package llm

import (
	"context"
	"errors"
	"testing"

	"gitea.stevedudenhoeffer.com/steve/go-llm/v2/provider"
)

// recordingProvider captures the model name passed to Complete so tests can
// verify that Parse resolved to the correct model without network calls.
type recordingProvider struct {
	lastModel string
	// err, when non-nil, is returned from Complete so failover tests can drive
	// a comma-Parse'd chain through a failover decision. Defaults to nil (success).
	err error
}

func (p *recordingProvider) Complete(_ context.Context, req provider.Request) (provider.Response, error) {
	p.lastModel = req.Model
	if p.err != nil {
		return provider.Response{}, p.err
	}
	return provider.Response{Text: "ok"}, nil
}

func (p *recordingProvider) Stream(_ context.Context, _ provider.Request, events chan<- provider.StreamEvent) error {
	close(events)
	return nil
}

// testRegistry builds a Registry with two mock providers ("alpha" and "beta")
// and an injectable envLookup. No real API keys or network access required.
func testRegistry(envFn func(string) string) (*Registry, *recordingProvider, *recordingProvider) {
	alpha := &recordingProvider{}
	beta := &recordingProvider{}

	r := &Registry{
		providers: map[string]ProviderInfo{
			"alpha": {
				Name:        "alpha",
				DisplayName: "Alpha",
				EnvKey:      "ALPHA_API_KEY",
				Models:      []string{"model-a"},
				New: func(apiKey string, opts ...ClientOption) *Client {
					return NewClient(alpha)
				},
			},
			"beta": {
				Name:        "beta",
				DisplayName: "Beta",
				EnvKey:      "",
				Models:      []string{"model-b"},
				New: func(_ string, opts ...ClientOption) *Client {
					return NewClient(beta)
				},
			},
		},
		order:     []string{"alpha", "beta"},
		aliases:   make(map[string]string),
		envLookup: envFn,
	}
	return r, alpha, beta
}

// ---------------------------------------------------------------------------
// splitReasoning
// ---------------------------------------------------------------------------

func TestSplitReasoning(t *testing.T) {
	tests := []struct {
		input     string
		wantBase  string
		wantLevel ReasoningLevel
	}{
		{"gpt-4o", "gpt-4o", ""},
		{"gpt-4o:high", "gpt-4o", ReasoningHigh},
		{"gpt-4o:low", "gpt-4o", ReasoningLow},
		{"gpt-4o:medium", "gpt-4o", ReasoningMedium},
		{"qwen3:30b", "qwen3:30b", ""},                 // Ollama tag, not a level
		{"qwen3:30b:high", "qwen3:30b", ReasoningHigh}, // tag + reasoning
		{"model:", "model:", ""},                       // trailing colon, empty suffix
		{"", "", ""},                                   // empty string
		{"a:b:c:high", "a:b:c", ReasoningHigh},         // multiple colons
		{"a:b:c:30b", "a:b:c:30b", ""},                 // multiple colons, non-level
	}
	for _, tt := range tests {
		t.Run(tt.input, func(t *testing.T) {
			base, level := splitReasoning(tt.input)
			if base != tt.wantBase {
				t.Errorf("splitReasoning(%q) base = %q, want %q", tt.input, base, tt.wantBase)
			}
			if level != tt.wantLevel {
				t.Errorf("splitReasoning(%q) level = %q, want %q", tt.input, level, tt.wantLevel)
			}
		})
	}
}

// ---------------------------------------------------------------------------
// ParseDSN
// ---------------------------------------------------------------------------

