package checker

import (
	"context"
	"fmt"

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

func Rule() sdk.CheckRule {
	return &smtpRule{}
}

type smtpRule struct{}

func (r *smtpRule) Name() string {
	return "smtp_server"
}

func (r *smtpRule) Description() string {
	return "Checks MX discovery, SMTP connectivity, STARTTLS, PTR/FCrDNS and mail-acceptance posture for an email-receiving domain"
}

func (r *smtpRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, opts sdk.CheckerOptions) []sdk.CheckState {
	var data SMTPData
	if err := obs.Get(ctx, ObservationKeySMTP, &data); err != nil {
		return []sdk.CheckState{{
			Status:  sdk.StatusError,
			Message: fmt.Sprintf("failed to load SMTP observation: %v", err),
			Code:    "smtp.observation_error",
		}}
	}

	// Null-MX is a *declared* refusal of mail; it's an INFO, not a fail.
	if data.MX.NullMX {
		return []sdk.CheckState{{
			Status:  sdk.StatusInfo,
			Message: "Domain refuses all email via null MX (RFC 7505).",
			Code:    CodeNullMX,
			Meta: map[string]any{
				"null_mx": true,
			},
		}}
	}

	issues := append([]Issue(nil), data.Issues...)

	// Fold related TLS observations so cert/chain problems show up on the
	// SMTP service page without requiring the user to open a separate
	// report.
	related, _ := obs.GetRelated(ctx, TLSRelatedKey)
	issues = append(issues, tlsIssuesFromRelated(related)...)

	if len(issues) == 0 {
		return []sdk.CheckState{{
			Status:  sdk.StatusOK,
			Message: fmt.Sprintf("SMTP operational (%d MX, %d endpoints, TLS=%v)", len(data.MX.Records), len(data.Endpoints), data.Coverage.AllSTARTTLS),
			Code:    "smtp.ok",
			Meta: map[string]any{
				"has_ipv4":        data.Coverage.HasIPv4,
				"has_ipv6":        data.Coverage.HasIPv6,
				"any_starttls":    data.Coverage.AnySTARTTLS,
				"all_starttls":    data.Coverage.AllSTARTTLS,
				"all_accept_mail": data.Coverage.AllAcceptMail,
				"mx_count":        len(data.MX.Records),
				"endpoint_count":  len(data.Endpoints),
			},
		}}
	}

	out := make([]sdk.CheckState, 0, len(issues))
	for _, is := range issues {
		status := sdk.StatusInfo
		switch is.Severity {
		case SeverityCrit:
			status = sdk.StatusCrit
		case SeverityWarn:
			status = sdk.StatusWarn
		}
		subject := is.Endpoint
		if subject == "" {
			subject = is.Target
		}
		meta := map[string]any{}
		if is.Fix != "" {
			meta["fix"] = is.Fix
		}
		if is.Endpoint != "" {
			meta["endpoint"] = is.Endpoint
		}
		if is.Target != "" {
			meta["target"] = is.Target
		}
		out = append(out, sdk.CheckState{
			Status:  status,
			Message: is.Message,
			Code:    is.Code,
			Subject: subject,
			Meta:    meta,
		})
	}
	return out
}