1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

// ADAPTER PATTERN
// Goal: Make LegacyPrinter work with the DocumentPrinter interface
 
// The TARGET interface - what the client expects
interface DocumentPrinter {
    printDocument(content: string, format: 'A4' | 'Letter'): void;
}
 
// The ADAPTEE - existing class with incompatible interface
// This might be a third-party library or legacy code you can't modify
class LegacyPrinter {
    // Different method names, different parameters
    oldStylePrint(text: string, width: number, height: number): void {
        console.log(`Legacy printing: "${text}" at ${width}x${height}mm`);
    }
}
 
// The ADAPTER - wraps Adaptee to provide Target interface
class LegacyPrinterAdapter implements DocumentPrinter {
    private legacyPrinter: LegacyPrinter;
    
    constructor(legacyPrinter: LegacyPrinter) {
        this.legacyPrinter = legacyPrinter;
    }
    
    printDocument(content: string, format: 'A4' | 'Letter'): void {
        // ADAPT: Convert Target interface to Adaptee interface
        const dimensions = format === 'A4' 
            ? { width: 210, height: 297 } 
            : { width: 216, height: 279 };
        
        this.legacyPrinter.oldStylePrint(content, dimensions.width, dimensions.height);
    }
}
 
// Client code uses Target interface, unaware of Adaptee
function printReport(printer: DocumentPrinter, report: string): void {
    printer.printDocument(report, 'A4');
}
 
// Usage: Wrap legacy printer with adapter
const legacyPrinter = new LegacyPrinter();
const adaptedPrinter = new LegacyPrinterAdapter(legacyPrinter);
printReport(adaptedPrinter, "Quarterly Report");
 
// KEY CHARACTERISTICS:
// 1. Single hierarchy on the Adapter side (no Refined Abstractions)
// 2. Adaptee exists independently - we're wrapping, not designing
// 3. One-to-one relationship: one Adaptee, one Adapter
// 4. Focus: interface translation, not variation management

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110

// BRIDGE PATTERN
// Goal: Allow Documents and Printers to vary independently
 
// The IMPLEMENTOR - interface for implementation hierarchy
interface PrinterImplementor {
    // Primitive printing operations
    print(content: string, widthMm: number, heightMm: number): void;
    getPrinterName(): string;
}
 
// CONCRETE IMPLEMENTORS - different printing implementations
class LaserPrinterImpl implements PrinterImplementor {
    print(content: string, widthMm: number, heightMm: number): void {
        console.log(`[Laser] Printing "${content}" at ${widthMm}x${heightMm}mm`);
    }
    getPrinterName(): string { return "Laser Printer"; }
}
 
class InkjetPrinterImpl implements PrinterImplementor {
    print(content: string, widthMm: number, heightMm: number): void {
        console.log(`[Inkjet] Printing "${content}" at ${widthMm}x${heightMm}mm`);
    }
    getPrinterName(): string { return "Inkjet Printer"; }
}
 
class PdfPrinterImpl implements PrinterImplementor {
    print(content: string, widthMm: number, heightMm: number): void {
        console.log(`[PDF] Generating "${content}" as ${widthMm}x${heightMm}mm PDF`);
    }
    getPrinterName(): string { return "PDF Printer"; }
}
 
// The ABSTRACTION - document abstraction with reference to Implementor
abstract class Document {
    protected printer: PrinterImplementor;  // THE BRIDGE
    
    constructor(printer: PrinterImplementor) {
        this.printer = printer;
    }
    
    abstract print(): void;
}
 
// REFINED ABSTRACTIONS - different document types
class Report extends Document {
    constructor(
        printer: PrinterImplementor,
        private title: string,
        private content: string
    ) {
        super(printer);
    }
    
    print(): void {
        const formatted = `=== ${this.title} ===
${this.content}`;
        this.printer.print(formatted, 210, 297); // A4
    }
}
 
class Invoice extends Document {
    constructor(
        printer: PrinterImplementor,
        private invoiceNumber: string,
        private amount: number
    ) {
        super(printer);
    }
    
    print(): void {
        const formatted = `Invoice #${this.invoiceNumber}
Amount: $${this.amount}`;
        this.printer.print(formatted, 210, 297);
    }
}
 
class BusinessCard extends Document {
    constructor(
        printer: PrinterImplementor,
        private name: string,
        private title: string
    ) {
        super(printer);
    }
    
    print(): void {
        const formatted = `${this.name}
${this.title}`;
        this.printer.print(formatted, 85, 55); // Business card size
    }
}
 
