fix: retry caldav init at startup

vendor/github.com/avast/retry-go/options.go

@@ -0,0 +1,193 @@
+package retry
+
+import (
+	"context"
+	"math"
+	"math/rand"
+	"time"
+)
+
+// Function signature of retry if function
+type RetryIfFunc func(error) bool
+
+// Function signature of OnRetry function
+// n = count of attempts
+type OnRetryFunc func(n uint, err error)
+
+type DelayTypeFunc func(n uint, config *Config) time.Duration
+
+type Config struct {
+	attempts      uint
+	delay         time.Duration
+	maxDelay      time.Duration
+	maxJitter     time.Duration
+	onRetry       OnRetryFunc
+	retryIf       RetryIfFunc
+	delayType     DelayTypeFunc
+	lastErrorOnly bool
+	context       context.Context
+
+	maxBackOffN uint
+}
+
+// Option represents an option for retry.
+type Option func(*Config)
+
+// return the direct last error that came from the retried function
+// default is false (return wrapped errors with everything)
+func LastErrorOnly(lastErrorOnly bool) Option {
+	return func(c *Config) {
+		c.lastErrorOnly = lastErrorOnly
+	}
+}
+
+// Attempts set count of retry
+// default is 10
+func Attempts(attempts uint) Option {
+	return func(c *Config) {
+		c.attempts = attempts
+	}
+}
+
+// Delay set delay between retry
+// default is 100ms
+func Delay(delay time.Duration) Option {
+	return func(c *Config) {
+		c.delay = delay
+	}
+}
+
+// MaxDelay set maximum delay between retry
+// does not apply by default
+func MaxDelay(maxDelay time.Duration) Option {
+	return func(c *Config) {
+		c.maxDelay = maxDelay
+	}
+}
+
+// MaxJitter sets the maximum random Jitter between retries for RandomDelay
+func MaxJitter(maxJitter time.Duration) Option {
+	return func(c *Config) {
+		c.maxJitter = maxJitter
+	}
+}
+
+// DelayType set type of the delay between retries
+// default is BackOff
+func DelayType(delayType DelayTypeFunc) Option {
+	return func(c *Config) {
+		c.delayType = delayType
+	}
+}
+
+// BackOffDelay is a DelayType which increases delay between consecutive retries
+func BackOffDelay(n uint, config *Config) time.Duration {
+	// 1 << 63 would overflow signed int64 (time.Duration), thus 62.
+	const max uint = 62
+
+	if config.maxBackOffN == 0 {
+		if config.delay <= 0 {
+			config.delay = 1
+		}
+		config.maxBackOffN = max - uint(math.Floor(math.Log2(float64(config.delay))))
+	}
+
+	if n > config.maxBackOffN {
+		n = config.maxBackOffN
+	}
+	return config.delay << n
+}
+
+// FixedDelay is a DelayType which keeps delay the same through all iterations
+func FixedDelay(_ uint, config *Config) time.Duration {
+	return config.delay
+}
+
+// RandomDelay is a DelayType which picks a random delay up to config.maxJitter
+func RandomDelay(_ uint, config *Config) time.Duration {
+	return time.Duration(rand.Int63n(int64(config.maxJitter)))
+}
+
+// CombineDelay is a DelayType the combines all of the specified delays into a new DelayTypeFunc
+func CombineDelay(delays ...DelayTypeFunc) DelayTypeFunc {
+	const maxInt64 = uint64(math.MaxInt64)
+
+	return func(n uint, config *Config) time.Duration {
+		var total uint64
+		for _, delay := range delays {
+			total += uint64(delay(n, config))
+			if total > maxInt64 {
+				total = maxInt64
+			}
+		}
+		return time.Duration(total)
+	}
+}
+
+// OnRetry function callback are called each retry
+//
+// log each retry example:
+//
+//	retry.Do(
+//		func() error {
+//			return errors.New("some error")
+//		},
+//		retry.OnRetry(func(n uint, err error) {
+//			log.Printf("#%d: %s\n", n, err)
+//		}),
+//	)
+func OnRetry(onRetry OnRetryFunc) Option {
+	return func(c *Config) {
+		c.onRetry = onRetry
+	}
+}
+
+// RetryIf controls whether a retry should be attempted after an error
+// (assuming there are any retry attempts remaining)
+//
+// skip retry if special error example:
+//
+//	retry.Do(
+//		func() error {
+//			return errors.New("special error")
+//		},
+//		retry.RetryIf(func(err error) bool {
+//			if err.Error() == "special error" {
+//				return false
+//			}
+//			return true
+//		})
+//	)
+//
+// By default RetryIf stops execution if the error is wrapped using `retry.Unrecoverable`,
+// so above example may also be shortened to:
+//
+//	retry.Do(
+//		func() error {
+//			return retry.Unrecoverable(errors.New("special error"))
+//		}
+//	)
+func RetryIf(retryIf RetryIfFunc) Option {
+	return func(c *Config) {
+		c.retryIf = retryIf
+	}
+}
+
+// Context allow to set context of retry
+// default are Background context
+//
+//	example of immediately cancellation (maybe it isn't the best example, but it describes behavior enough; I hope)
+//	ctx, cancel := context.WithCancel(context.Background())
+//	cancel()
+//
+//	retry.Do(
+//		func() error {
+//			...
+//		},
+//		retry.Context(ctx),
+//	)
+func Context(ctx context.Context) Option {
+	return func(c *Config) {
+		c.context = ctx
+	}
+}