func TestParseDSN(t *testing.T) {
	tests := []struct {
		name    string
		raw     string
		want    DSN
		wantErr bool
	}{
		{
			name: "full DSN with token",
			raw:  "foreman://test-token@foreman-m5.orgrimmar.dudenhoeffer.casa",
			want: DSN{Scheme: "foreman", Token: "test-token", Host: "foreman-m5.orgrimmar.dudenhoeffer.casa"},
		},
		{
			name: "no token",
			raw:  "ollama://localhost:11434",
			want: DSN{Scheme: "ollama", Token: "", Host: "localhost:11434"},
		},
		{
			name: "trailing slash stripped",
			raw:  "foreman://tok@host.com/",
			want: DSN{Scheme: "foreman", Token: "tok", Host: "host.com"},
		},
		{
			name: "with path",
			raw:  "foreman://tok@host.com/v1/api",
			want: DSN{Scheme: "foreman", Token: "tok", Host: "host.com/v1/api"},
		},
		{
			name:    "missing scheme",
			raw:     "no-scheme-here",
			wantErr: true,
		},
		{
			name:    "missing host",
			raw:     "foreman://token@",
			wantErr: true,
		},
		{
			name:    "empty string",
			raw:     "",
			wantErr: true,
		},
		{
			name:    "scheme only",
			raw:     "foreman://",
			wantErr: true,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := ParseDSN(tt.raw)
			if tt.wantErr {
				if err == nil {
					t.Fatalf("ParseDSN(%q) expected error, got nil", tt.raw)
				}
				if !errors.Is(err, ErrInvalidDSN) {
					t.Errorf("ParseDSN(%q) error = %v, want ErrInvalidDSN", tt.raw, err)
				}
				return
			}
			if err != nil {
				t.Fatalf("ParseDSN(%q) unexpected error: %v", tt.raw, err)
			}
			if got != tt.want {
				t.Errorf("ParseDSN(%q) = %+v, want %+v", tt.raw, got, tt.want)
			}
		})
	}
}

// ---------------------------------------------------------------------------
// Registry.Parse
// ---------------------------------------------------------------------------

func TestRegistryParse(t *testing.T) {
	t.Run("basic provider/model", func(t *testing.T) {
		r, alpha, _ := testRegistry(nil)
		m, err := r.Parse("alpha/model-a")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m == nil {
			t.Fatal("expected non-nil model")
		}
		// Verify the model name by exercising it.
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "model-a" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "model-a")
		}
	})

	t.Run("provider/model with reasoning suffix", func(t *testing.T) {
		r, alpha, _ := testRegistry(nil)
		m, err := r.Parse("alpha/model-a:high")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m.defaultReasoning != ReasoningHigh {
			t.Errorf("reasoning = %q, want %q", m.defaultReasoning, ReasoningHigh)
		}
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "model-a" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "model-a")
		}
	})

	t.Run("ollama-style tag preserved", func(t *testing.T) {
		r, _, beta := testRegistry(nil)
		m, err := r.Parse("beta/qwen3:30b")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m.defaultReasoning != "" {
			t.Errorf("reasoning = %q, want empty (30b is not a level)", m.defaultReasoning)
		}
		_, _ = m.Complete(context.Background(), nil)
		if beta.lastModel != "qwen3:30b" {
			t.Errorf("model = %q, want %q", beta.lastModel, "qwen3:30b")
		}
	})

	t.Run("ollama-style tag with reasoning", func(t *testing.T) {
		r, _, beta := testRegistry(nil)
		m, err := r.Parse("beta/qwen3:30b:high")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m.defaultReasoning != ReasoningHigh {
			t.Errorf("reasoning = %q, want %q", m.defaultReasoning, ReasoningHigh)
		}
		_, _ = m.Complete(context.Background(), nil)
		if beta.lastModel != "qwen3:30b" {
			t.Errorf("model = %q, want %q", beta.lastModel, "qwen3:30b")
		}
	})

	t.Run("static alias", func(t *testing.T) {
		r, alpha, _ := testRegistry(nil)
		r.RegisterAlias("fast", "alpha/model-a")
		m, err := r.Parse("fast")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "model-a" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "model-a")
		}
	})

	t.Run("alias with embedded reasoning", func(t *testing.T) {
		r, alpha, _ := testRegistry(nil)
		r.RegisterAlias("thinking", "alpha/model-a:high")
		m, err := r.Parse("thinking")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m.defaultReasoning != ReasoningHigh {
			t.Errorf("reasoning = %q, want %q", m.defaultReasoning, ReasoningHigh)
		}
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "model-a" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "model-a")
		}
	})

	t.Run("user reasoning overrides alias default", func(t *testing.T) {
		r, _, _ := testRegistry(nil)
		r.RegisterAlias("thinking", "alpha/model-a:high")
		m, err := r.Parse("thinking:low")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m.defaultReasoning != ReasoningLow {
			t.Errorf("reasoning = %q, want %q (user override)", m.defaultReasoning, ReasoningLow)
		}
	})

	t.Run("dynamic resolver", func(t *testing.T) {
		r, alpha, _ := testRegistry(nil)
		r.RegisterResolver(ResolverFunc(func(name string) (string, ReasoningLevel, bool) {
			if name == "custom" {
				return "alpha/resolved-model", "", true
			}
			return "", "", false
		}))
		m, err := r.Parse("custom")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "resolved-model" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "resolved-model")
		}
	})

