// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.

package common

import (
	"github.com/ava-labs/gecko/database"
	"github.com/ava-labs/gecko/snow"
)

// VM describes the interface that all consensus VMs must implement
type VM interface {
	// Initialize this VM.
	// [ctx]: Metadata about this VM.
	//     [ctx.networkID]: The ID of the network this VM's chain is running
	//                      on.
	//     [ctx.chainID]: The unique ID of the chain this VM is running on.
	//     [ctx.Log]: Used to log messages
	//     [ctx.NodeID]: The unique staker ID of this node.
	//     [ctx.Lock]: A Read/Write lock shared by this VM and the consensus
	//                 engine that manages this VM. The write lock is held
	//                 whenever code in the consensus engine calls the VM.
	// [db]: The database this VM will persist data to.
	// [genesisBytes]: The byte-encoding of the genesis information of this
	//                 VM. The VM uses it to initialize its state. For
	//                 example, if this VM were an account-based payments
	//                 system, `genesisBytes` would probably contain a genesis
	//                 transaction that gives coins to some accounts, and this
	//                 transaction would be in the genesis block.
	// [toEngine]: The channel used to send messages to the consensus engine.
	// [fxs]: Feature extensions that attach to this VM.
	Initialize(
		ctx *snow.Context,
		db database.Database,
		genesisBytes []byte,
		toEngine chan<- Message,
		fxs []*Fx,
	) error

	// Shutdown is called when the node is shutting down.
	Shutdown()

	// Creates the HTTP handlers for custom chain network calls.
	//
	// This exposes handlers that the outside world can use to communicate with
	// the chain. Each handler has the path:
	// [Address of node]/ext/bc/[chain ID]/[extension]
	//
	// Returns a mapping from [extension]s to HTTP handlers.
	//
	// Each extension can specify how locking is managed for convenience.
	//
	// For example, if this VM implements an account-based payments system,
	// it have an extension called `accounts`, where clients could get
	// information about their accounts.
	CreateHandlers() map[string]*HTTPHandler
}

// StaticVM describes the functionality that allows a user to interact with a VM
// statically.
type StaticVM interface {
	// Creates the HTTP handlers for custom VM network calls.
	//
	// This exposes handlers that the outside world can use to communicate with
	// a static reference to the VM. Each handler has the path:
	// [Address of node]/ext/VM/[VM ID]/[extension]
	//
	// Returns a mapping from [extension]s to HTTP handlers.
	//
	// Each extension can specify how locking is managed for convenience.
	//
	// For example, it might make sense to have an extension for creating
	// genesis bytes this VM can interpret.
	CreateStaticHandlers() map[string]*HTTPHandler
}