package indexer

import (
	"context"

	"cosmossdk.io/schema/addressutil"
	"cosmossdk.io/schema/appdata"
	"cosmossdk.io/schema/logutil"
	"cosmossdk.io/schema/view"
)

// Initializer describes an indexer initialization function and other metadata.
type Initializer struct {
	// InitFunc is the function that initializes the indexer.
	InitFunc InitFunc

	// ConfigType is the type of the configuration object that the indexer expects.
	ConfigType interface{}
}

type InitFunc = func(InitParams) (InitResult, error)

// InitParams is the input to the indexer initialization function.
type InitParams struct {
	// Config is the indexer config.
	Config Config

	// Context is the context that the indexer should use to listen for a shutdown signal via Context.Done(). Other
	// parameters may also be passed through context from the app if necessary. It is expected to be non-nil.
	Context context.Context

	// Logger is a logger the indexer can use to write log messages. It may be nil if the indexer does not need
	// to write logs.
	Logger logutil.Logger

	// AddressCodec is the address codec that the indexer can use to encode and decode addresses. It is
	// expected to be non-nil.
	AddressCodec addressutil.AddressCodec
}

// InitResult is the indexer initialization result and includes the indexer's listener implementation.
type InitResult struct {
	// Listener is the indexer's app data listener.
	Listener appdata.Listener

	// View is a view of indexed data that indexers can provide. It is optional and may be nil.
	// If it is provided it can be used for automated testing and other purposes.
	// At indexer start-up, the block number returned by the view will be used to determine the
	// starting block for the indexer. If the block number is 0, the indexer manager will attempt
	// to perform a catch-up sync of state. Historical events will not be replayed, but an accurate
	// representation of the current state at the height at which indexing began can be reproduced.
	// If the block number is non-zero but does not match the current chain height, a runtime error
	// will occur because this is an unsafe condition that indicates lost data.
	View view.AppData
}