	t.Run("resolver with default reasoning", func(t *testing.T) {
		r, _, _ := testRegistry(nil)
		r.RegisterResolver(ResolverFunc(func(name string) (string, ReasoningLevel, bool) {
			if name == "smart" {
				return "alpha/model-a", ReasoningHigh, true
			}
			return "", "", false
		}))
		m, err := r.Parse("smart")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m.defaultReasoning != ReasoningHigh {
			t.Errorf("reasoning = %q, want %q", m.defaultReasoning, ReasoningHigh)
		}
	})

	t.Run("resolver default reasoning overridden by user", func(t *testing.T) {
		r, _, _ := testRegistry(nil)
		r.RegisterResolver(ResolverFunc(func(name string) (string, ReasoningLevel, bool) {
			if name == "smart" {
				return "alpha/model-a", ReasoningHigh, true
			}
			return "", "", false
		}))
		m, err := r.Parse("smart:low")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if m.defaultReasoning != ReasoningLow {
			t.Errorf("reasoning = %q, want %q (user override)", m.defaultReasoning, ReasoningLow)
		}
	})

	t.Run("resolver returns empty spec", func(t *testing.T) {
		r, _, _ := testRegistry(nil)
		r.RegisterResolver(ResolverFunc(func(name string) (string, ReasoningLevel, bool) {
			if name == "bad" {
				return "", "", true
			}
			return "", "", false
		}))
		_, err := r.Parse("bad")
		if err == nil {
			t.Fatal("expected error for empty resolver spec")
		}
	})

	t.Run("LLM_X env var with token", func(t *testing.T) {
		envFn := func(key string) string {
			if key == "LLM_M5" {
				return "alpha://mytoken@myhost.com"
			}
			return ""
		}
		r, alpha, _ := testRegistry(envFn)
		m, err := r.Parse("m5/qwen3:30b")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "qwen3:30b" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "qwen3:30b")
		}
	})

	t.Run("LLM_X env var without token", func(t *testing.T) {
		envFn := func(key string) string {
			if key == "LLM_LOCAL" {
				return "beta://localhost:11434"
			}
			return ""
		}
		r, _, beta := testRegistry(envFn)
		m, err := r.Parse("local/llama3.2")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if beta.lastModel != "llama3.2" {
			t.Errorf("model = %q, want %q", beta.lastModel, "llama3.2")
		}
	})

	t.Run("LLM_X with hyphenated name", func(t *testing.T) {
		envFn := func(key string) string {
			if key == "LLM_MY_BOX" {
				return "alpha://tok@host.com"
			}
			return ""
		}
		r, alpha, _ := testRegistry(envFn)
		m, err := r.Parse("my-box/some-model")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "some-model" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "some-model")
		}
	})

	t.Run("unknown provider no env var", func(t *testing.T) {
		r, _, _ := testRegistry(func(string) string { return "" })
		_, err := r.Parse("unknown/model")
		if err == nil {
			t.Fatal("expected error for unknown provider")
		}
		if !errors.Is(err, ErrUnknownProvider) {
			t.Errorf("error = %v, want ErrUnknownProvider", err)
		}
	})

	t.Run("bare unknown name no slash", func(t *testing.T) {
		r, _, _ := testRegistry(nil)
		_, err := r.Parse("nonexistent")
		if err == nil {
			t.Fatal("expected error for bare unknown name")
		}
		if !errors.Is(err, ErrUnknownProvider) {
			t.Errorf("error = %v, want ErrUnknownProvider", err)
		}
	})

	t.Run("alias loop", func(t *testing.T) {
		r, _, _ := testRegistry(nil)
		r.RegisterAlias("a", "b")
		r.RegisterAlias("b", "a")
		_, err := r.Parse("a")
		if err == nil {
			t.Fatal("expected error for alias loop")
		}
		if !errors.Is(err, ErrAliasLoop) {
			t.Errorf("error = %v, want ErrAliasLoop", err)
		}
	})

	t.Run("deep alias chain within limit", func(t *testing.T) {
		r, alpha, _ := testRegistry(nil)
		// chain: a0 → a1 → a2 → ... → a9 → alpha/model-a (depth 10 is fine, >10 is not)
		r.RegisterAlias("a9", "alpha/model-a")
		for i := 8; i >= 0; i-- {
			r.RegisterAlias(
				"a"+string(rune('0'+i)),
				"a"+string(rune('0'+i+1)),
			)
		}
		m, err := r.Parse("a0")
		if err != nil {
			t.Fatalf("unexpected error for deep but valid chain: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if alpha.lastModel != "model-a" {
			t.Errorf("model = %q, want %q", alpha.lastModel, "model-a")
		}
	})

