package locationregistry

import (
	"bytes"
	"encoding/json"
	"os"
	"reflect"
	"strings"
	"testing"

	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
	"gitea.maximumdirect.net/eric/notarius/internal/framework/pipeline"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/locations/identity"
)

func validList() dnd.LocationRegistry {
	refs := []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 1, EndUnitID: 2}}
	return dnd.LocationRegistry{Locations: []dnd.Location{{
		ID:         identity.DeriveID("The Old Tavern", refs),
		Name:       "The Old Tavern",
		SourceRefs: refs,
	}}}
}

func TestCodecMatchesMaintainedDurableFixture(t *testing.T) {
	raw, err := os.ReadFile("testdata/dnd_location_registry.v1.json")
	if err != nil {
		t.Fatalf("read durable fixture: %v", err)
	}
	codec := New()
	value, err := codec.Decode(raw)
	if err != nil {
		t.Fatalf("Decode() error = %v, want nil", err)
	}
	if want := validList(); !reflect.DeepEqual(value, want) {
		t.Fatalf("Decode() = %#v, want %#v", value, want)
	}
	encoded, err := codec.Encode(value)
	if err != nil {
		t.Fatalf("Encode() error = %v, want nil", err)
	}
	var compact bytes.Buffer
	if err := json.Compact(&compact, raw); err != nil {
		t.Fatalf("compact durable fixture: %v", err)
	}
	if !bytes.Equal(encoded, compact.Bytes()) {
		t.Fatalf("Encode() = %s, want %s", encoded, compact.Bytes())
	}
}

func TestCodecOwnsDurableSchemaAndMetadata(t *testing.T) {
	codec := New()
	schema := codec.Schema()
	if codec.Kind() != dnd.LocationRegistryKind || codec.MediaType() != MediaType {
		t.Fatalf("codec identity = %q/%q", codec.Kind(), codec.MediaType())
	}
	if schema.ID != SchemaID || schema.Name != SchemaName || schema.Version != SchemaVersion || !json.Valid(schema.JSONSchema) {
		t.Fatalf("schema = %#v, want durable location schema", schema)
	}
	var document map[string]any
	if err := json.Unmarshal(schema.JSONSchema, &document); err != nil || document["$id"] != SchemaID {
		t.Fatalf("durable schema document = %#v, %v", document, err)
	}
	registry := pipeline.NewArtifactCodecRegistry()
	if err := pipeline.RegisterArtifactCodec(registry, codec); err != nil {
		t.Fatalf("RegisterArtifactCodec() error = %v", err)
	}
	if spec, ok := registry.Spec(dnd.LocationRegistryKind); !ok || spec.SchemaDigest != contracts.DigestArtifactSchema(schema) {
		t.Fatalf("registered spec = %#v, %t", spec, ok)
	}
	first := schema.JSONSchema
	first[0] = '['
	if next := codec.Schema().JSONSchema; !json.Valid(next) || next[0] == '[' {
		t.Fatal("Schema() returned shared bytes")
	}
	metadata := codec.Metadata(validList())
	metadata["other"] = true
	if next := codec.Metadata(validList()); len(next) != 1 || next["location_count"] != 1 {
		t.Fatalf("Metadata() = %#v", next)
	}
}

func TestCodecSupportsEmptyListsAndCandidateSemanticFailures(t *testing.T) {
	codec := New()
	empty := dnd.LocationRegistry{Locations: []dnd.Location{}}
	if content, err := codec.Encode(empty); err != nil || string(content) != `{"locations":[]}` {
		t.Fatalf("Encode() = %s, %v", content, err)
	}
	for _, candidate := range []dnd.LocationRegistry{
		{},
		empty,
		{Locations: []dnd.Location{{ID: "bad", Name: " ", SourceRefs: nil}}},
		{Locations: []dnd.Location{{ID: "bad", Name: " ", SourceRefs: []source.SourceRef{}}}},
		{Locations: []dnd.Location{{ID: "bad", Name: " ", SourceRefs: []source.SourceRef{{StartUnitID: 0, EndUnitID: -1}}}}},
	} {
		content, err := codec.EncodeCandidate(candidate)
		if err != nil || !json.Valid(content) {
			t.Fatalf("EncodeCandidate() = %s, %v", content, err)
		}
		decoded, err := codec.DecodeCandidate(content)
		if err != nil || !reflect.DeepEqual(decoded, candidate) {
			t.Fatalf("DecodeCandidate() = %#v, %v, want %#v", decoded, err, candidate)
		}
	}
}

func TestCodecCandidateDecodeOwnsValues(t *testing.T) {
	codec := New()
	input := validList()
	content, err := codec.EncodeCandidate(input)
	if err != nil {
		t.Fatal(err)
	}
	first, err := codec.DecodeCandidate(content)
	if err != nil {
		t.Fatal(err)
	}
	second, err := codec.DecodeCandidate(content)
	if err != nil {
		t.Fatal(err)
	}
	nameOffset := bytes.Index(content, []byte("The Old Tavern"))
	if nameOffset < 0 {
		t.Fatal("candidate JSON does not contain location name")
	}
	content[nameOffset] = 'X'
	if first.Locations[0].Name != "The Old Tavern" {
		t.Fatal("DecodeCandidate() retained input bytes")
	}
	first.Locations[0].Name = "changed"
	first.Locations[0].SourceRefs[0].SourceID = "changed"
	if input.Locations[0].Name != "The Old Tavern" || input.Locations[0].SourceRefs[0].SourceID != "session-alpha" {
		t.Fatal("DecodeCandidate() retained input values")
	}
	if second.Locations[0].Name != "The Old Tavern" || second.Locations[0].SourceRefs[0].SourceID != "session-alpha" {
		t.Fatal("DecodeCandidate() returned aliased values")
	}
}

