// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0

package api

import (
	"bytes"
	"fmt"
	"io"
	"strconv"
	"strings"
	"time"
)

// AutopilotConfiguration is used for querying/setting the Autopilot configuration.
// Autopilot helps manage operator tasks related to Consul servers like removing
// failed servers from the Raft quorum.
type AutopilotConfiguration struct {
	// CleanupDeadServers controls whether to remove dead servers from the Raft
	// peer list when a new server joins
	CleanupDeadServers bool

	// LastContactThreshold is the limit on the amount of time a server can go
	// without leader contact before being considered unhealthy.
	LastContactThreshold *ReadableDuration

	// MaxTrailingLogs is the amount of entries in the Raft Log that a server can
	// be behind before being considered unhealthy.
	MaxTrailingLogs uint64

	// MinQuorum sets the minimum number of servers allowed in a cluster before
	// autopilot can prune dead servers.
	MinQuorum uint

	// ServerStabilizationTime is the minimum amount of time a server must be
	// in a stable, healthy state before it can be added to the cluster. Only
	// applicable with Raft protocol version 3 or higher.
	ServerStabilizationTime *ReadableDuration

	// (Enterprise-only) RedundancyZoneTag is the node tag to use for separating
	// servers into zones for redundancy. If left blank, this feature will be disabled.
	RedundancyZoneTag string

	// (Enterprise-only) DisableUpgradeMigration will disable Autopilot's upgrade migration
	// strategy of waiting until enough newer-versioned servers have been added to the
	// cluster before promoting them to voters.
	DisableUpgradeMigration bool

	// (Enterprise-only) UpgradeVersionTag is the node tag to use for version info when
	// performing upgrade migrations. If left blank, the Consul version will be used.
	UpgradeVersionTag string

	// CreateIndex holds the index corresponding the creation of this configuration.
	// This is a read-only field.
	CreateIndex uint64

	// ModifyIndex will be set to the index of the last update when retrieving the
	// Autopilot configuration. Resubmitting a configuration with
	// AutopilotCASConfiguration will perform a check-and-set operation which ensures
	// there hasn't been a subsequent update since the configuration was retrieved.
	ModifyIndex uint64
}

// Defines default values for the AutopilotConfiguration type, consistent with
// https://www.consul.io/api-docs/operator/autopilot#parameters-1
func NewAutopilotConfiguration() AutopilotConfiguration {
	cfg := AutopilotConfiguration{
		CleanupDeadServers:      true,
		LastContactThreshold:    NewReadableDuration(200 * time.Millisecond),
		MaxTrailingLogs:         250,
		MinQuorum:               0,
		ServerStabilizationTime: NewReadableDuration(10 * time.Second),
		RedundancyZoneTag:       "",
		DisableUpgradeMigration: false,
		UpgradeVersionTag:       "",
	}

	return cfg
}

// ServerHealth is the health (from the leader's point of view) of a server.
type ServerHealth struct {
	// ID is the raft ID of the server.
	ID string

	// Name is the node name of the server.
	Name string

	// Address is the address of the server.
	Address string

	// The status of the SerfHealth check for the server.
	SerfStatus string

	// Version is the Consul version of the server.
	Version string

	// Leader is whether this server is currently the leader.
	Leader bool

	// LastContact is the time since this node's last contact with the leader.
	LastContact *ReadableDuration

	// LastTerm is the highest leader term this server has a record of in its Raft log.
	LastTerm uint64

	// LastIndex is the last log index this server has a record of in its Raft log.
	LastIndex uint64

	// Healthy is whether or not the server is healthy according to the current
	// Autopilot config.
	Healthy bool

	// Voter is whether this is a voting server.
	Voter bool

	// StableSince is the last time this server's Healthy value changed.
	StableSince time.Time
}

// OperatorHealthReply is a representation of the overall health of the cluster
type OperatorHealthReply struct {
	// Healthy is true if all the servers in the cluster are healthy.
	Healthy bool

	// FailureTolerance is the number of healthy servers that could be lost without
	// an outage occurring.
	FailureTolerance int

	// Servers holds the health of each server.
	Servers []ServerHealth
}

type AutopilotState struct {
	Healthy                    bool
	FailureTolerance           int
	OptimisticFailureTolerance int

