package commonclient

import (
	"context"
	"fmt"
	"strings"

	"github.com/nspcc-dev/neo-go/pkg/core/state"
	"github.com/nspcc-dev/neo-go/pkg/rpcclient/waiter"
	"github.com/nspcc-dev/neo-go/pkg/util"
	"github.com/nspcc-dev/neo-go/pkg/vm/vmstate"
)

const alreadyExistsError = "already exists"

type WaiterOptions struct {
	// IgnoreAlreadyExistsError controls behavior for "already exists" error:
	// - If set to true, it indicates that "already exists" error is not a problem, we should
	//   wait for transaction as usual (this is the behavior of neo-go [waiter.PollingBased]).
	// - If set to false, it indicates that "already exists" should be reported as an error.
	IgnoreAlreadyExistsError bool

	// VerifyExecResults controls whether waiter should ensure that transaction successfully
	// enters blockchain block.
	VerifyExecResults bool
}

// Waiter is a decorator on top of the standard [waiter.Waiter].
// It provides additional behavior (controlled by [WaiterOptions]) on top of the standard
// functionality of awaiting transactions.
type Waiter struct {
	waiter  waiter.Waiter
	options WaiterOptions
}

var _ waiter.Waiter = (*Waiter)(nil)

// NewWaiter decorates the specified waiter in a new [Waiter] instance.
func NewWaiter(waiter waiter.Waiter, options WaiterOptions) *Waiter {
	return &Waiter{
		waiter:  waiter,
		options: options,
	}
}

// Wait allows to wait until transaction will be accepted to the chain.
func (w *Waiter) Wait(h util.Uint256, vub uint32, err error) (*state.AppExecResult, error) {
	if !w.options.IgnoreAlreadyExistsError && errIsAlreadyExists(err) {
		return nil, err
	}
	result, err := w.waiter.Wait(h, vub, err)
	return w.examineExecResult(result, err)
}

// WaitAny waits until at least one of the specified transactions will be accepted
// to the chain.
func (w *Waiter) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uint256) (*state.AppExecResult, error) {
	result, err := w.waiter.WaitAny(ctx, vub, hashes...)
	return w.examineExecResult(result, err)
}

func (w *Waiter) examineExecResult(result *state.AppExecResult, err error) (*state.AppExecResult, error) {
	if !w.options.VerifyExecResults || err != nil {
		return result, err
	}

	if result.Execution.VMState != vmstate.Fault {
		// Transaction didn't fail, so we just return result "as is"
		return result, nil
	}

	// Transaction failed, we extract VM exception from it and report as an error
	if result.FaultException != "" {
		return result, fmt.Errorf("%s", result.FaultException)
	}
	return result, fmt.Errorf("transaction failed, stack=%v", result.Stack)
}

func errIsAlreadyExists(err error) bool {
	if err == nil {
		return false
	}
	return strings.Contains(strings.ToLower(err.Error()), alreadyExistsError)
}