package updateprotocol

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"
)

var releaseVersionPattern = regexp.MustCompile(`^v(?:0|[1-9][0-9]*)\.(?:0|[1-9][0-9]*)\.(?:0|[1-9][0-9]*)$`)

const (
	PhaseIdle       = "idle"
	PhaseQueued     = "queued"
	PhasePulling    = "pulling"
	PhaseRestarting = "restarting"
	PhaseVerifying  = "verifying"
	PhaseComplete   = "complete"
	PhaseFailed     = "failed"
)

type Request struct {
	Version          string `json:"version"`
	CurrentVersion   string `json:"current_version"`
	RegistryUsername string `json:"registry_username"`
	// RegistryToken keeps the v2 wire name for compatibility and carries either
	// a registry password or an API token.
	RegistryToken string `json:"registry_token"`
}

type Status struct {
	// Optional capability; older v2 agents require registry credentials.
	AnonymousPull bool      `json:"anonymous_pull,omitempty"`
	Phase         string    `json:"phase"`
	TargetVersion string    `json:"target_version,omitempty"`
	Message       string    `json:"message,omitempty"`
	StartedAt     time.Time `json:"started_at,omitempty"`
	UpdatedAt     time.Time `json:"updated_at,omitempty"`
	AgentVersion  string    `json:"agent_version,omitempty"`
	Protocol      int       `json:"protocol_version,omitempty"`
}

func (s Status) Busy() bool {
	return s.Phase == PhaseQueued || s.Phase == PhasePulling || s.Phase == PhaseRestarting || s.Phase == PhaseVerifying
}

func ValidVersion(version string) bool {
	return len(version) <= 64 && releaseVersionPattern.MatchString(version)
}

// CompareVersions compares strict stable vMAJOR.MINOR.PATCH versions. It does
// not require callers to install intermediate releases.
func CompareVersions(left, right string) (int, error) {
	a, err := parseVersion(left)
	if err != nil {
		return 0, err
	}
	b, err := parseVersion(right)
	if err != nil {
		return 0, err
	}
	for index := range a {
		if a[index] < b[index] {
			return -1, nil
		}
		if a[index] > b[index] {
			return 1, nil
		}
	}
	return 0, nil
}

func parseVersion(raw string) ([3]int, error) {
	if !ValidVersion(raw) {
		return [3]int{}, fmt.Errorf("version must use vMAJOR.MINOR.PATCH")
	}
	parts := strings.Split(strings.TrimPrefix(raw, "v"), ".")
	var values [3]int
	for index, part := range parts {
		value, err := strconv.Atoi(part)
		if err != nil || value < 0 || value > 1_000_000 {
			return [3]int{}, fmt.Errorf("version contains an invalid number")
		}
		values[index] = value
	}
	return values, nil
}