package tool

// applyDefaults fills absent properties with their schema "default", recursing
// into objects and arrays so nested defaults are honoured too.
func applyDefaults(schema map[string]any, args map[string]any) {
	props, _ := schema["properties"].(map[string]any)
	for name, raw := range props {
		ps, ok := raw.(map[string]any)
		if !ok {
			continue
		}
		if rawDefault, has := ps["default"]; has {
			if _, present := args[name]; !present {
				args[name] = deepCopy(rawDefault)
			}
		}
		if val, present := args[name]; present {
			applyDefaultsToValue(ps, val)
		}
	}
}

// applyDefaultsToValue recurses into a present argument value to fill nested
// defaults according to the sub-schema.
func applyDefaultsToValue(schema map[string]any, val any) {
	switch v := val.(type) {
	case map[string]any:
		applyDefaults(schema, v)
	case []any:
		applyDefaultsToArray(schema, v)
	}
}

// applyDefaultsToArray fills defaults for array items, handling the schematic,
// tuple-in-items and 2020-12 prefixItems forms.
func applyDefaultsToArray(schema map[string]any, v []any) {
	switch items := schema["items"].(type) {
	case map[string]any:
		for _, item := range v {
			applyDefaultsToValue(items, item)
		}
	case []any:
		for i, item := range v {
			if i < len(items) {
				if is, ok := items[i].(map[string]any); ok {
					applyDefaultsToValue(is, item)
				}
			}
		}
	}
	if prefix, ok := schema["prefixItems"].([]any); ok {
		for i, item := range v {
			if i < len(prefix) {
				if is, ok := prefix[i].(map[string]any); ok {
					applyDefaultsToValue(is, item)
				}
			}
		}
	}
}

// deepCopy returns a structurally independent copy of a JSON value so defaults
// taken from a compiled schema are not corrupted by later in-place coercion.
func deepCopy(v any) any {
	switch vv := v.(type) {
	case map[string]any:
		out := make(map[string]any, len(vv))
		for k, val := range vv {
			out[k] = deepCopy(val)
		}
		return out
	case []any:
		out := make([]any, len(vv))
		for i, item := range vv {
			out[i] = deepCopy(item)
		}
		return out
	default:
		return vv
	}
}