mirror of
https://github.com/overleaf/overleaf.git
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498 lines
No EOL
19 KiB
CoffeeScript
498 lines
No EOL
19 KiB
CoffeeScript
load = (EventEmitter) ->
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class RangesTracker extends EventEmitter
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# The purpose of this class is to track a set of inserts and deletes to a document, like
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# track changes in Word. We store these as a set of ShareJs style ranges:
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# {i: "foo", p: 42} # Insert 'foo' at offset 42
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# {d: "bar", p: 37} # Delete 'bar' at offset 37
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# We only track the inserts and deletes, not the whole document, but by being given all
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# updates that are applied to a document, we can update these appropriately.
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#
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# Note that the set of inserts and deletes we store applies to the document as-is at the moment.
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# So inserts correspond to text which is in the document, while deletes correspond to text which
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# is no longer there, so their lengths do not affect the position of later offsets.
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# E.g.
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# this is the current text of the document
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# |-----| |
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# {i: "current ", p:12} -^ ^- {d: "old ", p: 31}
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#
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# Track changes rules (should be consistent with Word):
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# * When text is inserted at a delete, the text goes to the left of the delete
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# I.e. "foo|bar" -> "foobaz|bar", where | is the delete, and 'baz' is inserted
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# * Deleting content flagged as 'inserted' does not create a new delete marker, it only
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# removes the insert marker. E.g.
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# * "abdefghijkl" -> "abfghijkl" when 'de' is deleted. No delete marker added
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# |---| <- inserted |-| <- inserted
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# * Deletes overlapping regular text and inserted text will insert a delete marker for the
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# regular text:
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# "abcdefghijkl" -> "abcdejkl" when 'fghi' is deleted
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# |----| |--||
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# ^- inserted 'bcdefg' \ ^- deleted 'hi'
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# \--inserted 'bcde'
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# * Deletes overlapping other deletes are merged. E.g.
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# "abcghijkl" -> "ahijkl" when 'bcg is deleted'
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# | <- delete 'def' | <- delete 'bcdefg'
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# * Deletes by another user will consume deletes by the first user
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# * Inserts by another user will not combine with inserts by the first user. If they are in the
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# middle of a previous insert by the first user, the original insert will be split into two.
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constructor: (@changes = [], @comments = []) ->
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@setIdSeed(RangesTracker.generateIdSeed())
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getIdSeed: () ->
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return @id_seed
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setIdSeed: (seed) ->
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@id_seed = seed
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@id_increment = 0
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@generateIdSeed: () ->
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# Generate a the first 18 characters of Mongo ObjectId, leaving 6 for the increment part
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# Reference: https://github.com/dreampulse/ObjectId.js/blob/master/src/main/javascript/Objectid.js
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pid = Math.floor(Math.random() * (32767)).toString(16)
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machine = Math.floor(Math.random() * (16777216)).toString(16)
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timestamp = Math.floor(new Date().valueOf() / 1000).toString(16)
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return '00000000'.substr(0, 8 - timestamp.length) + timestamp +
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'000000'.substr(0, 6 - machine.length) + machine +
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'0000'.substr(0, 4 - pid.length) + pid
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@generateId: () ->
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@generateIdSeed() + "000001"
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newId: () ->
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@id_increment++
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increment = @id_increment.toString(16)
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id = @id_seed + '000000'.substr(0, 6 - increment.length) + increment;
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return id
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getComment: (comment_id) ->
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comment = null
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for c in @comments
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if c.id == comment_id
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comment = c
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break
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return comment
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removeCommentId: (comment_id) ->
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comment = @getComment(comment_id)
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return if !comment?
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@comments = @comments.filter (c) -> c.id != comment_id
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@emit "comment:removed", comment
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getChange: (change_id) ->
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change = null
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for c in @changes
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if c.id == change_id
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change = c
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break
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return change
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removeChangeId: (change_id) ->
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change = @getChange(change_id)
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return if !change?
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@_removeChange(change)
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applyOp: (op, metadata = {}) ->
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metadata.ts ?= new Date()
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# Apply an op that has been applied to the document to our changes to keep them up to date
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if op.i?
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@applyInsertToChanges(op, metadata)
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@applyInsertToComments(op)
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else if op.d?
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@applyDeleteToChanges(op, metadata)
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@applyDeleteToComments(op)
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else if op.c?
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@addComment(op, metadata)
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else
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throw new Error("unknown op type")
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addComment: (op, metadata) ->
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# TODO: Don't allow overlapping comments?