// Usage: Any document type × Any printer type
const laser = new LaserPrinterImpl();
const inkjet = new InkjetPrinterImpl();
const pdf = new PdfPrinterImpl();
 
const reportOnLaser = new Report(laser, "Q4 Results", "Revenue increased...");
const invoiceOnPdf = new Invoice(pdf, "INV-001", 1500);
const cardOnInkjet = new BusinessCard(inkjet, "Jane Doe", "Senior Engineer");
 
reportOnLaser.print();
invoiceOnPdf.print();
cardOnInkjet.print();
 
// KEY CHARACTERISTICS:
// 1. TWO hierarchies: Document (Abstraction) and Printer (Implementor)
// 2. Both hierarchies designed together from the start
// 3. Many-to-many: Any abstraction can use any implementation
// 4. Focus: independent variation of two dimensions

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55

// Scenario: You're building a payment system
// Your code expects this interface:
interface PaymentProcessor {
    processPayment(amount: number, currency: string): Promise<PaymentResult>;
    refund(transactionId: string): Promise<RefundResult>;
}
 
// But you need to integrate Stripe, which has its own SDK:
// (You can't modify Stripe's code - it's a third-party library)
class Stripe {
    charges = {
        create: async (params: { amount: number; currency: string }) => {
            // Stripe's implementation
            return { id: 'ch_123', status: 'succeeded' };
        }
    };
    
    refunds = {
        create: async (params: { charge: string }) => {
            return { id: 're_123', status: 'succeeded' };
        }
    };
}
 
// ADAPTER: Wrap Stripe to match your interface
class StripePaymentAdapter implements PaymentProcessor {
    private stripe: Stripe;
    
    constructor(stripe: Stripe) {
        this.stripe = stripe;
    }
    
    async processPayment(amount: number, currency: string): Promise<PaymentResult> {
        // Adapt: Convert your interface to Stripe's interface
        const result = await this.stripe.charges.create({
            amount: amount * 100, // Stripe uses cents
            currency: currency.toLowerCase()
        });
        
        return {
            success: result.status === 'succeeded',
            transactionId: result.id
        };
    }
    
    async refund(transactionId: string): Promise<RefundResult> {
        const result = await this.stripe.refunds.create({ charge: transactionId });
        return { success: true, refundId: result.id };
    }
}
 
// Why Adapter and not Bridge?
// - Stripe already exists with a fixed interface
// - You're solving ONE integration problem
// - You're not designing for "payment processors × payment types" variation

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118

// Scenario: You're BUILDING a payment system from scratch
// You anticipate supporting multiple payment TYPES and multiple PROVIDERS
 
// IMPLEMENTOR: Provider implementation interface
interface PaymentProviderImpl {
    // Primitive operations that all providers must support
    charge(amountCents: number, currency: string, token: string): Promise<ProviderResult>;
    refundCharge(chargeId: string, amountCents: number): Promise<ProviderResult>;
    getProviderName(): string;
}
 
// CONCRETE IMPLEMENTORS: Different providers
class StripeProviderImpl implements PaymentProviderImpl {
    async charge(amountCents: number, currency: string, token: string): Promise<ProviderResult> {
        console.log(`Stripe: Charging ${amountCents} ${currency}`);
        return { success: true, externalId: 'ch_stripe_123' };
    }
    
    async refundCharge(chargeId: string, amountCents: number): Promise<ProviderResult> {
        return { success: true, externalId: 're_stripe_123' };
    }
    
    getProviderName(): string { return 'Stripe'; }
}
 
class PayPalProviderImpl implements PaymentProviderImpl {
    async charge(amountCents: number, currency: string, token: string): Promise<ProviderResult> {
        console.log(`PayPal: Charging ${amountCents} ${currency}`);
        return { success: true, externalId: 'pp_123' };
    }
    
    async refundCharge(chargeId: string, amountCents: number): Promise<ProviderResult> {
        return { success: true, externalId: 'pp_ref_123' };
    }
    
    getProviderName(): string { return 'PayPal'; }
}
 
// ABSTRACTION: Payment type abstraction
abstract class Payment {
    protected provider: PaymentProviderImpl; // THE BRIDGE
    
    constructor(provider: PaymentProviderImpl) {
        this.provider = provider;
    }
    
    abstract process(): Promise<PaymentResult>;
    abstract refund(): Promise<RefundResult>;
}
 