func TestCodecRejectsInvalidDurableRangesWhileCandidatesPreserveThem(t *testing.T) {
	codec := New()
	for _, test := range []struct {
		name   string
		mutate func(*dnd.LocationRegistry)
		want   string
	}{
		{name: "nonpositive start", mutate: func(value *dnd.LocationRegistry) { value.Locations[0].SourceRefs[0].StartUnitID = 0 }, want: "start_unit_id"},
		{name: "nonpositive end", mutate: func(value *dnd.LocationRegistry) { value.Locations[0].SourceRefs[0].EndUnitID = 0 }, want: "end_unit_id"},
		{name: "reversed", mutate: func(value *dnd.LocationRegistry) {
			value.Locations[0].SourceRefs[0].StartUnitID = 2
			value.Locations[0].SourceRefs[0].EndUnitID = 1
		}, want: "must not exceed"},
	} {
		t.Run(test.name, func(t *testing.T) {
			candidate := validList()
			test.mutate(&candidate)
			content, err := codec.EncodeCandidate(candidate)
			if err != nil {
				t.Fatalf("EncodeCandidate() error = %v", err)
			}
			decoded, err := codec.DecodeCandidate(content)
			if err != nil || !reflect.DeepEqual(decoded, candidate) {
				t.Fatalf("DecodeCandidate() = %#v, %v; want %#v", decoded, err, candidate)
			}
			if _, err := codec.Encode(candidate); err == nil || !strings.Contains(err.Error(), test.want) {
				t.Fatalf("Encode() error = %v, want %q", err, test.want)
			}
			if _, err := codec.Decode(content); err == nil || !strings.Contains(err.Error(), test.want) {
				t.Fatalf("Decode() error = %v, want %q", err, test.want)
			}
		})
	}
}

func TestCodecRejectsStructuralJSONBeforeSemanticApproval(t *testing.T) {
	valid := `{"locations":[{"id":"location:sha256:0000000000000000000000000000000000000000000000000000000000000000","name":"The Tavern","source_refs":[{"source_id":"session","start_unit_id":1,"end_unit_id":1}]}]}`
	for _, test := range []struct{ name, raw, want string }{
		{"malformed", `{`, "decode dnd location registry"},
		{"unknown top-level", `{"locations":[],"unexpected":true}`, "unknown field"},
		{"unknown location field", strings.Replace(valid, `"name":"The Tavern"`, `"name":"The Tavern","unexpected":true`, 1), "unknown field"},
		{"unknown source reference field", strings.Replace(valid, `"end_unit_id":1`, `"end_unit_id":1,"unexpected":true`, 1), "unknown field"},
		{"invalid type", `{"locations":"not-an-array"}`, "cannot unmarshal string"},
		{"trailing", `{"locations":[]} {}`, "multiple JSON values"},
	} {
		t.Run(test.name, func(t *testing.T) {
			if _, err := New().DecodeCandidate([]byte(test.raw)); err == nil || !strings.Contains(err.Error(), test.want) {
				t.Fatalf("DecodeCandidate() error = %v, want %q", err, test.want)
			}
		})
	}
}

func TestCodecRejectsApprovedShapeBoundaries(t *testing.T) {
	base := validList().Locations[0]
	for _, test := range []struct {
		name  string
		value dnd.LocationRegistry
		want  string
	}{
		{"nil locations", dnd.LocationRegistry{}, "locations must be present"},
		{"invalid ID", dnd.LocationRegistry{Locations: []dnd.Location{{ID: "bad", Name: base.Name, SourceRefs: base.SourceRefs}}}, "id must match location ID pattern"},
		{"blank name", dnd.LocationRegistry{Locations: []dnd.Location{{ID: base.ID, Name: " ", SourceRefs: base.SourceRefs}}}, "name must not be empty"},
		{"empty source refs", dnd.LocationRegistry{Locations: []dnd.Location{{ID: base.ID, Name: base.Name, SourceRefs: nil}}}, "source_refs must contain"},
		{"malformed source reference", dnd.LocationRegistry{Locations: []dnd.Location{{ID: base.ID, Name: base.Name, SourceRefs: []source.SourceRef{{SourceID: "session", StartUnitID: 0, EndUnitID: 1}}}}}, "start_unit_id must be positive"},
	} {
		t.Run(test.name, func(t *testing.T) {
			if _, err := New().Encode(test.value); err == nil || !strings.Contains(err.Error(), test.want) {
				t.Fatalf("Encode() error = %v, want %q", err, test.want)
			}
		})
	}
}
