import {Fragment} from "./fragment"
import {Node} from "./node"
import {Schema, NodeType, MarkType} from "./schema"
import {Mark} from "./mark"
import {DOMNode} from "./dom"

/// A description of a DOM structure. Can be either a string, which is
/// interpreted as a text node, a DOM node, which is interpreted as
/// itself, a `{dom, contentDOM}` object, or an array.
///
/// An array describes a DOM element. The first value in the array
/// should be a string—the name of the DOM element, optionally prefixed
/// by a namespace URL and a space. If the second element is plain
/// object, it is interpreted as a set of attributes for the element.
/// Any elements after that (including the 2nd if it's not an attribute
/// object) are interpreted as children of the DOM elements, and must
/// either be valid `DOMOutputSpec` values, or the number zero.
///
/// The number zero (pronounced “hole”) is used to indicate the place
/// where a node's child nodes should be inserted. If it occurs in an
/// output spec, it should be the only child element in its parent
/// node.
export type DOMOutputSpec = string | DOMNode | {dom: DOMNode, contentDOM?: HTMLElement} | readonly [string, ...any[]]

/// A DOM serializer knows how to convert ProseMirror nodes and
/// marks of various types to DOM nodes.
export class DOMSerializer {
  /// Create a serializer. `nodes` should map node names to functions
  /// that take a node and return a description of the corresponding
  /// DOM. `marks` does the same for mark names, but also gets an
  /// argument that tells it whether the mark's content is block or
  /// inline content (for typical use, it'll always be inline). A mark
  /// serializer may be `null` to indicate that marks of that type
  /// should not be serialized.
  constructor(
    /// The node serialization functions.
    readonly nodes: {[node: string]: (node: Node) => DOMOutputSpec},
    /// The mark serialization functions.
    readonly marks: {[mark: string]: (mark: Mark, inline: boolean) => DOMOutputSpec}
  ) {}

  /// Serialize the content of this fragment to a DOM fragment. When
  /// not in the browser, the `document` option, containing a DOM
  /// document, should be passed so that the serializer can create
  /// nodes.
  serializeFragment(fragment: Fragment, options: {document?: Document} = {}, target?: HTMLElement | DocumentFragment) {
    if (!target) target = doc(options).createDocumentFragment()

    let top = target!, active: [Mark, HTMLElement | DocumentFragment][] = []
    fragment.forEach(node => {
      if (active.length || node.marks.length) {
        let keep = 0, rendered = 0
        while (keep < active.length && rendered < node.marks.length) {
          let next = node.marks[rendered]
          if (!this.marks[next.type.name]) { rendered++; continue }
          if (!next.eq(active[keep][0]) || next.type.spec.spanning === false) break
          keep++; rendered++
        }
        while (keep < active.length) top = active.pop()![1]
        while (rendered < node.marks.length) {
          let add = node.marks[rendered++]
          let markDOM = this.serializeMark(add, node.isInline, options)
          if (markDOM) {
            active.push([add, top])
            top.appendChild(markDOM.dom)
            top = markDOM.contentDOM || markDOM.dom as HTMLElement
          }
        }
      }
      top.appendChild(this.serializeNodeInner(node, options))
    })

    return target
  }

  /// @internal
  serializeNodeInner(node: Node, options: {document?: Document}) {
    let {dom, contentDOM} =
        DOMSerializer.renderSpec(doc(options), this.nodes[node.type.name](node))
    if (contentDOM) {
      if (node.isLeaf)
        throw new RangeError("Content hole not allowed in a leaf node spec")
      this.serializeFragment(node.content, options, contentDOM)
    }
    return dom
  }

  /// Serialize this node to a DOM node. This can be useful when you
  /// need to serialize a part of a document, as opposed to the whole
  /// document. To serialize a whole document, use
  /// [`serializeFragment`](#model.DOMSerializer.serializeFragment) on
  /// its [content](#model.Node.content).
  serializeNode(node: Node, options: {document?: Document} = {}) {
    let dom = this.serializeNodeInner(node, options)
    for (let i = node.marks.length - 1; i >= 0; i--) {
      let wrap = this.serializeMark(node.marks[i], node.isInline, options)
      if (wrap) {
        ;(wrap.contentDOM || wrap.dom).appendChild(dom)
        dom = wrap.dom
      }
    }
    return dom
  }

