1 files changed, 99 insertions, 0 deletions
diff --git a/script/text-merger.lua b/script/text-merger.lua
new file mode 100644
index 00000000..9e01ba1c
--- /dev/null
+++ b/script/text-merger.lua
@@ -0,0 +1,99 @@
+local files = require 'files'
+local util  = require 'utility'
+
+local function splitRows(text)
+    local rows = {}
+    for line in util.eachLine(text, true) do
+        rows[#rows+1] = line
+    end
+    return rows
+end
+
+local function getLeft(text, char)
+    local left
+    local length = util.utf8Len(text)
+
+    if char == 0 then
+        left = ''
+    elseif char >= length then
+        left = text
+    else
+        left = text:sub(1, utf8.offset(text, char + 1) - 1)
+    end
+
+    return left
+end
+
+local function getRight(text, char)
+    local right
+    local length = util.utf8Len(text)
+
+    if char == 0 then
+        right = text
+    elseif char >= length then
+        right = ''
+    else
+        right = text:sub(utf8.offset(text, char + 1))
+    end
+
+    return right
+end
+
+local function mergeRows(rows, change)
+    local startLine = change.range['start'].line + 1
+    local startChar = change.range['start'].character
+    local endLine   = change.range['end'].line + 1
+    local endChar   = change.range['end'].character
+
+    local insertRows = splitRows(change.text)
+    -- 先把双方的行数调整成一致
+    local delta = #insertRows - (endLine - startLine + 1)
+    if delta ~= 0 then
+        table.move(rows, endLine, #rows, endLine + delta)
+        -- 如果行数变少了，要清除多余的行
+        if delta < 0 then
+            for i = #rows, #rows + delta + 1, -1 do
+                rows[i] = nil
+            end
+        end
+    end
+    -- 先处理第一行和最后一行
+    local newEndLine = startLine + #insertRows - 1
+    local left  = getLeft(rows[startLine],   startChar)
+    local right = getRight(rows[newEndLine], endChar)
+    if startLine == newEndLine then
+        rows[startLine]  = left .. insertRows[1] .. right
+    else
+        rows[startLine]  = left .. insertRows[1]
+        rows[newEndLine] = insertRows[#insertRows] .. right
+    end
+    -- 修改中间的每一行
+    for i = 2, #insertRows - 1 do
+        local currentLine = startLine + i - 1
+        local insertText  = insertRows[i]
+        rows[currentLine] = insertText
+    end
+end
+
+return function (uri, changes)
+    local text
+    for _, change in ipairs(changes) do
+        if change.range then
+            local rows = files.getCachedRows(uri)
+            if not rows then
+                text = text or files.getOriginText(uri)
+                rows = splitRows(text)
+            end
+            mergeRows(rows, change)
+            files.setCachedRows(uri, rows)
+        else
+            files.setCachedRows(uri, nil)
+            text = change.text
+        end
+    end
+    local rows = files.getCachedRows(uri)
+    if rows then
+        text = table.concat(rows)
+    end
+    return text
+end