/* gmi.js is licensed under CC0 */
class Gemini {
  static line(line) {
    let dom = Gemini.render(line).dom
    return {
      get dom() { return dom },
      get type() { return this.dom.nodeName },
      set type(type) { dom = Gemini.render({dom, type, content: Gemini.contentFrom(dom)}).dom },
      get content() { return Gemini.contentFrom(dom) },
      set content(content) { dom = Gemini.render({dom, type: dom.nodeName, content}) },
      get editable() { return this.dom.contentEditable === "true" },
      set editable(value) { Gemini.render({dom: this.dom, type: this.type, content: this.content, editable: value}) },
      delete() { return this.dom.remove() },
      get gmi() { 
        const syntax = Gemini.syntax[this.type]
        const content = Gemini.contentFrom(this.dom).replace(/\n?$/, "")
        switch (this.type) {
          case Gemini.type.PREFORMATTED:
            return `${syntax}\n${content}\n${syntax}`
            break
          default:
            return content.split("\n").map(line => 
              `${syntax !== "" ? syntax + " " : ""}${line}`
            ).join("\n")
        }
      },
      get before() { return Gemini.line(this.dom.previousElementSibling) },
      set before(line) { this.before.dom.after(line.dom) },
      get after() { return Gemini.line(this.dom.nextElementSibling) },
      set after(line) { this.after.dom.before(line.dom) },
    }
  }
  static render(line) {
    if (line.dom && line.dom.nodeName !== line.type) {
      const replacement = document.createElement(line.type)
      line.dom.replaceWith(replacement)
      line.dom = replacement
    } else if (line.nodeName) {
      line = {
        dom: line, 
        type: line.nodeName, 
        content: Gemini.contentFrom(line),
        editable: line.contentEditable
      }
    } else {
      line.dom = line.dom || document.createElement(line.type || Gemini.type.TEXT)
    }
    line.dom.contentEditable = line.editable || "inherit"
    switch (line.type) {
      case Gemini.type.LINK:
        const {href, content} = Gemini.PARSE_LINK.exec(line.content).groups
        line.dom.innerHTML = line.editable && href !== content ? `${href} ${content}` :  content 
        line.dom.href = href 
        break
      case Gemini.type.LIST: 
        line.dom.innerHTML = line.content.split("\n").map(content => 
          content.length > 0 ? `<li>${content}</li>` : ""
        ).join("\n")
        break
      case Gemini.type.QUOTE: 
        line.dom.innerHTML = line.content.split("\n").map(content => 
          `<div>${content}</div>`
        ).join("\n")
        break
      case Gemini.type.PREFORMATTED:
        line.dom.textContent = line.content
        break
      default:
        line.dom.innerHTML = line.content.replace(/\n+/g, "<br>") 
    }
    return line 
  }
  static contentFrom(dom) {
    switch (dom.nodeName) {
      case Gemini.type.QUOTE:
        return Array.from(dom.childNodes).map(child => 
          child.textContent
        ).join("\n")
        break
      case Gemini.type.LIST: 
        return Array.from(dom.children).map(child => 
          child.textContent
        ).join("\n")
        break
      case Gemini.type.LINK: 
        const {href, content} = Gemini.PARSE_LINK.exec(dom.textContent).groups
        return `${href || dom.href} ${content}`
        break
      case Gemini.type.PREFORMATTED: 
        return dom.textContent
        break
      default:
        return dom.innerHTML.replace(/<br>/g, "\n")
    }
  }
  get lines() {
    return Array.from(this.root.children)
      .filter(el => Object.values(Gemini.type).includes(el.nodeName))
      .map(Gemini.line)
  }
  set lines(lines) {
    this.root.textContent = ""
    this.root.append(...lines.map(line => line.dom))
  } 
  get source() { return this.lines.map(line => line.gmi).join("\n") }
  set source(gmi) {
    this.lines = Gemini.parse(gmi).map(([content, type]) => 
      Gemini.line({type, content}))
  }
  download() {
    const el = document.createElement('a')
    el.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(this.source))
    el.setAttribute('download', `${this.lines[0].content.replace(/\s/g, "_")}.gmi`)
    el.style.display = 'none'
    document.body.appendChild(el); el.click(); document.body.removeChild(el)
  }

  // TODO: Refactor all of this into something cohesive 
  static PARSE_LINK = /((?<href>[^\s]+\/\/[^\s]+)\s)?(?<content>.+)/
  static type = {
    TEXT: "P",
    LINK: "A",
    LIST: "UL",
    QUOTE: "BLOCKQUOTE",
    PREFORMATTED: "PRE",
    H1: "H1",
    H2: "H2",
    H3: "H3",
  } 
  static syntax = {
    [Gemini.type.TEXT]: "",
    [Gemini.type.LINK]: "=>",
    [Gemini.type.LIST]: "*",
    [Gemini.type.QUOTE]: ">",
    [Gemini.type.PREFORMATTED]: "```",
    [Gemini.type.H1]: "#",
    [Gemini.type.H2]: "##",
    [Gemini.type.H3]: "###",
  }
  static get nodeName() {
    return Object.entries(Gemini.syntax).reduce((flipped, entry) => {
      const [key, value] = entry
      flipped[value] = key
      return flipped
    }, {})
  }
  static parse(gmi) {
    let lines = gmi.split("\n")
    let parsed = [] 
    while (lines.length) {
      const line = lines.shift()
      const syntax = /^[^\s]+/
      const type = syntax.test(line) ? Gemini.nodeName[line.match(syntax)[0]] || Gemini.type.TEXT : Gemini.type.TEXT
      let content = ""
      let until 
      switch (type) {
        case Gemini.type.PREFORMATTED:
          until = lines.findIndex(line => line === Gemini.syntax[Gemini.type.PREFORMATTED])
          content = lines.slice(0, until).join("\n")
          lines = lines.slice(until + 1)
          break
        case Gemini.type.QUOTE:
          until = lines.findIndex(line => /[^>]/.test(line))
          content = [line, ...lines].slice(0, until + 1).map(line => line.replace("> ", "")).join("\n")
          lines = lines.slice(until)
          break
        case Gemini.type.LIST:
          until = lines.findIndex(line => /[^\*]/.test(line))
          content = [line, ...lines].slice(0, until + 2).map(line => line.replace("* ", "")).join("\n")
          lines = lines.slice(until + 1)
          break
        case Gemini.type.TEXT:
          content = line
          break
        default:
          content = line.replace(syntax, "")
      }
      parsed.push([content.length === 0 ? "\n" : content.trim(), type])
    }
    return parsed
  }
  constructor(root) {
    this.root = root
    // TODO: reference gmi2html implementation, fix these quirks
    for (let el of this.root.childNodes) {
      if (el.nodeName === "BR") {
        let empty = document.createElement(Gemini.type.TEXT)
        empty.innerHTML = "<br>"
        el.replaceWith(empty)
      }
      if (el.nodeName === "P" && el.firstChild.nodeName === Gemini.type.LINK) {
        el.replaceWith(el.firstChild)
      }
    }
  }
}