// REFINED ABSTRACTIONS: Different payment types
class OneTimePayment extends Payment {
    constructor(
        provider: PaymentProviderImpl,
        private amount: number,
        private currency: string,
        private paymentToken: string
    ) {
        super(provider);
    }
    
    private chargeId?: string;
    
    async process(): Promise<PaymentResult> {
        const result = await this.provider.charge(
            Math.round(this.amount * 100),
            this.currency,
            this.paymentToken
        );
        this.chargeId = result.externalId;
        return { success: result.success, transactionId: result.externalId };
    }
    
    async refund(): Promise<RefundResult> {
        if (!this.chargeId) throw new Error('No charge to refund');
        const result = await this.provider.refundCharge(
            this.chargeId,
            Math.round(this.amount * 100)
        );
        return { success: result.success, refundId: result.externalId };
    }
}
 
class SubscriptionPayment extends Payment {
    constructor(
        provider: PaymentProviderImpl,
        private monthlyAmount: number,
        private currency: string,
        private paymentToken: string
    ) {
        super(provider);
    }
    
    async process(): Promise<PaymentResult> {
        // Subscription-specific logic
        console.log(`Setting up monthly charge of ${this.monthlyAmount}`);
        const result = await this.provider.charge(
            Math.round(this.monthlyAmount * 100),
            this.currency,
            this.paymentToken
        );
        return { success: result.success, transactionId: result.externalId };
    }
    
    async refund(): Promise<RefundResult> {
        // Subscriptions might prorate refunds
        throw new Error('Use cancelSubscription() instead');
    }
}
 
// ANY payment type × ANY provider
const stripeOneTime = new OneTimePayment(new StripeProviderImpl(), 99.99, 'USD', 'tok_1');
const paypalSubscription = new SubscriptionPayment(new PayPalProviderImpl(), 9.99, 'USD', 'tok_2');
 
// Why Bridge and not Adapter?
// - You're DESIGNING both hierarchies from scratch
// - You anticipate MULTIPLE payment types AND MULTIPLE providers
// - Both sides will grow independently over time

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72

// ADAPTER: The Adapter knows EVERYTHING about the Adaptee
 
class XmlDataAdapter implements JsonDataSource {
    private xmlParser: LegacyXmlParser; // Adapter knows Adaptee intimately
    
    getData(): JsonObject {
        // Adapter knows exactly how the Adaptee works
        const xmlString = this.xmlParser.loadData();
        const xmlDoc = this.xmlParser.parseXml(xmlString);
        const elements = this.xmlParser.getElements(xmlDoc);
        
        // Complex conversion logic specific to this Adaptee
        return this.convertXmlElementsToJson(elements);
    }
    
    private convertXmlElementsToJson(elements: any[]): JsonObject {
        // Detailed knowledge of XML structure and quirks
    }
}
 
// The Adaptee knows NOTHING about the Adapter - it predates it
 
// ═══════════════════════════════════════════════════════════════════════════
 
// BRIDGE: The Abstraction knows only the Implementor INTERFACE
 
abstract class RemoteControl {
    protected device: Device; // Only knows interface, not concrete type
    
    constructor(device: Device) {
        this.device = device;
    }
    
    togglePower(): void {
        if (this.device.isEnabled()) {
            this.device.disable();
        } else {
            this.device.enable();
        }
    }
    
    // RemoteControl doesn't know if it's a TV, Radio, or SmartLight
    // It only knows the Device interface operations
}
 
// The Implementor knows NOTHING about the Abstraction
 
interface Device {
    isEnabled(): boolean;
    enable(): void;
    disable(): void;
    getVolume(): number;
    setVolume(percent: number): void;
}
 
class TV implements Device {
    // TV doesn't know it's being controlled by a RemoteControl
    // It just implements primitive operations
    private on: boolean = false;
    private volume: number = 50;
    
    isEnabled(): boolean { return this.on; }
    enable(): void { this.on = true; }
    disable(): void { this.on = false; }
    getVolume(): number { return this.volume; }
    setVolume(percent: number): void { this.volume = percent; }
}
 
