feat: use incremental instead of full content updates

src/app.ts

@@ -11,7 +11,7 @@ const main = async () => {
         triggerCharacters: ["{", "(", ")", "=", ">", " ", ",", ":", ".", "<", "/"]
       },
       textDocumentSync: {
-        change: 1,
+        change: 2,
       }
     }
   })

src/lsp.ts

@@ -19,8 +19,8 @@ enum DiagnosticSeverity {
 }
 
 type Position = {
-  start: number,
-  end: number
+  line: number,
+  character: number
 }
 
 type Range = {
@@ -81,25 +81,47 @@ class Service {
 
     this.on(Event.DidOpen, ({ ctx, request }) => {
       ctx.currentUri = request.params.textDocument.uri
+      ctx.contents = request.params.textDocument.text
+      ctx.language = request.params.textDocument.languageId
+      ctx.contentVersion = 0
     })
 
-    this.on(Event.Shutdown, ({ ctx, request }) => {
+    this.on(Event.Shutdown, () => {
       log("received shutdown request")
       process.exit(0)
     })
 
-    this.on(Event.DidOpen, async ({ ctx, request }) => {
-      ctx.contents = request.params.textDocument.text
-      ctx.language = request.params.textDocument.languageId
-      ctx.contentVersion = 0
-    })
-
     this.on(Event.DidChange, async ({ ctx, request }) => {
-      ctx.contents = request.params.contentChanges[0].text
+      request.params.contentChanges.forEach((change) => {
+        this.positionalUpdate(change.text, change.range)
+      })
+
       ctx.contentVersion = request.params.textDocument.version
     })
   }
 
+  positionalUpdate(text: string, range: Range) {
+    const lines = this.contents.split("\n")
+    const start = range.start.line
+    const end = range.end.line
+    const startLine = lines[start]
+    const endLine = lines[end]
+    const startLineStart = startLine.substring(0, range.start.character)
+    const endLineEnd = endLine.substring(range.end.character)
+    const newLines = [startLineStart + text + endLineEnd]
+
+    const newContents = lines.reduce((acc, line, index) => {
+      if (index < start || index > end) {
+        acc.push(line)
+      } else if (index === start) {
+        acc.push(newLines[0])
+      }
+      return acc
+    }, [])
+
+    this.contents = newContents.join("\n")
+  }
+
   on(event: string, callback: (request: EventRequest) => void) {
     const parent = this