	Servers         map[string]AutopilotServer
	Leader          string
	Voters          []string
	ReadReplicas    []string                 `json:",omitempty"`
	RedundancyZones map[string]AutopilotZone `json:",omitempty"`
	Upgrade         *AutopilotUpgrade        `json:",omitempty"`
}

type AutopilotServer struct {
	ID             string
	Name           string
	Address        string
	NodeStatus     string
	Version        string
	LastContact    *ReadableDuration
	LastTerm       uint64
	LastIndex      uint64
	Healthy        bool
	StableSince    time.Time
	RedundancyZone string `json:",omitempty"`
	UpgradeVersion string `json:",omitempty"`
	ReadReplica    bool
	Status         AutopilotServerStatus
	Meta           map[string]string
	NodeType       AutopilotServerType
}

type AutopilotServerStatus string

const (
	AutopilotServerNone     AutopilotServerStatus = "none"
	AutopilotServerLeader   AutopilotServerStatus = "leader"
	AutopilotServerVoter    AutopilotServerStatus = "voter"
	AutopilotServerNonVoter AutopilotServerStatus = "non-voter"
	AutopilotServerStaging  AutopilotServerStatus = "staging"
)

type AutopilotServerType string

const (
	AutopilotTypeVoter          AutopilotServerType = "voter"
	AutopilotTypeReadReplica    AutopilotServerType = "read-replica"
	AutopilotTypeZoneVoter      AutopilotServerType = "zone-voter"
	AutopilotTypeZoneExtraVoter AutopilotServerType = "zone-extra-voter"
	AutopilotTypeZoneStandby    AutopilotServerType = "zone-standby"
)

type AutopilotZone struct {
	Servers          []string
	Voters           []string
	FailureTolerance int
}

type AutopilotZoneUpgradeVersions struct {
	TargetVersionVoters    []string `json:",omitempty"`
	TargetVersionNonVoters []string `json:",omitempty"`
	OtherVersionVoters     []string `json:",omitempty"`
	OtherVersionNonVoters  []string `json:",omitempty"`
}

type AutopilotUpgrade struct {
	Status                    AutopilotUpgradeStatus
	TargetVersion             string                                  `json:",omitempty"`
	TargetVersionVoters       []string                                `json:",omitempty"`
	TargetVersionNonVoters    []string                                `json:",omitempty"`
	TargetVersionReadReplicas []string                                `json:",omitempty"`
	OtherVersionVoters        []string                                `json:",omitempty"`
	OtherVersionNonVoters     []string                                `json:",omitempty"`
	OtherVersionReadReplicas  []string                                `json:",omitempty"`
	RedundancyZones           map[string]AutopilotZoneUpgradeVersions `json:",omitempty"`
}

type AutopilotUpgradeStatus string

const (
	// AutopilotUpgradeIdle is the status when no upgrade is in progress.
	AutopilotUpgradeIdle AutopilotUpgradeStatus = "idle"

	// AutopilotUpgradeAwaitNewVoters is the status when more servers of
	// the target version must be added in order to start the promotion
	// phase of the upgrade
	AutopilotUpgradeAwaitNewVoters AutopilotUpgradeStatus = "await-new-voters"

	// AutopilotUpgradePromoting is the status when autopilot is promoting
	// servers of the target version.
	AutopilotUpgradePromoting AutopilotUpgradeStatus = "promoting"

	// AutopilotUpgradeDemoting is the status when autopilot is demoting
	// servers not on the target version
	AutopilotUpgradeDemoting AutopilotUpgradeStatus = "demoting"

	// AutopilotUpgradeLeaderTransfer is the status when autopilot is transferring
	// leadership from a server running an older version to a server
	// using the target version.
	AutopilotUpgradeLeaderTransfer AutopilotUpgradeStatus = "leader-transfer"

	// AutopilotUpgradeAwaitNewServers is the status when autpilot has finished
	// transferring leadership and has demoted all the other versioned
	// servers but wants to indicate that more target version servers
	// are needed to replace all the existing other version servers.
	AutopilotUpgradeAwaitNewServers AutopilotUpgradeStatus = "await-new-servers"

	// AutopilotUpgradeAwaitServerRemoval is the status when autopilot is waiting
	// for the servers on non-target versions to be removed
	AutopilotUpgradeAwaitServerRemoval AutopilotUpgradeStatus = "await-server-removal"

	// AutopilotUpgradeDisabled is the status when automated ugprades are
	// disabled in the autopilot configuration
	AutopilotUpgradeDisabled AutopilotUpgradeStatus = "disabled"
)

