package core

import (
	"context"
	"fmt"

	"github.com/pkg/errors"

	tmpubsub "github.com/tendermint/tendermint/libs/pubsub"
	tmquery "github.com/tendermint/tendermint/libs/pubsub/query"
	ctypes "github.com/tendermint/tendermint/rpc/core/types"
	rpctypes "github.com/tendermint/tendermint/rpc/lib/types"
)

// Subscribe for events via WebSocket.
//
// To tell which events you want, you need to provide a query. query is a
// string, which has a form: "condition AND condition ..." (no OR at the
// moment). condition has a form: "key operation operand". key is a string with
// a restricted set of possible symbols ( \t\n\r\\()"'=>< are not allowed).
// operation can be "=", "<", "<=", ">", ">=", "CONTAINS". operand can be a
// string (escaped with single quotes), number, date or time.
//
// Examples:
//		tm.event = 'NewBlock'               # new blocks
//		tm.event = 'CompleteProposal'       # node got a complete proposal
//		tm.event = 'Tx' AND tx.hash = 'XYZ' # single transaction
//		tm.event = 'Tx' AND tx.height = 5   # all txs of the fifth block
//		tx.height = 5                       # all txs of the fifth block
//
// Tendermint provides a few predefined keys: tm.event, tx.hash and tx.height.
// Note for transactions, you can define additional keys by providing events with
// DeliverTx response.
//
//  import (
//	  abci "github.com/tendermint/tendermint/abci/types"
// 	  "github.com/tendermint/tendermint/libs/pubsub/query"
//  )
//
//  abci.ResponseDeliverTx{
// 	Events: []abci.Event{
// 		{
// 			Type: "rewards.withdraw",
// 			Attributes: cmn.KVPairs{
// 				cmn.KVPair{Key: []byte("address"), Value: []byte("AddrA")},
// 				cmn.KVPair{Key: []byte("source"), Value: []byte("SrcX")},
// 				cmn.KVPair{Key: []byte("amount"), Value: []byte("...")},
// 				cmn.KVPair{Key: []byte("balance"), Value: []byte("...")},
// 			},
// 		},
// 		{
// 			Type: "rewards.withdraw",
// 			Attributes: cmn.KVPairs{
// 				cmn.KVPair{Key: []byte("address"), Value: []byte("AddrB")},
// 				cmn.KVPair{Key: []byte("source"), Value: []byte("SrcY")},
// 				cmn.KVPair{Key: []byte("amount"), Value: []byte("...")},
// 				cmn.KVPair{Key: []byte("balance"), Value: []byte("...")},
// 			},
// 		},
// 		{
// 			Type: "transfer",
// 			Attributes: cmn.KVPairs{
// 				cmn.KVPair{Key: []byte("sender"), Value: []byte("AddrC")},
// 				cmn.KVPair{Key: []byte("recipient"), Value: []byte("AddrD")},
// 				cmn.KVPair{Key: []byte("amount"), Value: []byte("...")},
// 			},
// 		},
// 	},
//  }
//
// All events are indexed by a composite key of the form {eventType}.{evenAttrKey}.
// In the above examples, the following keys would be indexed:
//     - rewards.withdraw.address
//     - rewards.withdraw.source
//     - rewards.withdraw.amount
//     - rewards.withdraw.balance
//     - transfer.sender
//     - transfer.recipient
//     - transfer.amount
//
// Multiple event types with duplicate keys are allowed and are meant to
// categorize unique and distinct events. In the above example, all events
// indexed under the key `rewards.withdraw.address` will have the following
// values stored and queryable:
//
//     - AddrA
//     - AddrB
//
// To create a query for txs where address AddrA withdrew rewards:
//  query.MustParse("tm.event = 'Tx' AND rewards.withdraw.address = 'AddrA'")
//
// To create a query for txs where address AddrA withdrew rewards from source Y:
//  query.MustParse("tm.event = 'Tx' AND rewards.withdraw.address = 'AddrA' AND rewards.withdraw.source = 'Y'")
//
// To create a query for txs where AddrA transferred funds:
//  query.MustParse("tm.event = 'Tx' AND transfer.sender = 'AddrA'")
//
// The following queries would return no results:
//  query.MustParse("tm.event = 'Tx' AND transfer.sender = 'AddrZ'")
//  query.MustParse("tm.event = 'Tx' AND rewards.withdraw.address = 'AddrZ'")
//  query.MustParse("tm.event = 'Tx' AND rewards.withdraw.source = 'W'")
//
// See list of all possible events here
// https://godoc.org/github.com/tendermint/tendermint/types#pkg-constants
//
// For complete query syntax, check out
// https://godoc.org/github.com/tendermint/tendermint/libs/pubsub/query.
//
// ```go
// import "github.com/tendermint/tendermint/types"
//
// client := client.NewHTTP("tcp://0.0.0.0:26657", "/websocket")
// err := client.Start()
// if err != nil {
//   // handle error
// }
// defer client.Stop()
// ctx, cancel := context.WithTimeout(context.Background(), 1 * time.Second)
// defer cancel()
// query := "tm.event = 'Tx' AND tx.height = 3"
// txs, err := client.Subscribe(ctx, "test-client", query)
// if err != nil {
//   // handle error
// }
//
// go func() {
//   for e := range txs {
//     fmt.Println("got ", e.Data.(types.EventDataTx))
//	 }
// }()
// ```
//
// > The above command returns JSON structured like this:
//
// ```json
// {
// 	"error": "",
// 	"result": {},
// 	"id": "",
// 	"jsonrpc": "2.0"
// }
// ```
//
// ### Query Parameters
//
// | Parameter | Type   | Default | Required | Description |
// |-----------+--------+---------+----------+-------------|
// | query     | string | ""      | true     | Query       |
//
// <aside class="notice">WebSocket only</aside>
func Subscribe(ctx *rpctypes.Context, query string) (*ctypes.ResultSubscribe, error) {
	addr := ctx.RemoteAddr()

