/*
Copyright 2018 The Knative Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package gc

import (
	"context"
	"fmt"
	"strconv"
	"strings"
	"time"

	corev1 "k8s.io/api/core/v1"
	cm "knative.dev/pkg/configmap"
	"knative.dev/pkg/controller"
	"knative.dev/pkg/logging"
)

const (
	// ConfigName is the name of the config map for garbage collection.
	ConfigName = "config-gc"

	// Disabled is the value (-1) used by various config map values to indicate
	// the setting is disabled.
	Disabled = -1

	disabled = "disabled"
)

// Config defines the tunable parameters for Garbage Collection.
type Config struct {
	// Delay duration after a revision create before considering it for GC
	StaleRevisionCreateDelay time.Duration
	// Timeout since a revision lastPinned before it should be GC'd
	// This must be longer than the controller resync period
	StaleRevisionTimeout time.Duration
	// Minimum number of generations of revisions to keep before considering for GC.
	StaleRevisionMinimumGenerations int64
	// Minimum staleness duration before updating lastPinned
	StaleRevisionLastpinnedDebounce time.Duration

	// Duration from creation when a Revision should be considered active
	// and exempt from GC. Note that GCMaxStaleRevision may override this if set.
	// Set Disabled (-1) to disable/ignore duration and always consider active.
	RetainSinceCreateTime time.Duration
	// Duration from last active when a Revision should be considered active
	// and exempt from GC.Note that GCMaxStaleRevision may override this if set.
	// Set Disabled (-1) to disable/ignore duration and always consider active.
	RetainSinceLastActiveTime time.Duration
	// Minimum number of non-active revisions to keep before considering for GC.
	MinNonActiveRevisions int64
	// Maximum number of non-active revisions to keep before considering for GC.
	// regardless of creation or staleness time-bounds.
	// Set Disabled (-1) to disable/ignore max.
	MaxNonActiveRevisions int64
}

func defaultConfig() *Config {
	return &Config{
		// V1 GC Settings
		StaleRevisionCreateDelay:        48 * time.Hour,
		StaleRevisionTimeout:            15 * time.Hour,
		StaleRevisionLastpinnedDebounce: 5 * time.Hour,
		StaleRevisionMinimumGenerations: 20,

		// V2 GC Settings
		RetainSinceCreateTime:     48 * time.Hour,
		RetainSinceLastActiveTime: 15 * time.Hour,
		MinNonActiveRevisions:     20,
		MaxNonActiveRevisions:     1000,
	}
}

// NewConfigFromConfigMapFunc creates a Config from the supplied ConfigMap func.
func NewConfigFromConfigMapFunc(ctx context.Context) func(configMap *corev1.ConfigMap) (*Config, error) {
	logger := logging.FromContext(ctx)
	minRevisionTimeout := controller.GetResyncPeriod(ctx)
	return func(configMap *corev1.ConfigMap) (*Config, error) {
		c := defaultConfig()

		var retainCreate, retainActive, max string
		if err := cm.Parse(configMap.Data,
			cm.AsDuration("stale-revision-create-delay", &c.StaleRevisionCreateDelay),
			cm.AsDuration("stale-revision-timeout", &c.StaleRevisionTimeout),
			cm.AsDuration("stale-revision-lastpinned-debounce", &c.StaleRevisionLastpinnedDebounce),
			cm.AsInt64("stale-revision-minimum-generations", &c.StaleRevisionMinimumGenerations),

			// v2 settings
			cm.AsString("retain-since-create-time", &retainCreate),
			cm.AsString("retain-since-last-active-time", &retainActive),
			cm.AsInt64("min-non-active-revisions", &c.MinNonActiveRevisions),
			cm.AsString("max-non-active-revisions", &max),
		); err != nil {
			return nil, fmt.Errorf("failed to parse data: %w", err)
		}

		if c.StaleRevisionMinimumGenerations < 0 {
			return nil, fmt.Errorf(
				"stale-revision-minimum-generations must be non-negative, was: %d",
				c.StaleRevisionMinimumGenerations)
		}
		if c.StaleRevisionTimeout-c.StaleRevisionLastpinnedDebounce < minRevisionTimeout {
			logger.Warnf("Got revision timeout of %v, minimum supported value is %v",
				c.StaleRevisionTimeout, minRevisionTimeout+c.StaleRevisionLastpinnedDebounce)
			c.StaleRevisionTimeout = minRevisionTimeout + c.StaleRevisionLastpinnedDebounce
		}

		// validate V2 settings
		if err := parseDisabledOrDuration(retainCreate, &c.RetainSinceCreateTime); err != nil {
			return nil, fmt.Errorf("failed to parse retain-since-create-time: %w", err)
		}
		if err := parseDisabledOrDuration(retainActive, &c.RetainSinceLastActiveTime); err != nil {
			return nil, fmt.Errorf("failed to parse retain-since-last-active-time: %w", err)
		}
		if err := parseDisabledOrInt64(max, &c.MaxNonActiveRevisions); err != nil {
			return nil, fmt.Errorf("failed to parse max-stale-revisions: %w", err)
		}
		if c.MinNonActiveRevisions < 0 {
			return nil, fmt.Errorf("min-non-active-revisions must be non-negative, was: %d", c.MinNonActiveRevisions)
		}
		if c.MaxNonActiveRevisions >= 0 && c.MinNonActiveRevisions > c.MaxNonActiveRevisions {
			return nil, fmt.Errorf("min-non-active-revisions(%d) must be <= max-stale-revisions(%d)", c.MinNonActiveRevisions, c.MaxNonActiveRevisions)
		}
		return c, nil
	}
}

func parseDisabledOrInt64(val string, toSet *int64) error {
	switch {
	case val == "":
		// keep default value
	case strings.EqualFold(val, disabled):
		*toSet = Disabled
	default:
		parsed, err := strconv.ParseUint(val, 10, 64)
		if err != nil {
			return err
		}
		*toSet = int64(parsed)
	}
	return nil
}

func parseDisabledOrDuration(val string, toSet *time.Duration) error {
	switch {
	case val == "":
		// keep default value
	case strings.EqualFold(val, disabled):
		*toSet = time.Duration(Disabled)
	default:
		parsed, err := time.ParseDuration(val)
		if err != nil {
			return err
		}
		if parsed < 0 {
			return fmt.Errorf("must be non-negative")
		}
		*toSet = parsed
	}
	return nil
}