package v2

import (
	"errors"
	"fmt"

	"edge-infra.dev/pkg/sds/lib/set"
)

var (
	errV1AndV2SpecSpecified         = errors.New("V1 spec cannot be specified alongside V2 spec")
	errStandByLongerThanSuspendTime = errors.New("stand-by time cannot be longer than suspend time")
	errSuspendLongerThanOffTime     = errors.New("suspend time cannot be longer than off time")
)

// Validates the DisplayConfig, checking:
//   - V1 spec is valid and not configured alongside V2 spec.
//   - All display-ports are unique.
//   - MPID and supported resolutions are not configured in spec.
//   - Only one display is configured as the primary.
//   - DPMS configuration is valid (standby-time < suspend-time < off-time).
func (displayConfig *DisplayConfig) Validate() error {
	if displayConfig == nil {
		return nil
	}

	if displayConfig.V1 != nil {
		return validateV1(displayConfig)
	}

	if err := validateNonSettableFields(displayConfig); err != nil {
		return err
	}

	if err := validateDisplayPorts(displayConfig); err != nil {
		return err
	}

	if err := validatePrimary(displayConfig); err != nil {
		return err
	}

	return validateDPMS(displayConfig)
}

// V1 and V2 spec cannot both be configured.
//
// V1 spec must be valid.
func validateV1(displayConfig *DisplayConfig) error {
	if displayConfig.Displays != nil || displayConfig.Layout != nil || displayConfig.DPMS != nil {
		return errV1AndV2SpecSpecified
	}
	return displayConfig.V1.Validate()
}

// Display-ports must be unique for displays and layout.
func validateDisplayPorts(displayConfig *DisplayConfig) error {
	displayDPs := set.Set[DisplayPort]{}
	for _, dp := range displayConfig.Displays.DisplayPorts() {
		if _, ok := displayDPs[dp]; ok {
			return fmt.Errorf("display display-ports must be unique, multiple displays use '%s'", dp)
		}
		displayDPs.Add(dp)
	}

	layoutDPs := set.Set[DisplayPort]{}
	for _, dp := range displayConfig.Layout {
		if _, ok := layoutDPs[dp]; ok {
			return fmt.Errorf("layout display-ports must be unique, multiple entries for '%s'", dp)
		}
		layoutDPs.Add(dp)
	}

	return nil
}

// Displays cannot configure MPID or supported resolution.
func validateNonSettableFields(displayConfig *DisplayConfig) error {
	for _, display := range displayConfig.Displays {
		if display.MPID != nil {
			return fmt.Errorf("display %s specified 'MPID': this must not be configured in the NodeDisplayConfig spec", display.DisplayPort)
		}
		if display.SupportedResolutions != nil {
			return fmt.Errorf("display %s specified 'supportedResolutions': resolution must be configured via the 'resolution' field", display.DisplayPort)
		}
	}
	return nil
}

// Only one display can be the primary.
func validatePrimary(displayConfig *DisplayConfig) error {
	primaries := []DisplayPort{}
	for _, display := range displayConfig.Displays {
		if display.IsPrimary() {
			primaries = append(primaries, display.DisplayPort)
		}
	}

	if len(primaries) > 1 {
		return fmt.Errorf("there can only be one primary, found %d: %v", len(primaries), primaries)
	}

	return nil
}

// Validates DPMS configuration.
//
// Where these fields are set, they must be configured so
// standby-time < suspend-time < off-time.
//
// If a field is not set, it is assumed to be 0.
func validateDPMS(displayConfig *DisplayConfig) error {
	if displayConfig.DPMS == nil {
		return nil
	}

	var standybyTime, suspendTimeTime, offTimeTime int
	if displayConfig.DPMS.StandbyTime != nil {
		standybyTime = *displayConfig.DPMS.StandbyTime
	}
	if displayConfig.DPMS.SuspendTime != nil {
		suspendTimeTime = *displayConfig.DPMS.SuspendTime
	}
	if displayConfig.DPMS.OffTime != nil {
		offTimeTime = *displayConfig.DPMS.OffTime
	}

	if standybyTime > suspendTimeTime {
		return errStandByLongerThanSuspendTime
	} else if suspendTimeTime > offTimeTime {
		return errSuspendLongerThanOffTime
	}

	return nil
}