package logz

import (
	"bytes"
	"context"
	"encoding/json"
	"log/slog"
	"strings"
	"testing"
)

// ---------------------------------------------------------------
// Duck-type test helpers
// ---------------------------------------------------------------

type errWithCode struct{ code string }

func (e *errWithCode) Error() string     { return e.code }
func (e *errWithCode) ErrorCode() string { return e.code }

type errWithCtx struct{ fields map[string]any }

func (e *errWithCtx) Error() string               { return "ctx-err" }
func (e *errWithCtx) ErrorContext() map[string]any { return e.fields }

type errFull struct {
	code   string
	fields map[string]any
}

func (e *errFull) Error() string               { return e.code }
func (e *errFull) ErrorCode() string           { return e.code }
func (e *errFull) ErrorContext() map[string]any { return e.fields }

// ---------------------------------------------------------------
// Helper: logger that writes to a buffer for inspection
// ---------------------------------------------------------------

func newTestLogger(buf *bytes.Buffer, level slog.Level) *slogLogger {
	handler := slog.NewJSONHandler(buf, &slog.HandlerOptions{Level: level})
	return &slogLogger{logger: slog.New(handler)}
}

// ---------------------------------------------------------------
// Constructor tests
// ---------------------------------------------------------------

func TestNew_ZeroOptions(t *testing.T) {
	logger := New(Options{})
	if logger == nil {
		t.Fatal("New(Options{}) returned nil")
	}
	// Zero value level is INFO — calling Info should not panic.
	logger.Info("zero options test")
}

func TestNew_JSONFormat(t *testing.T) {
	var buf bytes.Buffer
	sl := &slogLogger{
		logger: slog.New(slog.NewJSONHandler(&buf, &slog.HandlerOptions{Level: slog.LevelInfo})),
	}
	sl.Info("json test", "key", "value")

	var out map[string]any
	if err := json.Unmarshal(buf.Bytes(), &out); err != nil {
		t.Fatalf("expected JSON output, got: %s", buf.String())
	}
	if out["msg"] != "json test" {
		t.Errorf("unexpected msg: %v", out["msg"])
	}
}

func TestNew_StaticArgs(t *testing.T) {
	var buf bytes.Buffer
	handler := slog.NewJSONHandler(&buf, &slog.HandlerOptions{Level: slog.LevelInfo})
	base := slog.New(handler).With("service", "test-svc")
	sl := &slogLogger{logger: base}

	sl.Info("static args test")

	if !strings.Contains(buf.String(), "test-svc") {
		t.Errorf("static arg not found in output: %s", buf.String())
	}
}

// ---------------------------------------------------------------
// Logger method tests
// ---------------------------------------------------------------

func TestLogger_Debug_Info_Warn(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelDebug)

	// None of these should panic.
	l.Debug("debug msg")
	l.Info("info msg")
	l.Warn("warn msg")
}

func TestLogger_Error_StandardError(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelError)

	err := &errWithCode{code: "PLAIN"}
	l.Error("std error", err)

	if !strings.Contains(buf.String(), "std error") {
		t.Errorf("message not found in output: %s", buf.String())
	}
}

func TestLogger_Error_NilError(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelError)
	// Should not panic.
	l.Error("nil error test", nil)
}

func TestLogger_Error_DuckTypeCode(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelError)

	err := &errWithCode{code: "NOT_FOUND"}
	l.Error("duck code test", err)

	if !strings.Contains(buf.String(), "NOT_FOUND") {
		t.Errorf("error_code not found in output: %s", buf.String())
	}
}

func TestLogger_Error_DuckTypeContext(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelError)

	err := &errWithCtx{fields: map[string]any{"user_id": "abc"}}
	l.Error("duck ctx test", err)

	if !strings.Contains(buf.String(), "abc") {
		t.Errorf("context field not found in output: %s", buf.String())
	}
}

func TestLogger_Error_DuckTypeBoth(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelError)

	err := &errFull{code: "INTERNAL", fields: map[string]any{"op": "db.query"}}
	l.Error("full duck test", err)

	output := buf.String()
	if !strings.Contains(output, "INTERNAL") {
		t.Errorf("error_code not found in output: %s", output)
	}
	if !strings.Contains(output, "db.query") {
		t.Errorf("context field not found in output: %s", output)
	}
}

func TestLogger_With(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelInfo)

	child := l.With("component", "auth")
	child.Info("with test")

	if !strings.Contains(buf.String(), "auth") {
		t.Errorf("With attr not found in output: %s", buf.String())
	}

