'use strict'

module.exports = factory

// Construct a tokenizer.  This creates both `tokenizeInline` and `tokenizeBlock`.
function factory(type) {
  return tokenize

  // Tokenizer for a bound `type`.
  function tokenize(value, location) {
    var self = this
    var offset = self.offset
    var tokens = []
    var methods = self[type + 'Methods']
    var tokenizers = self[type + 'Tokenizers']
    var line = location.line
    var column = location.column
    var index
    var length
    var method
    var name
    var matched
    var valueLength

    // Trim white space only lines.
    if (!value) {
      return tokens
    }

    // Expose on `eat`.
    eat.now = now
    eat.file = self.file

    // Sync initial offset.
    updatePosition('')

    // Iterate over `value`, and iterate over all tokenizers.  When one eats
    // something, re-iterate with the remaining value.  If no tokenizer eats,
    // something failed (should not happen) and an exception is thrown.
    while (value) {
      index = -1
      length = methods.length
      matched = false

      while (++index < length) {
        name = methods[index]
        method = tokenizers[name]

        // Previously, we had constructs such as footnotes and YAML that used
        // these properties.
        // Those are now external (plus there are userland extensions), that may
        // still use them.
        if (
          method &&
          /* istanbul ignore next */ (!method.onlyAtStart || self.atStart) &&
          /* istanbul ignore next */ (!method.notInList || !self.inList) &&
          /* istanbul ignore next */ (!method.notInBlock || !self.inBlock) &&
          (!method.notInLink || !self.inLink)
        ) {
          valueLength = value.length

          method.apply(self, [eat, value])

          matched = valueLength !== value.length

          if (matched) {
            break
          }
        }
      }

      /* istanbul ignore if */
      if (!matched) {
        self.file.fail(new Error('Infinite loop'), eat.now())
      }
    }

    self.eof = now()

    return tokens

    // Update line, column, and offset based on `value`.
    function updatePosition(subvalue) {
      var lastIndex = -1
      var index = subvalue.indexOf('\n')

      while (index !== -1) {
        line++
        lastIndex = index
        index = subvalue.indexOf('\n', index + 1)
      }

      if (lastIndex === -1) {
        column += subvalue.length
      } else {
        column = subvalue.length - lastIndex
      }

      if (line in offset) {
        if (lastIndex !== -1) {
          column += offset[line]
        } else if (column <= offset[line]) {
          column = offset[line] + 1
        }
      }
    }

    // Get offset.  Called before the first character is eaten to retrieve the
    // range’s offsets.
    function getOffset() {
      var indentation = []
      var pos = line + 1

      // Done.  Called when the last character is eaten to retrieve the range’s
      // offsets.
      return function () {
        var last = line + 1

        while (pos < last) {
          indentation.push((offset[pos] || 0) + 1)

          pos++
        }

        return indentation
      }
    }

    // Get the current position.
    function now() {
      var pos = {line: line, column: column}

      pos.offset = self.toOffset(pos)

      return pos
    }

    // Store position information for a node.
    function Position(start) {
      this.start = start
      this.end = now()
    }

    // Throw when a value is incorrectly eaten.  This shouldn’t happen but will
    // throw on new, incorrect rules.
    function validateEat(subvalue) {
      /* istanbul ignore if */
      if (value.slice(0, subvalue.length) !== subvalue) {
        // Capture stack-trace.
        self.file.fail(
          new Error(
            'Incorrectly eaten value: please report this warning on https://git.io/vg5Ft'
          ),
          now()
        )
      }
    }

    // Mark position and patch `node.position`.
    function position() {
      var before = now()

      return update

      // Add the position to a node.
      function update(node, indent) {
        var previous = node.position
        var start = previous ? previous.start : before
        var combined = []
        var n = previous && previous.end.line
        var l = before.line

        node.position = new Position(start)

        // If there was already a `position`, this node was merged.  Fixing
        // `start` wasn’t hard, but the indent is different.  Especially
        // because some information, the indent between `n` and `l` wasn’t
        // tracked.  Luckily, that space is (should be?) empty, so we can
        // safely check for it now.
        if (previous && indent && previous.indent) {
          combined = previous.indent

          if (n < l) {
            while (++n < l) {
              combined.push((offset[n] || 0) + 1)
            }

            combined.push(before.column)
          }

          indent = combined.concat(indent)
        }

        node.position.indent = indent || []

        return node
      }
    }

    // Add `node` to `parent`s children or to `tokens`.  Performs merges where
    // possible.
    function add(node, parent) {
      var children = parent ? parent.children : tokens
      var previous = children[children.length - 1]
      var fn

      if (
        previous &&
        node.type === previous.type &&
        (node.type === 'text' || node.type === 'blockquote') &&
        mergeable(previous) &&
        mergeable(node)
      ) {
        fn = node.type === 'text' ? mergeText : mergeBlockquote
        node = fn.call(self, previous, node)
      }

      if (node !== previous) {
        children.push(node)
      }

      if (self.atStart && tokens.length !== 0) {
        self.exitStart()
      }

      return node
    }

    // Remove `subvalue` from `value`.  `subvalue` must be at the start of
    // `value`.
    function eat(subvalue) {
      var indent = getOffset()
      var pos = position()
      var current = now()

      validateEat(subvalue)

      apply.reset = reset
      reset.test = test
      apply.test = test

      value = value.slice(subvalue.length)

      updatePosition(subvalue)

      indent = indent()

      return apply

      // Add the given arguments, add `position` to the returned node, and
      // return the node.
      function apply(node, parent) {
        return pos(add(pos(node), parent), indent)
      }

      // Functions just like apply, but resets the content: the line and
      // column are reversed, and the eaten value is re-added.   This is
      // useful for nodes with a single type of content, such as lists and
      // tables.  See `apply` above for what parameters are expected.
      function reset() {
        var node = apply.apply(null, arguments)

        line = current.line
        column = current.column
        value = subvalue + value

        return node
      }

      // Test the position, after eating, and reverse to a not-eaten state.
      function test() {
        var result = pos({})

        line = current.line
        column = current.column
        value = subvalue + value

        return result.position
      }
    }
  }
}

// Check whether a node is mergeable with adjacent nodes.
function mergeable(node) {
  var start
  var end

  if (node.type !== 'text' || !node.position) {
    return true
  }

  start = node.position.start
  end = node.position.end

  // Only merge nodes which occupy the same size as their `value`.
  return (
    start.line !== end.line || end.column - start.column === node.value.length
  )
}

// Merge two text nodes: `node` into `prev`.
function mergeText(previous, node) {
  previous.value += node.value

  return previous
}

// Merge two blockquotes: `node` into `prev`, unless in CommonMark or gfm modes.
function mergeBlockquote(previous, node) {
  if (this.options.commonmark || this.options.gfm) {
    return node
  }

  previous.children = previous.children.concat(node.children)

  return previous
}