import { loadMode } from "../display/mode_state"
import { regChange } from "../display/view_tracking"
import { Line, updateLine } from "../line/line_data"
import { findMaxLine } from "../line/spans"
import { getLine } from "../line/utils_line"
import { estimateLineHeights } from "../measurement/position_measurement"
import { lst } from "../util/misc"
import { signalLater } from "../util/operation_group"

// DOCUMENT DATA STRUCTURE

// By default, updates that start and end at the beginning of a line
// are treated specially, in order to make the association of line
// widgets and marker elements with the text behave more intuitive.
export function isWholeLineUpdate(doc, change) {
  return change.from.ch == 0 && change.to.ch == 0 && lst(change.text) == "" &&
    (!doc.cm || doc.cm.options.wholeLineUpdateBefore)
}

// Perform a change on the document data structure.
export function updateDoc(doc, change, markedSpans, estimateHeight) {
  function spansFor(n) {return markedSpans ? markedSpans[n] : null}
  function update(line, text, spans) {
    updateLine(line, text, spans, estimateHeight)
    signalLater(line, "change", line, change)
  }
  function linesFor(start, end) {
    let result = []
    for (let i = start; i < end; ++i)
      result.push(new Line(text[i], spansFor(i), estimateHeight))
    return result
  }

  let from = change.from, to = change.to, text = change.text
  let firstLine = getLine(doc, from.line), lastLine = getLine(doc, to.line)
  let lastText = lst(text), lastSpans = spansFor(text.length - 1), nlines = to.line - from.line

  // Adjust the line structure
  if (change.full) {
    doc.insert(0, linesFor(0, text.length))
    doc.remove(text.length, doc.size - text.length)
  } else if (isWholeLineUpdate(doc, change)) {
    // This is a whole-line replace. Treated specially to make
    // sure line objects move the way they are supposed to.
    let added = linesFor(0, text.length - 1)
    update(lastLine, lastLine.text, lastSpans)
    if (nlines) doc.remove(from.line, nlines)
    if (added.length) doc.insert(from.line, added)
  } else if (firstLine == lastLine) {
    if (text.length == 1) {
      update(firstLine, firstLine.text.slice(0, from.ch) + lastText + firstLine.text.slice(to.ch), lastSpans)
    } else {
      let added = linesFor(1, text.length - 1)
      added.push(new Line(lastText + firstLine.text.slice(to.ch), lastSpans, estimateHeight))
      update(firstLine, firstLine.text.slice(0, from.ch) + text[0], spansFor(0))
      doc.insert(from.line + 1, added)
    }
  } else if (text.length == 1) {
    update(firstLine, firstLine.text.slice(0, from.ch) + text[0] + lastLine.text.slice(to.ch), spansFor(0))
    doc.remove(from.line + 1, nlines)
  } else {
    update(firstLine, firstLine.text.slice(0, from.ch) + text[0], spansFor(0))
    update(lastLine, lastText + lastLine.text.slice(to.ch), lastSpans)
    let added = linesFor(1, text.length - 1)
    if (nlines > 1) doc.remove(from.line + 1, nlines - 1)
    doc.insert(from.line + 1, added)
  }

  signalLater(doc, "change", doc, change)
}

// Call f for all linked documents.
export function linkedDocs(doc, f, sharedHistOnly) {
  function propagate(doc, skip, sharedHist) {
    if (doc.linked) for (let i = 0; i < doc.linked.length; ++i) {
      let rel = doc.linked[i]
      if (rel.doc == skip) continue
      let shared = sharedHist && rel.sharedHist
      if (sharedHistOnly && !shared) continue
      f(rel.doc, shared)
      propagate(rel.doc, doc, shared)
    }
  }
  propagate(doc, null, true)
}

// Attach a document to an editor.
export function attachDoc(cm, doc) {
  if (doc.cm) throw new Error("This document is already in use.")
  cm.doc = doc
  doc.cm = cm
  estimateLineHeights(cm)
  loadMode(cm)
  if (!cm.options.lineWrapping) findMaxLine(cm)
  cm.options.mode = doc.modeOption
  regChange(cm)
}

