package checker

import (
	"context"
	"encoding/json"
	"maps"
	"testing"

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

// stubObs implements the minimal subset of sdk.ObservationGetter the rules use.
type stubObs struct {
	data *ObservationData
	err  error
}

func (s stubObs) Get(_ context.Context, _ sdk.ObservationKey, dst any) error {
	if s.err != nil {
		return s.err
	}
	b, err := json.Marshal(s.data)
	if err != nil {
		return err
	}
	return json.Unmarshal(b, dst)
}

func (s stubObs) GetRelated(_ context.Context, _ sdk.ObservationKey) ([]sdk.RelatedObservation, error) {
	return nil, nil
}

func mkOpts(kv map[string]any) sdk.CheckerOptions {
	out := sdk.CheckerOptions{}
	maps.Copy(out, kv)
	return out
}

func TestNSDeclaredRule(t *testing.T) {
	rule := &nsDeclaredRule{}

	t.Run("ok with two NS", func(t *testing.T) {
		d := &ObservationData{
			DeclaredNS: []string{"ns1.example.com.", "ns2.example.com."},
			Probed:     []string{"ns1.example.com.", "ns2.example.com."},
		}
		states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(nil))
		if len(states) != 1 || states[0].Status != sdk.StatusOK {
			t.Errorf("expected OK, got %#v", states)
		}
	})

	t.Run("too few NS", func(t *testing.T) {
		d := &ObservationData{
			DeclaredNS: []string{"ns1.example.com."},
			Probed:     []string{"ns1.example.com."},
		}
		states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(map[string]any{"minNameServers": 2}))
		if len(states) != 1 || states[0].Code != CodeTooFewNS {
			t.Errorf("expected TooFewNS, got %#v", states)
		}
	})

	t.Run("no NS at all", func(t *testing.T) {
		d := &ObservationData{}
		states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(map[string]any{"useParentNS": false}))
		var hasNoNS bool
		for _, st := range states {
			if st.Code == CodeNoNS {
				hasNoNS = true
			}
		}
		if !hasNoNS {
			t.Errorf("expected NoNS finding, got %#v", states)
		}
	})
}

func TestNSReachableRule(t *testing.T) {
	rule := &nsReachableRule{}

	t.Run("UDP fail is critical", func(t *testing.T) {
		d := &ObservationData{
			Probed: []string{"ns1."},
			Results: map[string]*NSResult{
				"ns1.": {UDPReachable: false, TCPReachable: false},
			},
		}
		states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(nil))
		if len(states) != 1 || states[0].Code != CodeNSUDPFailed || states[0].Status != sdk.StatusCrit {
			t.Errorf("expected critical UDP fail, got %#v", states)
		}
	})

	t.Run("TCP fail crit when requireTCP", func(t *testing.T) {
		d := &ObservationData{
			Probed: []string{"ns1."},
			Results: map[string]*NSResult{
				"ns1.": {UDPReachable: true, TCPReachable: false},
			},
		}
		states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(map[string]any{"requireTCP": true}))
		if len(states) != 1 || states[0].Code != CodeNSTCPFailed || states[0].Status != sdk.StatusCrit {
			t.Errorf("got %#v", states)
		}
	})

	t.Run("TCP fail warn when not required", func(t *testing.T) {
		d := &ObservationData{
			Probed: []string{"ns1."},
			Results: map[string]*NSResult{
				"ns1.": {UDPReachable: true, TCPReachable: false},
			},
		}
		states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(map[string]any{"requireTCP": false}))
		if len(states) != 1 || states[0].Status != sdk.StatusWarn {
			t.Errorf("got %#v", states)
		}
	})
}

func TestAuthoritativeRule_Lame(t *testing.T) {
	rule := &authoritativeRule{}
	d := &ObservationData{
		Zone:   "example.com.",
		HasSOA: true,
		Probed: []string{"ns1."},
		Results: map[string]*NSResult{
			"ns1.": {UDPReachable: true, Authoritative: false},
		},
	}
	states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(nil))
	if len(states) != 1 || states[0].Code != CodeLame {
		t.Errorf("expected lame finding, got %#v", states)
	}
}

func TestLatencyRule(t *testing.T) {
	rule := &latencyRule{}
	d := &ObservationData{
		Probed: []string{"fast.", "slow."},
		Results: map[string]*NSResult{
			"fast.": {UDPReachable: true, LatencyMs: 50},
			"slow.": {UDPReachable: true, LatencyMs: 1000},
		},
	}
	states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(map[string]any{"latencyThresholdMs": 500}))
	if len(states) != 1 || states[0].Code != CodeSlowNS || states[0].Subject != "slow." {
		t.Errorf("expected single slow finding for slow., got %#v", states)
	}
}

func TestParentDelegationRule_Drift(t *testing.T) {
	rule := &parentDelegationRule{}
	d := &ObservationData{
		DeclaredNS: []string{"ns1.example.com.", "ns2.example.com."},
		ParentNS:   []string{"ns1.example.com.", "ns3.example.com."},
	}
	states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(nil))
	if len(states) != 1 || states[0].Code != CodeParentDrift {
		t.Errorf("expected ParentDrift, got %#v", states)
	}
}

func TestParentDelegationRule_QueryFailed(t *testing.T) {
	rule := &parentDelegationRule{}
	d := &ObservationData{ParentQueryError: "boom"}
	states := rule.Evaluate(context.Background(), stubObs{data: d}, mkOpts(nil))
	if len(states) != 1 || states[0].Code != CodeParentQueryFailed {
		t.Errorf("expected ParentQueryFailed, got %#v", states)
	}
}

func TestRulesRegistry(t *testing.T) {
	rules := Rules()
	if len(rules) == 0 {
		t.Fatal("Rules() returned empty list")
	}
	seen := map[string]bool{}
	for _, r := range rules {
		name := r.Name()
		if name == "" {
			t.Error("rule with empty name")
		}
		if seen[name] {
			t.Errorf("duplicate rule name: %s", name)
		}
		seen[name] = true
		if r.Description() == "" {
			t.Errorf("rule %s has empty description", name)
		}
	}
}