	// Original logger must not have the attribute.
	buf.Reset()
	l.Info("original")
	if strings.Contains(buf.String(), "auth") {
		t.Errorf("With mutated original logger: %s", buf.String())
	}
}

func TestLogger_WithContext_RequestID(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelInfo)

	ctx := WithRequestID(context.Background(), "req-123")
	child := l.WithContext(ctx)
	child.Info("ctx request id test")

	if !strings.Contains(buf.String(), "req-123") {
		t.Errorf("request_id not found in output: %s", buf.String())
	}
}

func TestLogger_WithContext_ExtraFields(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelInfo)

	ctx := WithField(context.Background(), "tenant", "acme")
	child := l.WithContext(ctx)
	child.Info("ctx fields test")

	if !strings.Contains(buf.String(), "acme") {
		t.Errorf("context field not found in output: %s", buf.String())
	}
}

func TestLogger_WithContext_EmptyContext(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelInfo)

	child := l.WithContext(context.Background())
	// Empty context — same pointer returned.
	if child != Logger(l) {
		t.Error("WithContext with empty context should return the same logger")
	}
}

func TestLogger_WithContext_NilContext(t *testing.T) {
	var buf bytes.Buffer
	l := newTestLogger(&buf, slog.LevelInfo)

	// Should not panic.
	child := l.WithContext(nil)
	if child != Logger(l) {
		t.Error("WithContext with nil context should return the same logger")
	}
}

// ---------------------------------------------------------------
// Context helper tests
// ---------------------------------------------------------------

func TestWithRequestID_GetRequestID(t *testing.T) {
	ctx := WithRequestID(context.Background(), "abc-123")
	if got := GetRequestID(ctx); got != "abc-123" {
		t.Errorf("GetRequestID = %q, want %q", got, "abc-123")
	}
}

func TestGetRequestID_NilContext(t *testing.T) {
	if got := GetRequestID(nil); got != "" {
		t.Errorf("GetRequestID(nil) = %q, want empty", got)
	}
}

func TestWithField(t *testing.T) {
	ctx := WithField(context.Background(), "key", "val")
	fields, ok := ctx.Value(ctxExtraFieldsKey{}).(map[string]any)
	if !ok {
		t.Fatal("no fields in context")
	}
	if fields["key"] != "val" {
		t.Errorf("field key = %v, want val", fields["key"])
	}
}

func TestWithFields(t *testing.T) {
	ctx := WithFields(context.Background(), map[string]any{"a": 1, "b": 2})
	fields, ok := ctx.Value(ctxExtraFieldsKey{}).(map[string]any)
	if !ok {
		t.Fatal("no fields in context")
	}
	if fields["a"] != 1 || fields["b"] != 2 {
		t.Errorf("fields = %v", fields)
	}
}

func TestWithFields_MergePreservesExisting(t *testing.T) {
	ctx := WithField(context.Background(), "first", "yes")
	ctx = WithFields(ctx, map[string]any{"second": "yes"})

	fields, _ := ctx.Value(ctxExtraFieldsKey{}).(map[string]any)
	if fields["first"] != "yes" {
		t.Error("first field was lost after second WithFields call")
	}
	if fields["second"] != "yes" {
		t.Error("second field not present after WithFields call")
	}
}

// ---------------------------------------------------------------
// enrichErrorAttrs tests
// ---------------------------------------------------------------

func TestEnrichErrorAttrs_NilError(t *testing.T) {
	attrs := []any{"existing", "value"}
	result := enrichErrorAttrs(nil, attrs)
	if len(result) != len(attrs) {
		t.Errorf("enrichErrorAttrs(nil) modified attrs: %v", result)
	}
}