package gax

import (
	"time"

	"google.golang.org/grpc/codes"
)

type CallOption interface {
	Resolve(*CallSettings)
}

type callOptions []CallOption

func (opts callOptions) Resolve(s *CallSettings) *CallSettings {
	for _, opt := range opts {
		opt.Resolve(s)
	}
	return s
}

// Encapsulates the call settings for a particular API call.
type CallSettings struct {
	Timeout       time.Duration
	RetrySettings RetrySettings
}

// Per-call configurable settings for retrying upon transient failure.
type RetrySettings struct {
	RetryCodes      map[codes.Code]bool
	BackoffSettings BackoffSettings
}

// Parameters to the exponential backoff algorithm for retrying.
type BackoffSettings struct {
	DelayTimeoutSettings MultipliableDuration
	RPCTimeoutSettings   MultipliableDuration
	TotalTimeout         time.Duration
}

type MultipliableDuration struct {
	Initial    time.Duration
	Max        time.Duration
	Multiplier float64
}

func (w CallSettings) Resolve(s *CallSettings) {
	s.Timeout = w.Timeout
	s.RetrySettings = w.RetrySettings

	s.RetrySettings.RetryCodes = make(map[codes.Code]bool, len(w.RetrySettings.RetryCodes))
	for key, value := range w.RetrySettings.RetryCodes {
		s.RetrySettings.RetryCodes[key] = value
	}
}

type withTimeout time.Duration

func (w withTimeout) Resolve(s *CallSettings) {
	s.Timeout = time.Duration(w)
}

// WithTimeout sets the client-side timeout for API calls if the call isn't
// retrying.
func WithTimeout(timeout time.Duration) CallOption {
	return withTimeout(timeout)
}

type withRetryCodes []codes.Code

func (w withRetryCodes) Resolve(s *CallSettings) {
	s.RetrySettings.RetryCodes = make(map[codes.Code]bool)
	for _, code := range []codes.Code(w) {
		s.RetrySettings.RetryCodes[code] = true
	}
}

// WithRetryCodes sets a list of Google API canonical error codes upon which a
// retry should be attempted. If nil, the call will not retry.
func WithRetryCodes(retryCodes []codes.Code) CallOption {
	return withRetryCodes(retryCodes)
}

type withDelayTimeoutSettings MultipliableDuration

func (w withDelayTimeoutSettings) Resolve(s *CallSettings) {
	s.RetrySettings.BackoffSettings.DelayTimeoutSettings = MultipliableDuration(w)
}

// WithDelayTimeoutSettings specifies:
// - The initial delay time, in milliseconds, between the completion of
//   the first failed request and the initiation of the first retrying
//   request.
// - The multiplier by which to increase the delay time between the
//   completion of failed requests, and the initiation of the subsequent
//   retrying request.
// - The maximum delay time, in milliseconds, between requests. When this
//   value is reached, `RetryDelayMultiplier` will no longer be used to
//   increase delay time.
func WithDelayTimeoutSettings(initial time.Duration, max time.Duration, multiplier float64) CallOption {
	return withDelayTimeoutSettings(MultipliableDuration{initial, max, multiplier})
}

type withRPCTimeoutSettings MultipliableDuration

func (w withRPCTimeoutSettings) Resolve(s *CallSettings) {
	s.RetrySettings.BackoffSettings.RPCTimeoutSettings = MultipliableDuration(w)
}

// WithRPCTimeoutSettings specifies:
// - The initial timeout parameter to the request.
// - The multiplier by which to increase the timeout parameter between
//   failed requests.
// - The maximum timeout parameter, in milliseconds, for a request. When
//   this value is reached, `RPCTimeoutMultiplier` will no longer be used
//   to increase the timeout.
func WithRPCTimeoutSettings(initial time.Duration, max time.Duration, multiplier float64) CallOption {
	return withRPCTimeoutSettings(MultipliableDuration{initial, max, multiplier})
}

type withTotalRetryTimeout time.Duration

func (w withTotalRetryTimeout) Resolve(s *CallSettings) {
	s.RetrySettings.BackoffSettings.TotalTimeout = time.Duration(w)
}

// WithTotalRetryTimeout sets the total time, in milliseconds, starting from
// when the initial request is sent, after which an error will be returned
// regardless of the retrying attempts made meanwhile.
func WithTotalRetryTimeout(totalRetryTimeout time.Duration) CallOption {
	return withTotalRetryTimeout(totalRetryTimeout)
}