// This bidirectional ignorance is intentional in Bridge:
// - Abstraction doesn't care which concrete Implementor it has
// - Implementor doesn't care which Abstraction is using it
// → Maximum decoupling and flexibility

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55

// WRONG: Creating adapters for every combination
// This is Adapter abuse - you're not adapting, you're designing
 
class MySqlUserRepositoryAdapter implements UserRepository {
    private mysql: MySqlConnection;
    async findUser(id: string): Promise<User> { /* ... */ }
}
 
class PostgresUserRepositoryAdapter implements UserRepository {
    private postgres: PostgresConnection;
    async findUser(id: string): Promise<User> { /* ... */ }
}
 
class MySqlOrderRepositoryAdapter implements OrderRepository {
    private mysql: MySqlConnection;
    async findOrder(id: string): Promise<Order> { /* ... */ }
}
 
class PostgresOrderRepositoryAdapter implements OrderRepository {
    private postgres: PostgresConnection;
    async findOrder(id: string): Promise<Order> { /* ... */ }
}
 
// 4 adapters for 2 × 2... this will explode
 
// CORRECT: Use Bridge pattern
interface DatabaseConnection {  // Implementor
    query(sql: string, params: any[]): Promise<any[]>;
    execute(sql: string, params: any[]): Promise<void>;
}
 
class MySqlConnection implements DatabaseConnection { /* ... */ }
class PostgresConnection implements DatabaseConnection { /* ... */ }
 
abstract class Repository {  // Abstraction
    protected db: DatabaseConnection;
    constructor(db: DatabaseConnection) { this.db = db; }
}
 
class UserRepository extends Repository {
    async findUser(id: string): Promise<User> {
        const rows = await this.db.query('SELECT * FROM users WHERE id = ?', [id]);
        return this.mapToUser(rows[0]);
    }
}
 
class OrderRepository extends Repository {
    async findOrder(id: string): Promise<Order> {
        const rows = await this.db.query('SELECT * FROM orders WHERE id = ?', [id]);
        return this.mapToOrder(rows[0]);
    }
}
 
// 2 + 2 = 4 classes instead of 2 × 2 = 4... but with 5 repos and 3 DBs:
// Bridge: 5 + 3 = 8 vs Adapter abuse: 5 × 3 = 15

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48

// WRONG: Overengineering for a simple integration
// You just need to wrap one analytics library, that's it
 
// Unnecessary abstraction hierarchy
abstract class AnalyticsEvent {
    protected impl: AnalyticsImplementor;
    constructor(impl: AnalyticsImplementor) { this.impl = impl; }
    abstract track(): void;
}
 
class PageViewEvent extends AnalyticsEvent {
    track(): void { /* ... */ }
}
 
class ClickEvent extends AnalyticsEvent {
    track(): void { /* ... */ }
}
 
interface AnalyticsImplementor {
    sendEvent(name: string, properties: object): void;
}
 
class GoogleAnalyticsImpl implements AnalyticsImplementor {
    sendEvent(name: string, properties: object): void { /* ... */ }
}
 
// This is Bridge overkill for: "I need to use Google Analytics in my app"
 
// CORRECT: Simple Adapter is enough
interface Analytics {
    trackPageView(page: string): void;
    trackClick(element: string): void;
}
 
class GoogleAnalyticsAdapter implements Analytics {
    private ga: GoogleAnalyticsSDK;
    
    trackPageView(page: string): void {
        this.ga.send('pageview', { page });
    }
    
    trackClick(element: string): void {
        this.ga.send('event', { action: 'click', label: element });
    }
}
 
// Clean and simple. If you later need Mixpanel, add MixpanelAdapter.
// Don't over-architect until you actually have multiple dimensions of variation.