	t.Run("RegisterProvider replaces existing", func(t *testing.T) {
		replaced := &recordingProvider{}
		r, _, _ := testRegistry(nil)
		r.RegisterProvider(ProviderInfo{
			Name:        "alpha",
			DisplayName: "Alpha Replaced",
			New: func(_ string, _ ...ClientOption) *Client {
				return NewClient(replaced)
			},
		})
		m, err := r.Parse("alpha/new-model")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if replaced.lastModel != "new-model" {
			t.Errorf("model = %q, want %q", replaced.lastModel, "new-model")
		}
		// Verify order is preserved (alpha is still at index 0).
		providers := r.Providers()
		if providers[0].Name != "alpha" {
			t.Errorf("first provider = %q, want %q (order preserved)", providers[0].Name, "alpha")
		}
		if providers[0].DisplayName != "Alpha Replaced" {
			t.Errorf("display name = %q, want %q", providers[0].DisplayName, "Alpha Replaced")
		}
	})

	t.Run("RegisterProvider adds new provider", func(t *testing.T) {
		gamma := &recordingProvider{}
		r, _, _ := testRegistry(nil)
		r.RegisterProvider(ProviderInfo{
			Name:        "gamma",
			DisplayName: "Gamma",
			New: func(_ string, _ ...ClientOption) *Client {
				return NewClient(gamma)
			},
		})
		m, err := r.Parse("gamma/g-model")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		_, _ = m.Complete(context.Background(), nil)
		if gamma.lastModel != "g-model" {
			t.Errorf("model = %q, want %q", gamma.lastModel, "g-model")
		}
		// New provider should be last.
		providers := r.Providers()
		last := providers[len(providers)-1]
		if last.Name != "gamma" {
			t.Errorf("last provider = %q, want %q", last.Name, "gamma")
		}
	})

	t.Run("DSN with unknown scheme", func(t *testing.T) {
		envFn := func(key string) string {
			if key == "LLM_X" {
				return "nope://tok@host.com"
			}
			return ""
		}
		r, _, _ := testRegistry(envFn)
		_, err := r.Parse("x/model")
		if err == nil {
			t.Fatal("expected error for unknown DSN scheme")
		}
		if !errors.Is(err, ErrUnknownProvider) {
			t.Errorf("error = %v, want ErrUnknownProvider", err)
		}
	})

	t.Run("DSN with invalid format", func(t *testing.T) {
		envFn := func(key string) string {
			if key == "LLM_BAD" {
				return "no-scheme"
			}
			return ""
		}
		r, _, _ := testRegistry(envFn)
		_, err := r.Parse("bad/model")
		if err == nil {
			t.Fatal("expected error for invalid DSN")
		}
		if !errors.Is(err, ErrInvalidDSN) {
			t.Errorf("error = %v, want ErrInvalidDSN", err)
		}
	})

	t.Run("createClient reads env key", func(t *testing.T) {
		var capturedKey string
		r, _, _ := testRegistry(func(key string) string {
			if key == "MY_KEY" {
				return "secret-123"
			}
			return ""
		})
		rec := &recordingProvider{}
		r.RegisterProvider(ProviderInfo{
			Name:   "keyed",
			EnvKey: "MY_KEY",
			New: func(apiKey string, opts ...ClientOption) *Client {
				capturedKey = apiKey
				return NewClient(rec)
			},
		})
		_, err := r.Parse("keyed/m")
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if capturedKey != "secret-123" {
			t.Errorf("apiKey = %q, want %q", capturedKey, "secret-123")
		}
	})
}

// ---------------------------------------------------------------------------
// Backward compatibility: package-level Providers() and ProviderByName()
// ---------------------------------------------------------------------------

func TestBackwardCompat(t *testing.T) {
	t.Run("Providers includes foreman", func(t *testing.T) {
		providers := Providers()
		found := false
		for _, p := range providers {
			if p.Name == "foreman" {
				found = true
				break
			}
		}
		if !found {
			t.Error("Providers() does not include foreman")
		}
	})

	t.Run("ProviderByName openai", func(t *testing.T) {
		p := ProviderByName("openai")
		if p == nil {
			t.Fatal("ProviderByName(\"openai\") returned nil")
		}
		if p.DisplayName != "OpenAI" {
			t.Errorf("DisplayName = %q, want %q", p.DisplayName, "OpenAI")
		}
	})

