Visitor
 *   Handle a node (matching `test`, if given).
 *
 *   Visitors are free to transform `node`.
 *   They can also transform the parent of node (the last of `ancestors`).
 *
 *   Replacing `node` itself, if `SKIP` is not returned, still causes its
 *   descendants to be walked (which is a bug).
 *
 *   When adding or removing previous siblings of `node` (or next siblings, in
 *   case of reverse), the `Visitor` should return a new `Index` to specify the
 *   sibling to traverse after `node` is traversed.
 *   Adding or removing next siblings of `node` (or previous siblings, in case
 *   of reverse) is handled as expected without needing to return a new `Index`.
 *
 *   Removing the children property of an ancestor still results in them being
 *   traversed.
 * @param {Visited} node
 *   Found node.
 * @param {Array<Ancestor>} ancestors
 *   Ancestors of `node`.
 * @returns {VisitorResult}
 *   What to do next.
 *
 *   An `Index` is treated as a tuple of `[CONTINUE, Index]`.
 *   An `Action` is treated as a tuple of `[Action]`.
 *
 *   Passing a tuple back only makes sense if the `Action` is `SKIP`.
 *   When the `Action` is `EXIT`, that action can be returned.
 *   When the `Action` is `CONTINUE`, `Index` can be returned.
 */

/**
 * @template {Node} [Tree=Node]
 *   Tree type.
 * @template {Test} [Check=string]
 *   Test type.
 * @typedef {Visitor<import('./complex-types.js').Matches<import('./complex-types.js').InclusiveDescendant<Tree>, Check>, Extract<import('./complex-types.js').InclusiveDescendant<Tree>, Parent>>} BuildVisitor
 *   Build a typed `Visitor` function from a tree and a test.
 *
 *   It will infer which values are passed as `node` and which as `parents`.
 */

import {convert} from 'unist-util-is'
import {color} from './color.js'

/**
 * Continue traversing as normal.
 */
export const CONTINUE = true

/**
 * Stop traversing immediately.
 */
export const EXIT = false

/**
 * Do not traverse this node’s children.
 */
export const SKIP = 'skip'

/**
 * Visit nodes, with ancestral information.
 *
 * This algorithm performs *depth-first* *tree traversal* in *preorder*
 * (**NLR**) or if `reverse` is given, in *reverse preorder* (**NRL**).
 *
 * You can choose for which nodes `visitor` is called by passing a `test`.
 * For complex tests, you should test yourself in `visitor`, as it will be
 * faster and will have improved type information.
 *
 * Walking the tree is an intensive task.
 * Make use of the return values of the visitor when possible.
 * Instead of walking a tree multiple times, walk it once, use `unist-util-is`
 * to check if a node matches, and then perform different operations.
 *
 * You can change the tree.
 * See `Visitor` for more info.
 *
 * @param tree
 *   Tree to traverse.
 * @param test
 *   `unist-util-is`-compatible test
 * @param visitor
 *   Handle each node.
 * @param reverse
 *   Traverse in reverse preorder (NRL) instead of the default preorder (NLR).
 * @returns
 *   Nothing.
 */
export const visitParents =
  /**
   * @type {(
   *   (<Tree extends Node, Check extends Test>(tree: Tree, test: Check, visitor: BuildVisitor<Tree, Check>, reverse?: boolean | null | undefined) => void) &
   *   (<Tree extends Node>(tree: Tree, visitor: BuildVisitor<Tree>, reverse?: boolean | null | undefined) => void)
   * )}
   */
  (
    /**
     * @param {Node} tree
     * @param {Test} test
     * @param {Visitor<Node>} visitor
     * @param {boolean | null | undefined} [reverse]
     * @returns {void}
     */
    function (tree, test, visitor, reverse) {
      if (typeof test === 'function' && typeof visitor !== 'function') {
        reverse = visitor
        // @ts-expect-error no visitor given, so `visitor` is test.
        visitor = test
        test = null
      }

      const is = convert(test)
      const step = reverse ? -1 : 1

      factory(tree, undefined, [])()

      /**
       * @param {Node} node
       * @param {number | undefined} index
       * @param {Array<Parent>} parents
       */
      function factory(node, index, parents) {
        /** @type {Record<string, unknown>} */
        // @ts-expect-error: hush
        const value = node && typeof node === 'object' ? node : {}

        if (typeof value.type === 'string') {
          const name =
            // `hast`
            typeof value.tagName === 'string'
              ? value.tagName
              : // `xast`
              typeof value.name === 'string'
              ? value.name
              : undefined

          Object.defineProperty(visit, 'name', {
            value:
              'node (' + color(node.type + (name ? '<' + name + '>' : '')) + ')'
          })
        }

        return visit

        function visit() {
          /** @type {ActionTuple} */
          let result = []
          /** @type {ActionTuple} */
          let subresult
          /** @type {number} */
          let offset
          /** @type {Array<Parent>} */
          let grandparents

          if (!test || is(node, index, parents[parents.length - 1] || null)) {
            result = toResult(visitor(node, parents))

            if (result[0] === EXIT) {
              return result
            }
          }

          // @ts-expect-error looks like a parent.
          if (node.children && result[0] !== SKIP) {
            // @ts-expect-error looks like a parent.
            offset = (reverse ? node.children.length : -1) + step
            // @ts-expect-error looks like a parent.
            grandparents = parents.concat(node)

            // @ts-expect-error looks like a parent.
            while (offset > -1 && offset < node.children.length) {
              // @ts-expect-error looks like a parent.
              subresult = factory(node.children[offset], offset, grandparents)()

              if (subresult[0] === EXIT) {
                return subresult
              }

              offset =
                typeof subresult[1] === 'number' ? subresult[1] : offset + step
            }
          }

          return result
        }
      }
    }
  )

/**
 * Turn a return value into a clean result.
 *
 * @param {VisitorResult} value
 *   Valid return values from visitors.
 * @returns {ActionTuple}
 *   Clean result.
 */
function toResult(value) {
  if (Array.isArray(value)) {
    return value
  }

  if (typeof value === 'number') {
    return [CONTINUE, value]
  }

  return [value]
}