module walker

import toml.ast

// Visitor defines a visit method which is invoked by the walker on each Value node it encounters.
pub interface Visitor {
    visit(value &ast.Value) !
}

// Modifier defines a modify method which is invoked by the walker on each Value node it encounters.
pub interface Modifier {
    modify(mut value ast.Value) !
}

pub type InspectorFn = fn (value &ast.Value, data voidptr) !

struct Inspector {
    inspector_callback InspectorFn = unsafe { nil }
mut:
    data voidptr
}

// visit calls the inspector callback on the specified Value node.
pub fn (i &Inspector) visit(value &ast.Value) ! {
    i.inspector_callback(value, i.data) or { return err }
}

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

// walk traverses the AST using the given visitor
@[autofree_bug; manualfree]
pub fn walk(visitor Visitor, value &ast.Value) ! {
    if value is map[string]ast.Value {
        value_map := value as map[string]ast.Value
        for _, val in value_map {
            walk(visitor, &val)!
        }
    }
    if value is []ast.Value {
        value_array := value as []ast.Value
        for val in value_array {
            walk(visitor, &val)!
        }
    } else {
        visitor.visit(value)!
    }
}

// walk_and_modify traverses the AST using the given modifier and lets the visitor
// modify the contents.
@[autofree_bug; manualfree]
pub fn walk_and_modify(modifier Modifier, mut value ast.Value) ! {
    if value is map[string]ast.Value {
        mut value_map := value as map[string]ast.Value
        for _, mut val in value_map {
            walk_and_modify(modifier, mut &val)!
        }
    }
    if value is []ast.Value {
        mut value_array := value as []ast.Value
        for mut val in value_array {
            walk_and_modify(modifier, mut &val)!
        }
    } else {
        modifier.modify(mut value)!
    }
}