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@comments.push comment = {
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id: op.t or @newId()
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op: # Copy because we'll modify in place
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c: op.c
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p: op.p
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t: op.t
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metadata
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}
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@emit "comment:added", comment
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return comment
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applyInsertToComments: (op) ->
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for comment in @comments
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if op.p <= comment.op.p
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comment.op.p += op.i.length
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@emit "comment:moved", comment
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else if op.p < comment.op.p + comment.op.c.length
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offset = op.p - comment.op.p
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comment.op.c = comment.op.c[0..(offset-1)] + op.i + comment.op.c[offset...]
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@emit "comment:moved", comment
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applyDeleteToComments: (op) ->
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op_start = op.p
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op_length = op.d.length
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op_end = op.p + op_length
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for comment in @comments
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comment_start = comment.op.p
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comment_end = comment.op.p + comment.op.c.length
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comment_length = comment_end - comment_start
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if op_end <= comment_start
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# delete is fully before comment
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comment.op.p -= op_length
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@emit "comment:moved", comment
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else if op_start >= comment_end
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# delete is fully after comment, nothing to do
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else
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# delete and comment overlap
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if op_start <= comment_start
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remaining_before = ""
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else
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remaining_before = comment.op.c.slice(0, op_start - comment_start)
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if op_end >= comment_end
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remaining_after = ""
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else
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remaining_after = comment.op.c.slice(op_end - comment_start)
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# Check deleted content matches delete op
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deleted_comment = comment.op.c.slice(remaining_before.length, comment_length - remaining_after.length)
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offset = Math.max(0, comment_start - op_start)
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deleted_op_content = op.d.slice(offset).slice(0, deleted_comment.length)
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if deleted_comment != deleted_op_content
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throw new Error("deleted content does not match comment content")
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comment.op.p = Math.min(comment_start, op_start)
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comment.op.c = remaining_before + remaining_after
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@emit "comment:moved", comment
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applyInsertToChanges: (op, metadata) ->
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op_start = op.p
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op_length = op.i.length
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op_end = op.p + op_length
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already_merged = false
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previous_change = null
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moved_changes = []
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remove_changes = []
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new_changes = []
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for change, i in @changes
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change_start = change.op.p
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if change.op.d?
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# Shift any deletes after this along by the length of this insert
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if op_start < change_start
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change.op.p += op_length
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moved_changes.push change
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else if op_start == change_start
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# If the insert matches the start of the delete, just remove it from the delete instead
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if change.op.d.length >= op.i.length and change.op.d.slice(0, op.i.length) == op.i
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change.op.d = change.op.d.slice(op.i.length)
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change.op.p += op.i.length
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if change.op.d == ""
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remove_changes.push change
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else
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moved_changes.push change
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already_merged = true
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else
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change.op.p += op_length
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moved_changes.push change
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else if change.op.i?
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change_end = change_start + change.op.i.length
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is_change_overlapping = (op_start >= change_start and op_start <= change_end)
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# Only merge inserts if they are from the same user
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is_same_user = metadata.user_id == change.metadata.user_id
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# If this is an insert op at the end of an existing insert with a delete following, and it cancels out the following
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# delete then we shouldn't append it to this insert, but instead only cancel the following delete.
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# E.g.
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# foo|<--- about to insert 'bar' here
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# inserted 'foo' --^ ^-- deleted 'bar'
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# should become just 'foo' not 'foobar' (with the delete marker disappearing), .
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next_change = @changes[i+1]
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is_op_adjacent_to_next_delete = next_change? and next_change.op.d? and op.p == change_end and next_change.op.p == op.p
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will_op_cancel_next_delete = is_op_adjacent_to_next_delete and next_change.op.d == op.i
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# If there is a delete at the start of the insert, and we're inserting
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# at the start, we SHOULDN'T merge since the delete acts as a partition.
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# The previous op will be the delete, but it's already been shifted by this insert
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#
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# I.e.
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# Originally: |-- existing insert --|
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# | <- existing delete at same offset
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#
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# Now: |-- existing insert --| <- not shifted yet
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# |-- this insert --|| <- existing delete shifted along to end of this op
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#
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# After: |-- existing insert --|
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# |-- this insert --|| <- existing delete
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#
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# Without the delete, the inserts would be merged.
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is_insert_blocked_by_delete = (previous_change? and previous_change.op.d? and previous_change.op.p == op_end)
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# If the insert is overlapping another insert, either at the beginning in the middle or touching the end,
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# then we merge them into one.
