interfaces

type Evaluator interface {
	// Fetch populates the values map being passed into it by translating input expressions into a series of
	// parser.MetricRequest and fetching the raw data from the configured backend.
	//
	// It returns a map of only the data requested in the current invocation, scaled to a common step.
	Fetch(ctx context.Context, e []parser.Expr, from, until int64, values map[parser.MetricRequest][]*types.MetricData) (map[parser.MetricRequest][]*types.MetricData, error)
	// Eval uses the raw data within the values map being passed into it to in order to evaluate the input expression.
	Eval(ctx context.Context, e parser.Expr, from, until int64, values map[parser.MetricRequest][]*types.MetricData) ([]*types.MetricData, error)
}

type Function interface {
	Do(ctx context.Context, evaluator Evaluator, e parser.Expr, from, until int64, values map[parser.MetricRequest][]*types.MetricData) ([]*types.MetricData, error)
	Description() map[string]types.FunctionDescription
}

type FunctionMetadata struct {
	Name     string
	Filename string
	Order    Order
	F        Function
}

type Order int

type RewriteFunction interface {
	Do(ctx context.Context, evaluator Evaluator, e parser.Expr, from, until int64, values map[parser.MetricRequest][]*types.MetricData) (bool, []string, error)
	Description() map[string]types.FunctionDescription
}

type RewriteFunctionMetadata struct {
	Name     string
	Filename string
	Order    Order
	F        RewriteFunction
}