feat(cdl): add CDL event handler parsing and snippet support

This adds a small DSL-aware helper to extract CDL event
declarations and generate a ready-to-use snippet. It also
extends hover support to show the snippet and parameter
hints for CDL events, improving developer productivity.

- Generate a MOM event handler scaffold and local vars
- Hover shows the generated snippet and mom_ parameter hints

client/src/common/cdlEventHandler.ts

@@ -0,0 +1,116 @@
+export interface CdlEventHandler {
+    eventName: string
+    parameterNames: string[]
+}
+
+function structuralCode(line: string): string {
+    let result = ""
+    let inString = false
+    let escaped = false
+
+    for (const character of line) {
+        if (escaped) {
+            escaped = false
+            result += inString ? " " : character
+            continue
+        }
+        if (character === "\\") {
+            escaped = true
+            result += inString ? " " : character
+            continue
+        }
+        if (character === '"') {
+            inString = !inString
+            result += " "
+            continue
+        }
+        if (character === "#" && !inString) {
+            break
+        }
+        result += inString ? " " : character
+    }
+
+    return result
+}
+
+function braceDelta(line: string): number {
+    let delta = 0
+    for (const character of structuralCode(line)) {
+        if (character === "{") {
+            delta += 1
+        } else if (character === "}") {
+            delta -= 1
+        }
+    }
+    return delta
+}
+
+export function cdlEventHandlerAtLine(
+    source: string,
+    declarationLine: number
+): CdlEventHandler | undefined {
+    const lines = source.split(/\r?\n/)
+    const declaration = lines[declarationLine]
+    if (declaration === undefined) {
+        return undefined
+    }
+
+    const eventMatch = /^\s*EVENT\s+([^\s{]+)/.exec(structuralCode(declaration))
+    if (!eventMatch) {
+        return undefined
+    }
+
+    const parameterNames: string[] = []
+    let eventOpened = false
+    let depth = 0
+
+    for (let lineNumber = declarationLine; lineNumber < lines.length; lineNumber++) {
+        const line = lines[lineNumber]
+        const code = structuralCode(line)
+
+        if (eventOpened && depth === 1) {
+            const parameterMatch = /^\s*PARAM\s+([^\s{]+)/.exec(code)
+            if (parameterMatch) {
+                parameterNames.push(parameterMatch[1])
+            }
+        }
+
+        const delta = braceDelta(line)
+        if (!eventOpened && delta > 0) {
+            eventOpened = true
+        }
+        if (eventOpened) {
+            depth += delta
+            if (depth <= 0) {
+                break
+            }
+        }
+    }
+
+    return {
+        eventName: eventMatch[1],
+        parameterNames
+    }
+}
+
+function momEventName(eventName: string): string {
+    return `MOM_${eventName.replace(/^MOM_/i, "")}`
+}
+
+function momVariableName(parameterName: string): string {
+    return `mom_${parameterName.replace(/^mom_/i, "")}`
+}
+
+export function createCdlEventHandlerSnippet(handler: CdlEventHandler): string {
+    const globals = [
+        ...new Set(handler.parameterNames.map((parameter) => momVariableName(parameter)))
+    ]
+    const lines = [`proc ${momEventName(handler.eventName)} { } {`]
+
+    if (globals.length > 0) {
+        lines.push(...globals.map((variable) => `    global ${variable}`), "")
+    }
+    lines.push("    #Put your UDE Handler Tcl here", "", "}")
+
+    return lines.join("\n")
+}