package checker

import (
	"context"
	"fmt"

	sdk "git.happydns.org/checker-sdk-go/checker"
)

type apexLookupRule struct{}

func (apexLookupRule) Name() string { return "apex_lookup" }
func (apexLookupRule) Description() string {
	return "Verifies the zone apex (SOA) of the checked name can be located."
}

func (apexLookupRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
	data, errState := loadAlias(ctx, obs)
	if errState != nil {
		return errState
	}
	if data.Apex != "" {
		return okState(data.Apex, fmt.Sprintf("apex %s located", data.Apex))
	}
	return []sdk.CheckState{withHint(sdk.CheckState{
		Status:  sdk.StatusCrit,
		Subject: data.Owner,
		Message: fmt.Sprintf("could not locate zone apex: %s", data.ApexLookupError),
	}, "Check that the parent delegation exists and that the zone is published.")}
}

type cnameAtApexRule struct{}

func (cnameAtApexRule) Name() string { return "cname_at_apex" }
func (cnameAtApexRule) Description() string {
	return "Flags a CNAME at the zone apex, which conflicts with the SOA/NS records the apex must carry (RFC 1912 §2.4). Honours the shared allowApexCNAME option."
}

func (cnameAtApexRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, opts sdk.CheckerOptions) []sdk.CheckState {
	data, errState := loadAlias(ctx, obs)
	if errState != nil {
		return errState
	}
	if !apexKnown(data) {
		return skipped("apex lookup failed")
	}
	if !data.OwnerIsApex {
		return skipped("owner is not the zone apex")
	}
	if !data.ApexHasCNAME {
		return okState(data.Apex, "no CNAME at apex")
	}
	status := sdk.StatusCrit
	if allowApexCNAME(opts) {
		status = sdk.StatusWarn
	}
	return []sdk.CheckState{withHint(sdk.CheckState{
		Status:  status,
		Subject: data.Apex,
		Message: fmt.Sprintf("CNAME at apex %s conflicts with SOA/NS (RFC 1912 §2.4)", data.Apex),
	}, "Use the provider's ALIAS/ANAME flattening, an HTTP redirect, or move content to a sub-label such as www.")}
}

type apexFlatteningRule struct{}

func (apexFlatteningRule) Name() string { return "apex_flattening" }
func (apexFlatteningRule) Description() string {
	return "Notes ALIAS/ANAME provider-side flattening (A/AAAA served at apex alongside SOA/NS)."
}

func (apexFlatteningRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, opts sdk.CheckerOptions) []sdk.CheckState {
	data, errState := loadAlias(ctx, obs)
	if errState != nil {
		return errState
	}
	if !apexKnown(data) {
		return skipped("apex lookup failed")
	}
	if !data.OwnerIsApex {
		return skipped("owner is not the zone apex")
	}
	if !data.ApexFlattening {
		return okState(data.Apex, "no ALIAS/ANAME flattening detected")
	}
	if !recognizeApexFlattening(opts) {
		return skipped("recognizeApexFlattening disabled")
	}
	return []sdk.CheckState{withHint(sdk.CheckState{
		Status:  sdk.StatusInfo,
		Subject: data.Apex,
		Message: fmt.Sprintf("apex %s serves A/AAAA directly (provider-side ALIAS/ANAME flattening)", data.Apex),
	}, "Keep the upstream target's TTL in mind: apex A/AAAA will only update as fast as the provider re-flattens.")}
}