// ReadableDuration is a duration type that is serialized to JSON in human readable format.
type ReadableDuration time.Duration

func NewReadableDuration(dur time.Duration) *ReadableDuration {
	d := ReadableDuration(dur)
	return &d
}

func (d *ReadableDuration) String() string {
	return d.Duration().String()
}

func (d *ReadableDuration) Duration() time.Duration {
	if d == nil {
		return time.Duration(0)
	}
	return time.Duration(*d)
}

func (d *ReadableDuration) MarshalJSON() ([]byte, error) {
	return []byte(fmt.Sprintf(`"%s"`, d.Duration().String())), nil
}

func (d *ReadableDuration) UnmarshalJSON(raw []byte) (err error) {
	if d == nil {
		return fmt.Errorf("cannot unmarshal to nil pointer")
	}

	var dur time.Duration
	str := string(raw)
	if len(str) >= 2 && str[0] == '"' && str[len(str)-1] == '"' {
		// quoted string
		dur, err = time.ParseDuration(str[1 : len(str)-1])
		if err != nil {
			return err
		}
	} else {
		// no quotes, not a string
		v, err := strconv.ParseFloat(str, 64)
		if err != nil {
			return err
		}
		dur = time.Duration(v)
	}

	*d = ReadableDuration(dur)
	return nil
}

// AutopilotGetConfiguration is used to query the current Autopilot configuration.
func (op *Operator) AutopilotGetConfiguration(q *QueryOptions) (*AutopilotConfiguration, error) {
	r := op.c.newRequest("GET", "/v1/operator/autopilot/configuration")
	r.setQueryOptions(q)
	_, resp, err := op.c.doRequest(r)
	if err != nil {
		return nil, err
	}
	defer closeResponseBody(resp)
	if err := requireOK(resp); err != nil {
		return nil, err
	}

	var out AutopilotConfiguration
	if err := decodeBody(resp, &out); err != nil {
		return nil, err
	}

	return &out, nil
}

// AutopilotSetConfiguration is used to set the current Autopilot configuration.
func (op *Operator) AutopilotSetConfiguration(conf *AutopilotConfiguration, q *WriteOptions) error {
	r := op.c.newRequest("PUT", "/v1/operator/autopilot/configuration")
	r.setWriteOptions(q)
	r.obj = conf
	_, resp, err := op.c.doRequest(r)
	if err != nil {
		return err
	}
	defer closeResponseBody(resp)
	if err := requireOK(resp); err != nil {
		return err
	}
	return nil
}

// AutopilotCASConfiguration is used to perform a Check-And-Set update on the
// Autopilot configuration. The ModifyIndex value will be respected. Returns
// true on success or false on failures.
func (op *Operator) AutopilotCASConfiguration(conf *AutopilotConfiguration, q *WriteOptions) (bool, error) {
	r := op.c.newRequest("PUT", "/v1/operator/autopilot/configuration")
	r.setWriteOptions(q)
	r.params.Set("cas", strconv.FormatUint(conf.ModifyIndex, 10))
	r.obj = conf
	_, resp, err := op.c.doRequest(r)
	if err != nil {
		return false, err
	}
	defer closeResponseBody(resp)
	if err := requireOK(resp); err != nil {
		return false, err
	}

	var buf bytes.Buffer
	if _, err := io.Copy(&buf, resp.Body); err != nil {
		return false, fmt.Errorf("Failed to read response: %v", err)
	}
	res := strings.Contains(buf.String(), "true")

	return res, nil
}

// AutopilotServerHealth
func (op *Operator) AutopilotServerHealth(q *QueryOptions) (*OperatorHealthReply, error) {
	r := op.c.newRequest("GET", "/v1/operator/autopilot/health")
	r.setQueryOptions(q)

	// we use 429 status to indicate unhealthiness
	_, resp, err := op.c.doRequest(r)
	if err != nil {
		return nil, err
	}
	defer closeResponseBody(resp)
	err = requireHttpCodes(resp, 200, 429)
	if err != nil {
		return nil, err
	}
	defer closeResponseBody(resp)

	var out OperatorHealthReply
	if err := decodeBody(resp, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

func (op *Operator) AutopilotState(q *QueryOptions) (*AutopilotState, error) {
	r := op.c.newRequest("GET", "/v1/operator/autopilot/state")
	r.setQueryOptions(q)
	_, resp, err := op.c.doRequest(r)
	if err != nil {
		return nil, err
	}
	defer closeResponseBody(resp)
	if err := requireOK(resp); err != nil {
		return nil, err
	}

	var out AutopilotState
	if err := decodeBody(resp, &out); err != nil {
		return nil, err
	}

	return &out, nil
}