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if @track_changes and
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is_change_overlapping and
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!is_insert_blocked_by_delete and
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!already_merged and
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!will_op_cancel_next_delete and
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is_same_user
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offset = op_start - change_start
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change.op.i = change.op.i.slice(0, offset) + op.i + change.op.i.slice(offset)
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change.metadata.ts = metadata.ts
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already_merged = true
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moved_changes.push change
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else if op_start <= change_start
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# If we're fully before the other insert we can just shift the other insert by our length.
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# If they are touching, and should have been merged, they will have been above.
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# If not merged above, then it must be blocked by a delete, and will be after this insert, so we shift it along as well
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change.op.p += op_length
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moved_changes.push change
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else if (!is_same_user or !@track_changes) and change_start < op_start < change_end
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# This user is inserting inside a change by another user, so we need to split the
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# other user's change into one before and after this one.
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offset = op_start - change_start
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before_content = change.op.i.slice(0, offset)
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after_content = change.op.i.slice(offset)
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# The existing change can become the 'before' change
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change.op.i = before_content
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moved_changes.push change
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# Create a new op afterwards
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after_change = {
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op: {
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i: after_content
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p: change_start + offset + op_length
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}
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metadata: {}
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}
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after_change.metadata[key] = value for key, value of change.metadata
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new_changes.push after_change
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previous_change = change
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if @track_changes and !already_merged
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@_addOp op, metadata
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for {op, metadata} in new_changes
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@_addOp op, metadata
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for change in remove_changes
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@_removeChange change
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if moved_changes.length > 0
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@emit "changes:moved", moved_changes
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applyDeleteToChanges: (op, metadata) ->
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op_start = op.p
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op_length = op.d.length
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op_end = op.p + op_length
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remove_changes = []
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moved_changes = []
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# We might end up modifying our delete op if it merges with existing deletes, or cancels out
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# with an existing insert. Since we might do multiple modifications, we record them and do
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# all the modifications after looping through the existing changes, so as not to mess up the
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# offset indexes as we go.
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op_modifications = []
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for change in @changes
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if change.op.i?
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change_start = change.op.p
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change_end = change_start + change.op.i.length
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if op_end <= change_start
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# Shift ops after us back by our length
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change.op.p -= op_length
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moved_changes.push change
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else if op_start >= change_end
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# Delete is after insert, nothing to do
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else
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# When the new delete overlaps an insert, we should remove the part of the insert that
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# is now deleted, and also remove the part of the new delete that overlapped. I.e.
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# the two cancel out where they overlap.
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if op_start >= change_start
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# |-- existing insert --|
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# insert_remaining_before -> |.....||-- new delete --|
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delete_remaining_before = ""
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insert_remaining_before = change.op.i.slice(0, op_start - change_start)
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else
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# delete_remaining_before -> |.....||-- existing insert --|
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# |-- new delete --|
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delete_remaining_before = op.d.slice(0, change_start - op_start)
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insert_remaining_before = ""
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if op_end <= change_end
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# |-- existing insert --|
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# |-- new delete --||.....| <- insert_remaining_after
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delete_remaining_after = ""
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insert_remaining_after = change.op.i.slice(op_end - change_start)
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else
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# |-- existing insert --||.....| <- delete_remaining_after
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# |-- new delete --|
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delete_remaining_after = op.d.slice(change_end - op_start)
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insert_remaining_after = ""
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insert_remaining = insert_remaining_before + insert_remaining_after
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if insert_remaining.length > 0
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change.op.i = insert_remaining
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change.op.p = Math.min(change_start, op_start)
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change.metadata.ts = metadata.ts
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moved_changes.push change
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else
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remove_changes.push change
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# We know what we want to preserve of our delete op before (delete_remaining_before) and what we want to preserve
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# afterwards (delete_remaining_before). Now we need to turn that into a modification which deletes the
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# chunk in the middle not covered by these.
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delete_removed_length = op.d.length - delete_remaining_before.length - delete_remaining_after.length
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delete_removed_start = delete_remaining_before.length
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modification = {
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d: op.d.slice(delete_removed_start, delete_removed_start + delete_removed_length)
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p: delete_removed_start
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}
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if modification.d.length > 0
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op_modifications.push modification
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else if change.op.d?
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change_start = change.op.p
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if op_end < change_start or (!@track_changes and op_end == change_start)
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# Shift ops after us back by our length.
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# If we're tracking changes, it must be strictly before, since we'll merge
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# below if they are touching. Otherwise, touching is fine.
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change.op.p -= op_length
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moved_changes.push change
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else if op_start <= change_start <= op_end
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if @track_changes
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# If we overlap a delete, add it in our content, and delete the existing change.
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# It's easier to do it this way, rather than modifying the existing delete in case
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# we overlap many deletes and we'd need to track that. We have a workaround to
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# update the delete in place if possible below.
