package npcregistry

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/npcs/identity"
)

func validList() dnd.NPCRegistry {
	return dnd.NPCRegistry{NPCs: []dnd.NPC{{
		ID:         identity.DeriveID("Mira Thorn"),
		Name:       "Mira Thorn",
		SourceRefs: []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 1, EndUnitID: 2}},
	}}}
}

func TestCodecMatchesMaintainedDurableFixture(t *testing.T) {
	raw, err := os.ReadFile("testdata/dnd_npc_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)
	}
	want := validList()
	if !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 stable durable JSON %s", encoded, compact.Bytes())
	}
}

func TestCodecOwnsDurableSchemaAndRegistersExactType(t *testing.T) {
	codec := New()
	schema := codec.Schema()
	if codec.Kind() != dnd.NPCRegistryKind || 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 NPC 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)
	}
	spec, ok := registry.Spec(dnd.NPCRegistryKind)
	if !ok || spec.SchemaDigest != contracts.DigestArtifactSchema(schema) {
		t.Fatalf("registered spec = %#v, %t", spec, ok)
	}
}

func TestCodecStrictlyRejectsMalformedOrUnknownJSON(t *testing.T) {
	codec := New()
	tests := []struct {
		name string
		raw  string
		want string
	}{
		{name: "unknown top-level", raw: `{"npcs":[],"unexpected":true}`, want: "unknown field"},
		{name: "unknown nested", raw: `{"npcs":[{"id":"x","name":"Mira","source_refs":[{"source_id":"s","start_unit_id":1,"end_unit_id":1}],"unexpected":true}]}`, want: "unknown field"},
		{name: "trailing", raw: `{"npcs":[]} {}`, want: "multiple JSON values"},
		{name: "missing array", raw: `{}`, want: "npcs must be present"},
		{name: "invalid reference", raw: `{"npcs":[{"id":"npc:sha256:0000000000000000000000000000000000000000000000000000000000000000","name":"Mira","source_refs":[{"source_id":"s","start_unit_id":0,"end_unit_id":1}]}]}`, want: "start_unit_id"},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			_, err := codec.Decode([]byte(test.raw))
			if err == nil || !strings.Contains(err.Error(), test.want) {
				t.Fatalf("Decode() error = %v, want %q", err, test.want)
			}
		})
	}
}

func TestCodecCandidatePreservesInvalidTypedValues(t *testing.T) {
	codec := New()
	candidate := dnd.NPCRegistry{NPCs: []dnd.NPC{{Name: "Mira Thorn", SourceRefs: []source.SourceRef{}}}}
	content, err := codec.EncodeCandidate(candidate)
	if err != nil || !json.Valid(content) {
		t.Fatalf("EncodeCandidate() = %s, %v; want JSON", content, 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(), ".id must match npc ID pattern") {
		t.Fatalf("Encode() error = %v, want strict validation error", err)
	}
}

func TestCodecRejectsInvalidDurableRangesWhileCandidatesPreserveThem(t *testing.T) {
	codec := New()
	for _, test := range []struct {
		name   string
		mutate func(*dnd.NPCRegistry)
		want   string
	}{
		{name: "nonpositive start", mutate: func(value *dnd.NPCRegistry) { value.NPCs[0].SourceRefs[0].StartUnitID = 0 }, want: "start_unit_id"},
		{name: "nonpositive end", mutate: func(value *dnd.NPCRegistry) { value.NPCs[0].SourceRefs[0].EndUnitID = 0 }, want: "end_unit_id"},
		{name: "reversed", mutate: func(value *dnd.NPCRegistry) {
			value.NPCs[0].SourceRefs[0].StartUnitID = 2
			value.NPCs[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 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("Mira Thorn"))
	if nameOffset < 0 {
		t.Fatal("candidate JSON does not contain NPC name")
	}
	content[nameOffset] = 'X'
	if first.NPCs[0].Name != "Mira Thorn" {
		t.Fatal("DecodeCandidate() retained input bytes")
	}
	first.NPCs[0].Name = "changed"
	first.NPCs[0].SourceRefs[0].SourceID = "changed"
	if input.NPCs[0].Name != "Mira Thorn" || input.NPCs[0].SourceRefs[0].SourceID != "session-alpha" {
		t.Fatal("DecodeCandidate() retained input values")
	}
	if second.NPCs[0].Name != "Mira Thorn" || second.NPCs[0].SourceRefs[0].SourceID != "session-alpha" {
		t.Fatal("DecodeCandidate() returned aliased values")
	}
}

func TestCodecRejectsEveryRequiredShapeBoundary(t *testing.T) {
	base := validList().NPCs[0]
	tests := []struct {
		name  string
		value dnd.NPCRegistry
		want  string
	}{
		{name: "blank name", value: dnd.NPCRegistry{NPCs: []dnd.NPC{{ID: base.ID, Name: " ", SourceRefs: base.SourceRefs}}}, want: "name must not be empty"},
		{name: "empty source refs", value: dnd.NPCRegistry{NPCs: []dnd.NPC{{ID: base.ID, Name: base.Name, SourceRefs: []source.SourceRef{}}}}, want: "source_refs must not be empty"},
	}
	for _, test := range tests {
		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)
			}
		})
	}
}

func TestCodecSchemaAndMetadataAreDefensive(t *testing.T) {
	codec := New()
	first := codec.Schema()
	first.JSONSchema[0] = '['
	second := codec.Schema()
	if !json.Valid(second.JSONSchema) || second.JSONSchema[0] == '[' {
		t.Fatal("Schema() returned shared bytes")
	}
	metadata := codec.Metadata(validList())
	metadata["other"] = true
	if next := codec.Metadata(validList()); len(next) != 1 || next["npc_count"] != 1 {
		t.Fatalf("Metadata() = %#v, want only npc_count", next)
	}
}