	t.Run("ProviderByName foreman", func(t *testing.T) {
		p := ProviderByName("foreman")
		if p == nil {
			t.Fatal("ProviderByName(\"foreman\") returned nil")
		}
		if p.DisplayName != "Foreman" {
			t.Errorf("DisplayName = %q, want %q", p.DisplayName, "Foreman")
		}
	})

	t.Run("ProviderByName unknown", func(t *testing.T) {
		p := ProviderByName("does-not-exist")
		if p != nil {
			t.Errorf("expected nil for unknown provider, got %+v", p)
		}
	})

	t.Run("Providers count", func(t *testing.T) {
		providers := Providers()
		// providerRegistry has 9 entries (openai, anthropic, google, deepseek,
		// moonshot, xai, groq, ollama, ollama-cloud) + foreman = 10
		if len(providers) < 10 {
			t.Errorf("len(Providers()) = %d, want >= 10", len(providers))
		}
	})
}

// ---------------------------------------------------------------------------
// NewRegistry isolation
// ---------------------------------------------------------------------------

func TestNewRegistryIsolation(t *testing.T) {
	r1 := NewRegistry()
	r2 := NewRegistry()

	r1.RegisterAlias("only-in-r1", "openai/gpt-4o")

	// r2 should not see r1's alias
	r2.mu.RLock()
	_, found := r2.aliases["only-in-r1"]
	r2.mu.RUnlock()
	if found {
		t.Error("alias registered in r1 should not appear in r2")
	}
}

// ---------------------------------------------------------------------------
// Comma-separated failover chains
// ---------------------------------------------------------------------------

func TestParse_CommaProducesFailover(t *testing.T) {
	resetHealthForTest()
	r, alpha, beta := testRegistry(func(string) string { return "" })

	m, err := r.Parse("alpha/model-a,beta/model-b")
	if err != nil {
		t.Fatalf("Parse failover spec: %v", err)
	}
	fp, ok := m.provider.(*failoverProvider)
	if !ok {
		t.Fatalf("expected *failoverProvider, got %T", m.provider)
	}
	if len(fp.entries) != 2 {
		t.Fatalf("expected 2 entries, got %d", len(fp.entries))
	}
	if fp.entries[0].specKey != "alpha/model-a" || fp.entries[1].specKey != "beta/model-b" {
		t.Errorf("unexpected specKeys: %q, %q", fp.entries[0].specKey, fp.entries[1].specKey)
	}
	// Complete routes to the first provider and passes the bare model name.
	_, err = m.Complete(context.Background(), []Message{{Role: RoleUser, Content: Content{Text: "hi"}}})
	if err != nil {
		t.Fatal(err)
	}
	if alpha.lastModel != "model-a" {
		t.Errorf("alpha got model %q, want model-a", alpha.lastModel)
	}
	if beta.lastModel != "" {
		t.Errorf("beta should not have been called, got model %q", beta.lastModel)
	}
}

func TestParse_NoCommaUnchanged(t *testing.T) {
	resetHealthForTest()
	r, _, _ := testRegistry(func(string) string { return "" })
	m, err := r.Parse("alpha/model-a")
	if err != nil {
		t.Fatal(err)
	}
	if _, ok := m.provider.(*failoverProvider); ok {
		t.Error("single (comma-free) spec must NOT produce a failover provider")
	}
}

func TestParse_CommaSinglePartFallsThrough(t *testing.T) {
	resetHealthForTest()
	r, _, _ := testRegistry(func(string) string { return "" })
	// Trailing comma / whitespace collapses to a single real part.
	m, err := r.Parse("alpha/model-a, ")
	if err != nil {
		t.Fatal(err)
	}
	if _, ok := m.provider.(*failoverProvider); ok {
		t.Error("a single effective part must not produce a failover provider")
	}
}

func TestParse_CommaFlattensNested(t *testing.T) {
	resetHealthForTest()
	r, _, _ := testRegistry(func(string) string { return "" })
	// Register an alias that is itself a comma chain.
	r.RegisterAlias("pair", "alpha/model-a,beta/model-b")
	m, err := r.Parse("pair,beta/model-b2")
	if err != nil {
		t.Fatal(err)
	}
	fp, ok := m.provider.(*failoverProvider)
	if !ok {
		t.Fatalf("expected *failoverProvider, got %T", m.provider)
	}
	if len(fp.entries) != 3 {
		t.Errorf("expected flattened 3 entries, got %d", len(fp.entries))
	}
}