	if eventBus.NumClients() >= config.MaxSubscriptionClients {
		return nil, fmt.Errorf("max_subscription_clients %d reached", config.MaxSubscriptionClients)
	} else if eventBus.NumClientSubscriptions(addr) >= config.MaxSubscriptionsPerClient {
		return nil, fmt.Errorf("max_subscriptions_per_client %d reached", config.MaxSubscriptionsPerClient)
	}

	logger.Info("Subscribe to query", "remote", addr, "query", query)

	q, err := tmquery.New(query)
	if err != nil {
		return nil, errors.Wrap(err, "failed to parse query")
	}

	subCtx, cancel := context.WithTimeout(ctx.Context(), SubscribeTimeout)
	defer cancel()

	sub, err := eventBus.Subscribe(subCtx, addr, q)
	if err != nil {
		return nil, err
	}

	go func() {
		for {
			select {
			case msg := <-sub.Out():
				resultEvent := &ctypes.ResultEvent{Query: query, Data: msg.Data(), Events: msg.Events()}
				ctx.WSConn.TryWriteRPCResponse(
					rpctypes.NewRPCSuccessResponse(
						ctx.WSConn.Codec(),
						rpctypes.JSONRPCStringID(fmt.Sprintf("%v#event", ctx.JSONReq.ID)),
						resultEvent,
					))
			case <-sub.Cancelled():
				if sub.Err() != tmpubsub.ErrUnsubscribed {
					var reason string
					if sub.Err() == nil {
						reason = "Tendermint exited"
					} else {
						reason = sub.Err().Error()
					}
					ctx.WSConn.TryWriteRPCResponse(
						rpctypes.RPCServerError(rpctypes.JSONRPCStringID(
							fmt.Sprintf("%v#event", ctx.JSONReq.ID)),
							fmt.Errorf("subscription was cancelled (reason: %s)", reason),
						))
				}
				return
			}
		}
	}()

	return &ctypes.ResultSubscribe{}, nil
}

// Unsubscribe from events via WebSocket.
//
// ```go
// client := client.NewHTTP("tcp://0.0.0.0:26657", "/websocket")
// err := client.Start()
// if err != nil {
//   // handle error
// }
// defer client.Stop()
// query := "tm.event = 'Tx' AND tx.height = 3"
// err = client.Unsubscribe(context.Background(), "test-client", query)
// if err != nil {
//   // handle error
// }
// ```
//
// > The above command returns JSON structured like this:
//
// ```json
// {
// 	"error": "",
// 	"result": {},
// 	"id": "",
// 	"jsonrpc": "2.0"
// }
// ```
//
// ### Query Parameters
//
// | Parameter | Type   | Default | Required | Description |
// |-----------+--------+---------+----------+-------------|
// | query     | string | ""      | true     | Query       |
//
// <aside class="notice">WebSocket only</aside>
func Unsubscribe(ctx *rpctypes.Context, query string) (*ctypes.ResultUnsubscribe, error) {
	addr := ctx.RemoteAddr()
	logger.Info("Unsubscribe from query", "remote", addr, "query", query)
	q, err := tmquery.New(query)
	if err != nil {
		return nil, errors.Wrap(err, "failed to parse query")
	}
	err = eventBus.Unsubscribe(context.Background(), addr, q)
	if err != nil {
		return nil, err
	}
	return &ctypes.ResultUnsubscribe{}, nil
}

// Unsubscribe from all events via WebSocket.
//
// ```go
// client := client.NewHTTP("tcp://0.0.0.0:26657", "/websocket")
// err := client.Start()
// if err != nil {
//   // handle error
// }
// defer client.Stop()
// err = client.UnsubscribeAll(context.Background(), "test-client")
// if err != nil {
//   // handle error
// }
// ```
//
// > The above command returns JSON structured like this:
//
// ```json
// {
// 	"error": "",
// 	"result": {},
// 	"id": "",
// 	"jsonrpc": "2.0"
// }
// ```
//
// <aside class="notice">WebSocket only</aside>
func UnsubscribeAll(ctx *rpctypes.Context) (*ctypes.ResultUnsubscribe, error) {
	addr := ctx.RemoteAddr()
	logger.Info("Unsubscribe from all", "remote", addr)
	err := eventBus.UnsubscribeAll(context.Background(), addr)
	if err != nil {
		return nil, err
	}
	return &ctypes.ResultUnsubscribe{}, nil
}