import { exhausted } from "../util.ts";
import { File, ModBlockStmt, ModFileStmt, Stmt } from "./ast.ts";

export type VisitRes = "stop" | void;

type R = VisitRes;
type PM = unknown[];

export interface Visitor<
    P extends PM = [],
> {
    visitFile?(file: File, ...p: P): R;
    visitStmt?(stmt: Stmt, ...p: P): R;
    visitErrorStmt?(stmt: Stmt, ...p: P): R;
    visitModBlockStmt?(stmt: Stmt, kind: ModBlockStmt, ...p: P): R;
    visitModFileStmt?(stmt: Stmt, kind: ModFileStmt, ...p: P): R;
}

export function visitFile<
    P extends PM = [],
>(
    v: Visitor<P>,
    file: File,
    ...p: P
) {
    if (v.visitFile?.(file, ...p) === "stop") return;
    visitStmts(v, file.stmts, ...p);
}

export function visitStmts<
    P extends PM = [],
>(
    v: Visitor<P>,
    stmts: Stmt[],
    ...p: P
) {
    for (const stmt of stmts) {
        visitStmt(v, stmt, ...p);
    }
}

export function visitStmt<
    P extends PM = [],
>(
    v: Visitor<P>,
    stmt: Stmt,
    ...p: P
) {
    switch (stmt.kind.tag) {
        case "error":
            if (v.visitErrorStmt?.(stmt, ...p) === "stop") return;
            return;
        case "mod_block":
            if (v.visitModBlockStmt?.(stmt, stmt.kind, ...p) === "stop") return;
            visitStmts(v, stmt.kind.stmts, ...p);
            return;
        case "mod_file":
            if (v.visitModFileStmt?.(stmt, stmt.kind, ...p) === "stop") return;
            return;
    }
    exhausted(stmt.kind);
}