                    ┌──────────────────────────────────┐
                    │ Do you have an EXISTING interface│
                    │ that needs to work with your code│
                    │ (third-party, legacy, external)? │
                    └───────────────┬──────────────────┘
                                    │
                    ┌───────────────┴───────────────┐
                    │                               │
                    ▼                               ▼
                   YES                              NO
                    │                               │
        ┌───────────┴───────────┐       ┌──────────┴──────────┐
        │ Can you modify the    │       │ Are you designing a │
        │ existing code?        │       │ new system with TWO+ │
        │                       │       │ dimensions of        │
        │                       │       │ variation?           │
        └───────────┬───────────┘       └──────────┬──────────┘
                    │                               │
        ┌───────────┴───────────┐       ┌──────────┴──────────┐
        │                       │       │                      │
        ▼                       ▼       ▼                      ▼
       YES                      NO     YES                     NO
        │                       │       │                      │
        ▼                       ▼       ▼                      ▼
┌───────────────┐       ┌───────────┐ ┌───────────┐    ┌───────────────┐
│ Consider      │       │           │ │           │    │ Start simple  │
│ refactoring   │       │  ADAPTER  │ │  BRIDGE   │    │ Single class  │
│ to common     │       │           │ │           │    │ or interface  │
│ interface     │       │           │ │           │    │               │
└───────────────┘       └───────────┘ └───────────┘    └───────────────┘
 
 
ADDITIONAL QUESTIONS:
 
┌─────────────────────────────────────────────────────────────────────────────┐
│ QUESTION                                           │ YES → BRIDGE │ NO → ?  │
├────────────────────────────────────────────────────┼──────────────┼─────────┤
│ Will abstraction variants grow over time?          │      ✓       │ Adapter │
│ Will implementation variants grow over time?       │      ✓       │ Adapter │
│ Do you need runtime switching of implementation?   │      ✓       │ Adapter │
│ Are you integrating ONE third-party library?       │   Adapter    │    ✓    │
│ Is the interface mismatch your only problem?       │   Adapter    │    ✓    │
└─────────────────────────────────────────────────────────────────────────────┘

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179

// SCENARIO: Building a multi-cloud storage system
// - Multiple storage ABSTRACTIONS (File, Block, Object)
// - Multiple IMPLEMENTATIONS (AWS, Azure, GCP)
// - Some implementations are third-party SDKs that need adapting
 
// ═══════════════════════════════════════════════════════════════════════════
// BRIDGE PATTERN: Overall architecture
// ═══════════════════════════════════════════════════════════════════════════
 
// IMPLEMENTOR: Our storage operations interface
interface StorageImplementor {
    upload(key: string, data: Buffer): Promise<string>;
    download(key: string): Promise<Buffer>;
    delete(key: string): Promise<void>;
    list(prefix: string): Promise<string[]>;
}
 
// ABSTRACTION: Storage abstraction hierarchy
abstract class Storage {
    protected impl: StorageImplementor;  // BRIDGE
    
    constructor(impl: StorageImplementor) {
        this.impl = impl;
    }
    
    abstract store(item: any): Promise<string>;
    abstract retrieve(id: string): Promise<any>;
}
 
// REFINED ABSTRACTIONS
class FileStorage extends Storage {
    async store(file: { name: string; content: Buffer }): Promise<string> {
        return this.impl.upload(`files/${file.name}`, file.content);
    }
    
    async retrieve(fileName: string): Promise<{ name: string; content: Buffer }> {
        const content = await this.impl.download(`files/${fileName}`);
        return { name: fileName, content };
    }
}
 
class DocumentStorage extends Storage {
    async store(doc: { id: string; data: object }): Promise<string> {
        const json = JSON.stringify(doc.data);
        return this.impl.upload(`docs/${doc.id}.json`, Buffer.from(json));
    }
    
    async retrieve(docId: string): Promise<{ id: string; data: object }> {
        const content = await this.impl.download(`docs/${docId}.json`);
        return { id: docId, data: JSON.parse(content.toString()) };
    }
}
 
// ═══════════════════════════════════════════════════════════════════════════
// ADAPTER PATTERN: Integrating third-party SDKs into our Implementor hierarchy
// ═══════════════════════════════════════════════════════════════════════════
 