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offset = change_start - op_start
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op_modifications.push { i: change.op.d, p: offset }
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remove_changes.push change
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else
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change.op.p = op_start
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moved_changes.push change
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# Copy rather than modify because we still need to apply it to comments
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op = {
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p: op.p
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d: @_applyOpModifications(op.d, op_modifications)
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}
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for change in remove_changes
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# This is a bit of hack to avoid removing one delete and replacing it with another.
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# If we don't do this, it causes the UI to flicker
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if op.d.length > 0 and change.op.d? and op.p <= change.op.p <= op.p + op.d.length
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change.op.p = op.p
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change.op.d = op.d
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change.metadata = metadata
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moved_changes.push change
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op.d = "" # stop it being added
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else
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@_removeChange change
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if @track_changes and op.d.length > 0
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@_addOp op, metadata
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else
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# It's possible that we deleted an insert between two other inserts. I.e.
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# If we delete 'user_2 insert' in:
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# |-- user_1 insert --||-- user_2 insert --||-- user_1 insert --|
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# it becomes:
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# |-- user_1 insert --||-- user_1 insert --|
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# We need to merge these together again
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results = @_scanAndMergeAdjacentUpdates()
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moved_changes = moved_changes.concat(results.moved_changes)
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for change in results.remove_changes
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@_removeChange change
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moved_changes = moved_changes.filter (c) -> c != change
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if moved_changes.length > 0
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@emit "changes:moved", moved_changes
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_addOp: (op, metadata) ->
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change = {
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id: @newId()
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op: @_clone(op) # Don't take a reference to the existing op since we'll modify this in place with future changes
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metadata: @_clone(metadata)
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}
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@changes.push change
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# Keep ops in order of offset, with deletes before inserts
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@changes.sort (c1, c2) ->
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result = c1.op.p - c2.op.p
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if result != 0
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return result
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else if c1.op.i? and c2.op.d?
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return 1
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else
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return -1
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if op.d?
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@emit "delete:added", change
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else if op.i?
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@emit "insert:added", change
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_removeChange: (change) ->
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@changes = @changes.filter (c) -> c.id != change.id
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if change.op.d?
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@emit "delete:removed", change
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else if change.op.i?
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@emit "insert:removed", change
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_applyOpModifications: (content, op_modifications) ->
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# Put in descending position order, with deleting first if at the same offset
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# (Inserting first would modify the content that the delete will delete)
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op_modifications.sort (a, b) ->
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result = b.p - a.p
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if result != 0
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return result
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else if a.i? and b.d?
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return 1
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else
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return -1
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for modification in op_modifications
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if modification.i?
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content = content.slice(0, modification.p) + modification.i + content.slice(modification.p)
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else if modification.d?
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if content.slice(modification.p, modification.p + modification.d.length) != modification.d
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throw new Error("deleted content does not match. content: #{JSON.stringify(content)}; modification: #{JSON.stringify(modification)}")
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content = content.slice(0, modification.p) + content.slice(modification.p + modification.d.length)
|
|
return content
|
|
|
|
_scanAndMergeAdjacentUpdates: () ->
|
|
# This should only need calling when deleting an update between two
|
|
# other updates. There's no other way to get two adjacent updates from the
|
|
# same user, since they would be merged on insert.
|
|
previous_change = null
|
|
remove_changes = []
|
|
moved_changes = []
|
|
for change in @changes
|
|
if previous_change?.op.i? and change.op.i?
|
|
previous_change_end = previous_change.op.p + previous_change.op.i.length
|
|
previous_change_user_id = previous_change.metadata.user_id
|
|
change_start = change.op.p
|
|
change_user_id = change.metadata.user_id
|
|
if previous_change_end == change_start and previous_change_user_id == change_user_id
|
|
remove_changes.push change
|
|
previous_change.op.i += change.op.i
|
|
moved_changes.push previous_change
|
|
else if previous_change?.op.d? and change.op.d? and previous_change.op.p == change.op.p
|
|
# Merge adjacent deletes
|
|
previous_change.op.d += change.op.d
|
|
remove_changes.push change
|
|
moved_changes.push previous_change
|
|
else # Only update to the current change if we haven't removed it.
|
|
previous_change = change
|
|
return { moved_changes, remove_changes }
|
|
|
|
_clone: (object) ->
|
|
clone = {}
|
|
(clone[k] = v for k,v of object)
|
|
return clone
|
|
|
|
if define?
|
|
define ["utils/EventEmitter"], load
|
|
else
|
|
EventEmitter = require("events").EventEmitter
|
|
module.exports = load(EventEmitter) |