module walker

import v.ast

// Visitor defines a visit method which is invoked by the walker in each node it encounters.
pub interface Visitor {
mut:
    visit(node &ast.Node) !
}

pub type InspectorFn = fn (node &ast.Node, data voidptr) bool

fn empty_callback(node &ast.Node, data voidptr) bool {
    panic('empty ast.walker, node: ${voidptr(node)}, data: ${voidptr(data)}')
}

struct Inspector {
    inspector_callback InspectorFn = empty_callback
mut:
    data voidptr
}

pub fn (i &Inspector) visit(node &ast.Node) ! {
    if i.inspector_callback(node, i.data) {
        return
    }
    return error('')
}

// inspect traverses and checks the AST node on a depth-first order and based on the data given
pub fn inspect(node &ast.Node, data voidptr, inspector_callback InspectorFn) {
    mut inspector := Inspector{inspector_callback, data}
    walk(mut inspector, node)
}

// walk traverses the AST using the given visitor
pub fn walk(mut visitor Visitor, node &ast.Node) {
    visitor.visit(node) or { return }
    children := node.children()
    for child_node in children {
        walk(mut visitor, &child_node)
    }
}