// Third-party AWS SDK (can't modify)
class AWSS3Client {
    async putObject(bucket: string, key: string, body: Buffer): Promise<{ ETag: string }> {
        console.log(`[AWS S3] Uploading to ${bucket}/${key}`);
        return { ETag: 'etag123' };
    }
    
    async getObject(bucket: string, key: string): Promise<{ Body: Buffer }> {
        console.log(`[AWS S3] Downloading ${bucket}/${key}`);
        return { Body: Buffer.from('content') };
    }
    
    async deleteObject(bucket: string, key: string): Promise<void> {
        console.log(`[AWS S3] Deleting ${bucket}/${key}`);
    }
    
    async listObjectsV2(bucket: string, prefix: string): Promise<{ Contents: { Key: string }[] }> {
        return { Contents: [{ Key: 'file1' }, { Key: 'file2' }] };
    }
}
 
// ADAPTER: Adapts AWS SDK to our StorageImplementor interface
class AWSS3Adapter implements StorageImplementor {
    private s3: AWSS3Client;
    private bucket: string;
    
    constructor(s3: AWSS3Client, bucket: string) {
        this.s3 = s3;
        this.bucket = bucket;
    }
    
    async upload(key: string, data: Buffer): Promise<string> {
        const result = await this.s3.putObject(this.bucket, key, data);
        return result.ETag;
    }
    
    async download(key: string): Promise<Buffer> {
        const result = await this.s3.getObject(this.bucket, key);
        return result.Body;
    }
    
    async delete(key: string): Promise<void> {
        await this.s3.deleteObject(this.bucket, key);
    }
    
    async list(prefix: string): Promise<string[]> {
        const result = await this.s3.listObjectsV2(this.bucket, prefix);
        return result.Contents.map(c => c.Key);
    }
}
 
// Third-party Azure SDK (can't modify)
class AzureBlobClient {
    async uploadBlob(container: string, blobName: string, content: Buffer): Promise<string> {
        console.log(`[Azure Blob] Uploading to ${container}/${blobName}`);
        return 'azure-url';
    }
    
    async downloadBlob(container: string, blobName: string): Promise<Buffer> {
        return Buffer.from('azure content');
    }
    
    async deleteBlob(container: string, blobName: string): Promise<void> { }
    
    async listBlobs(container: string, prefix: string): Promise<string[]> {
        return ['blob1', 'blob2'];
    }
}
 
// ADAPTER: Adapts Azure SDK to our StorageImplementor interface
class AzureBlobAdapter implements StorageImplementor {
    private azure: AzureBlobClient;
    private container: string;
    
    constructor(azure: AzureBlobClient, container: string) {
        this.azure = azure;
        this.container = container;
    }
    
    async upload(key: string, data: Buffer): Promise<string> {
        return this.azure.uploadBlob(this.container, key, data);
    }
    
    async download(key: string): Promise<Buffer> {
        return this.azure.downloadBlob(this.container, key);
    }
    
    async delete(key: string): Promise<void> {
        await this.azure.deleteBlob(this.container, key);
    }
    
    async list(prefix: string): Promise<string[]> {
        return this.azure.listBlobs(this.container, prefix);
    }
}
 
// ═══════════════════════════════════════════════════════════════════════════
// USAGE: Bridge structure with Adapted implementations
// ═══════════════════════════════════════════════════════════════════════════
 
// Create adapters for each cloud provider
const awsAdapter = new AWSS3Adapter(new AWSS3Client(), 'my-bucket');
const azureAdapter = new AzureBlobAdapter(new AzureBlobClient(), 'my-container');
 
// Bridge: Any abstraction × Any adapted implementation
const awsFileStorage = new FileStorage(awsAdapter);
const azureDocStorage = new DocumentStorage(azureAdapter);
const awsDocStorage = new DocumentStorage(awsAdapter);
 
// All combinations work!
await awsFileStorage.store({ name: 'report.pdf', content: Buffer.from('...') });
await azureDocStorage.store({ id: 'doc1', data: { title: 'Hello' } });
await awsDocStorage.retrieve('doc2');
 
// STRUCTURE SUMMARY:
// └── Bridge Pattern (overall architecture)
//     ├── Abstraction: Storage
//     │   ├── Refined: FileStorage
//     │   └── Refined: DocumentStorage
//     └── Implementor: StorageImplementor
//         ├── Adapter: AWSS3Adapter (wraps AWSS3Client)
//         └── Adapter: AzureBlobAdapter (wraps AzureBlobClient)