chore: initial commit

utils/command_completion.ts

@@ -0,0 +1,63 @@
+interface CommandNode {
+    flags?: {command_node_type?: number};
+    children?: number[];
+    redirectNode?: number;
+    extraNodeData?: {name?: string; parser?: string; properties?: {type?: number | string}};
+}
+interface CommandTree {nodes: CommandNode[]; rootIndex: number}
+const trees = new WeakMap<object, CommandTree>();
+
+export function remember_command_tree(instance: object, packet: unknown): void {
+    const tree = packet as CommandTree;
+    if (tree && Array.isArray(tree.nodes) && Number.isSafeInteger(tree.rootIndex)
+        && tree.nodes.length <= 100_000 && tree.nodes[tree.rootIndex]) trees.set(instance, tree);
+}
+
+export function local_command_completion(instance: object, input: string, players: string[]): {matches: string[]; start: number; length: number} {
+    const start = input.search(/\S*$/);
+    const offset = start === 0 && input.startsWith('/') ? 1 : start;
+    const result = {matches: [] as string[], start: offset, length: input.length - offset};
+    const tree = trees.get(instance);
+    if (!tree || !input.startsWith('/')) return result;
+    // Walk complete arguments; only the final (possibly empty) token is being completed.
+    const tokens = input.slice(1, start || 1).trim().split(/\s+/).filter(Boolean);
+    let parents = [tree.rootIndex];
+    const children = (index: number): number[] => {
+        const node = tree.nodes[index];
+        const redirect = node?.redirectNode;
+        return Number.isSafeInteger(redirect) ? tree.nodes[redirect!]?.children ?? [] : node?.children ?? [];
+    };
+    for (const token of tokens) {
+        const next: number[] = [];
+        for (const parent of parents) {
+            for (const index of children(parent)) {
+                const node = tree.nodes[index];
+                if (node?.flags?.command_node_type === 1 && node.extraNodeData?.name === token) next.push(index);
+                else if (node?.flags?.command_node_type === 2) {
+                    const parser = node.extraNodeData?.parser;
+                    const kind = node.extraNodeData?.properties?.type;
+                    // Quoted and greedy strings need Brigadier parsing; leave their suggestions to the server.
+                    if (token.includes('"') || parser === 'minecraft:message' || parser === 'brigadier:string' && (kind === 2 || kind === 'greedy_phrase')) continue;
+                    next.push(index);
+                }
+            }
+        }
+        parents = [...new Set(next)].slice(0, 256);
+    }
+    const prefix = input.slice(offset).toLowerCase();
+    for (const parent of parents) {
+        for (const index of children(parent)) {
+            const node = tree.nodes[index];
+            const data = node?.extraNodeData;
+            const suggestions = node?.flags?.command_node_type === 1 ? [data?.name]
+                : data?.parser === 'brigadier:bool' ? ['true', 'false']
+                    : data?.parser === 'minecraft:entity' || data?.parser === 'minecraft:game_profile' ? players : [];
+            for (const match of suggestions) {
+                if (typeof match === 'string' && match.length && match.length <= 256
+                    && match.toLowerCase().startsWith(prefix) && !result.matches.includes(match)) result.matches.push(match);
+                if (result.matches.length >= 100) return result;
+            }
+        }
+    }
+    return result;
+}