  /// @internal
  serializeMark(mark: Mark, inline: boolean, options: {document?: Document} = {}) {
    let toDOM = this.marks[mark.type.name]
    return toDOM && DOMSerializer.renderSpec(doc(options), toDOM(mark, inline))
  }

  /// Render an [output spec](#model.DOMOutputSpec) to a DOM node. If
  /// the spec has a hole (zero) in it, `contentDOM` will point at the
  /// node with the hole.
  static renderSpec(doc: Document, structure: DOMOutputSpec, xmlNS: string | null = null): {
    dom: DOMNode,
    contentDOM?: HTMLElement
  } {
    if (typeof structure == "string")
      return {dom: doc.createTextNode(structure)}
    if ((structure as DOMNode).nodeType != null)
      return {dom: structure as DOMNode}
    if ((structure as any).dom && (structure as any).dom.nodeType != null)
      return structure as {dom: DOMNode, contentDOM?: HTMLElement}
    let tagName = (structure as [string])[0], space = tagName.indexOf(" ")
    if (space > 0) {
      xmlNS = tagName.slice(0, space)
      tagName = tagName.slice(space + 1)
    }
    let contentDOM: HTMLElement | undefined
    let dom = (xmlNS ? doc.createElementNS(xmlNS, tagName) : doc.createElement(tagName)) as HTMLElement
    let attrs = (structure as any)[1], start = 1
    if (attrs && typeof attrs == "object" && attrs.nodeType == null && !Array.isArray(attrs)) {
      start = 2
      for (let name in attrs) if (attrs[name] != null) {
        let space = name.indexOf(" ")
        if (space > 0) dom.setAttributeNS(name.slice(0, space), name.slice(space + 1), attrs[name])
        else dom.setAttribute(name, attrs[name])
      }
    }
    for (let i = start; i < (structure as readonly any[]).length; i++) {
      let child = (structure as any)[i] as DOMOutputSpec | 0
      if (child === 0) {
        if (i < (structure as readonly any[]).length - 1 || i > start)
          throw new RangeError("Content hole must be the only child of its parent node")
        return {dom, contentDOM: dom}
      } else {
        let {dom: inner, contentDOM: innerContent} = DOMSerializer.renderSpec(doc, child, xmlNS)
        dom.appendChild(inner)
        if (innerContent) {
          if (contentDOM) throw new RangeError("Multiple content holes")
          contentDOM = innerContent as HTMLElement
        }
      }
    }
    return {dom, contentDOM}
  }

  /// Build a serializer using the [`toDOM`](#model.NodeSpec.toDOM)
  /// properties in a schema's node and mark specs.
  static fromSchema(schema: Schema): DOMSerializer {
    return schema.cached.domSerializer as DOMSerializer ||
      (schema.cached.domSerializer = new DOMSerializer(this.nodesFromSchema(schema), this.marksFromSchema(schema)))
  }

  /// Gather the serializers in a schema's node specs into an object.
  /// This can be useful as a base to build a custom serializer from.
  static nodesFromSchema(schema: Schema) {
    let result = gatherToDOM(schema.nodes)
    if (!result.text) result.text = node => node.text
    return result as {[node: string]: (node: Node) => DOMOutputSpec}
  }

  /// Gather the serializers in a schema's mark specs into an object.
  static marksFromSchema(schema: Schema) {
    return gatherToDOM(schema.marks) as {[mark: string]: (mark: Mark, inline: boolean) => DOMOutputSpec}
  }
}

function gatherToDOM(obj: {[node: string]: NodeType | MarkType}) {
  let result: {[node: string]: (value: any, inline: boolean) => DOMOutputSpec} = {}
  for (let name in obj) {
    let toDOM = obj[name].spec.toDOM
    if (toDOM) result[name] = toDOM
  }
  return result
}

function doc(options: {document?: Document}) {
  return options.document || window.document
}