package checker

import (
	"context"
	"fmt"
	"slices"
	"strings"

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

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

type xmppRule struct{}

func (r *xmppRule) Name() string {
	return "xmpp_server"
}

func (r *xmppRule) Description() string {
	return "Checks discovery, STARTTLS, SASL and federation auth of an XMPP server"
}

func (r *xmppRule) ValidateOptions(opts sdk.CheckerOptions) error {
	if v, ok := opts["mode"]; ok {
		if s, ok := v.(string); ok && s != "" && !slices.Contains(validModes, s) {
			return fmt.Errorf(`mode must be "c2s", "s2s", or "both"`)
		}
	}
	return nil
}

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

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

	// Fold related TLS observations (from a downstream TLS checker, if any)
	// into the XMPP issue list so cert/chain problems show up on the XMPP
	// service page without requiring a separate glance at the TLS checker.
	related, _ := obs.GetRelated(ctx, TLSRelatedKey)
	issues = append(issues, tlsIssuesFromRelated(related)...)

	// Reduce issue list to the worst severity.
	worst := sdk.StatusOK
	critMsgs, warnMsgs := []string{}, []string{}
	var firstCritCode, firstWarnCode string

	for _, is := range issues {
		switch is.Severity {
		case SeverityCrit:
			if worst < sdk.StatusCrit {
				worst = sdk.StatusCrit
			}
			if firstCritCode == "" {
				firstCritCode = is.Code
			}
			critMsgs = append(critMsgs, is.Message)
		case SeverityWarn:
			if worst < sdk.StatusWarn {
				worst = sdk.StatusWarn
			}
			if firstWarnCode == "" {
				firstWarnCode = is.Code
			}
			warnMsgs = append(warnMsgs, is.Message)
		}
	}

	mode, _ := sdk.GetOption[string](opts, "mode")
	if mode == "" {
		mode = "both"
	}
	wantC2S := mode != "s2s"
	wantS2S := mode != "c2s"

	// Even without issues, the check isn't OK unless we got at least one
	// working endpoint in each requested mode.
	if (wantC2S && !data.Coverage.WorkingC2S) || (wantS2S && !data.Coverage.WorkingS2S) {
		if worst < sdk.StatusCrit {
			worst = sdk.StatusCrit
		}
		var missing []string
		if wantC2S && !data.Coverage.WorkingC2S {
			missing = append(missing, "c2s")
		}
		if wantS2S && !data.Coverage.WorkingS2S {
			missing = append(missing, "s2s")
		}
		critMsgs = append(critMsgs, "no working "+strings.Join(missing, "/")+" endpoint")
		if firstCritCode == "" {
			firstCritCode = CodeAllEndpointsDown
		}
	}

	meta := map[string]any{
		"working_c2s": data.Coverage.WorkingC2S,
		"working_s2s": data.Coverage.WorkingS2S,
		"has_ipv4":    data.Coverage.HasIPv4,
		"has_ipv6":    data.Coverage.HasIPv6,
		"endpoints":   len(data.Endpoints),
		"issue_count": len(data.Issues),
	}

	switch worst {
	case sdk.StatusOK:
		return []sdk.CheckState{{
			Status:  sdk.StatusOK,
			Message: fmt.Sprintf("XMPP operational (c2s=%v, s2s=%v, %d endpoints)", data.Coverage.WorkingC2S, data.Coverage.WorkingS2S, len(data.Endpoints)),
			Code:    "xmpp.ok",
			Meta:    meta,
		}}
	case sdk.StatusWarn:
		return []sdk.CheckState{{
			Status:  sdk.StatusWarn,
			Message: "XMPP works with warnings: " + joinTop(warnMsgs, 2),
			Code:    firstWarnCode,
			Meta:    meta,
		}}
	default:
		return []sdk.CheckState{{
			Status:  sdk.StatusCrit,
			Message: "XMPP broken: " + joinTop(critMsgs, 2),
			Code:    firstCritCode,
			Meta:    meta,
		}}
	}
}

func joinTop(msgs []string, n int) string {
	if len(msgs) == 0 {
		return ""
	}
	if len(msgs) <= n {
		return strings.Join(msgs, "; ")
	}
	return strings.Join(msgs[:n], "; ") + fmt.Sprintf(" (+%d more)", len(msgs)-n)
}