feat: Add Proof of Work implementation for v2

[Perafan18]

Summary

• Implements Proof of Work (PoW) mining algorithm for blocks
• Adds nonce and difficulty fields to Block model
• Implements mine_block method that finds valid hash with required leading zeros
• Updates block creation to mine blocks before saving
• Adds validation to check PoW difficulty requirement
• Adds GET endpoint to retrieve block details including mining information

Technical Details

• Mining Algorithm: Increments nonce until hash starts with required number of zeros
• Default Difficulty: 2 (requires 2 leading zeros in hash)
• Configurable: Difficulty can be specified when creating blocks
• Validation: valid_hash? method checks if hash meets difficulty requirement
• Blockchain Integrity: Updated to validate PoW for all blocks

API Changes

• POST /chain/:id/block: Now accepts optional difficulty parameter and returns nonce and difficulty in response
• GET /chain/:id/block/:block_id: New endpoint to retrieve complete block details including mining information

Test plan

• Test block mining with default difficulty (2)
• Test block mining with custom difficulty
• Verify mined blocks have required leading zeros in hash
• Test blockchain integrity validation with PoW
• Test GET endpoint for block details
• Verify nonce increments until valid hash is found

🤖 Generated with Claude Code

Summary by CodeRabbit

• Nuevas funcionalidades

  • Minado Proof-of-Work integrado con dificultad configurable y campos públicos nonce y dificultad.
  • Nueva API para recuperar bloques individuales por identificador; respuestas incluyen datos completos del bloque (hash, nonce, dificultad, timestamp, etc.).

• Mejoras

  • Validación de integridad reforzada y respuesta de creación de bloque ampliada con nonce y dificultad.

[coderabbitai]

Walkthrough

Se introduce Proof-of-Work: Block ahora tiene campos nonce y difficulty, incluye minería (mine_block) y validación de hash (valid_hash?). Blockchain#add_block acepta difficulty: y mina antes de guardar. API: POST /chain/:id/block devuelve nonce y difficulty; añadido GET /chain/:id/block/:block_id.

Cambios

Cohort / File(s)	Resumen
API / Aplicación main.rb	Añadido endpoint GET '/chain/:id/block/:block_id' para recuperar un bloque completo. POST '/chain/:id/block' ahora valida difficulty, invoca blockchain.add_block(..., difficulty: difficulty) y devuelve block_hash, nonce y difficulty. Añadido helper validate_difficulty.
Modelo: Block src/block.rb	Añadidos campos públicos nonce (Integer, default 0) y difficulty (Integer, default 2). calculate_hash incorpora nonce. Nuevo método mine_block que itera nonce hasta cumplir la dificultad; nuevo método valid_hash? para verificar el hash contra la dificultad. Validaciones actualizadas.
Modelo: Blockchain src/blockchain.rb	Firma de add_block cambiada a add_block(data, difficulty: 2). Construye bloque con difficulty, llama mine_block, guarda (save!) y retorna. integrity_valid? ahora incluye comprobación current_block.valid_hash?.

Diagramas de Secuencia

sequenceDiagram
    participant Cliente
    participant App as main.rb
    participant Blockchain
    participant Block

    Cliente->>App: POST /chain/:id/block (data, difficulty)
    App->>App: validate_difficulty(difficulty)
    App->>Blockchain: add_block(data, difficulty)
    Blockchain->>Block: build new block(data, difficulty)
    Block-->Block: nonce = 0
    Blockchain->>Block: mine_block()
    loop Minado (PoW)
        Block->>Block: incrementar nonce
        Block->>Block: calcular hash
        alt hash cumple dificultad
            Block-->>Blockchain: hash minado
        end
    end
    Blockchain->>Blockchain: save! block
    Blockchain-->>App: bloque creado
    App-->>Cliente: { block_hash, nonce, difficulty }

    Cliente->>App: GET /chain/:id/block/:block_id
    App->>Blockchain: find_block(block_id)
    Blockchain-->>App: bloque
    App->>Block: valid_hash?
    Block-->>App: true/false
    App-->>Cliente: { id, index, data, hash, previous_hash, nonce, difficulty, timestamp, valid_hash }

Loading

Esfuerzo estimado de revisión de código

🎯 4 (Complejo) | ⏱️ ~45 minutos

• Revisar comportamiento de mine_block por riesgo de bucles largos/infinitos si difficulty es alto.
• Comprobar que calculate_hash y valid_hash? usan exactamente los mismos campos (consistencia).
• Verificar migración de add_block en llamadas existentes y manejo de errores en validate_difficulty.
• Asegurar que respuestas JSON y tests (si existen) se actualizan para los nuevos campos nonce y difficulty.

Poema

🐰 Con patas blandas y ojos curiosos,
cuento nonces que saltan y giran en paz,
la cadena late en ritmos laboriosos,
ceros al frente: el misterio verás.
¡Minería y canto, un bloque más!

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	El título describe con precisión la característica principal del cambio: la implementación de Proof of Work (PoW) para la versión 2, que es el objetivo central del PR.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feature/v2-proof-of-work

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📜 Recent review details

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Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1e49e45 and 0335861.

📒 Files selected for processing (1)

• main.rb (3 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• main.rb

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Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 59c87f0 and 1e49e45.

📒 Files selected for processing (3)

• main.rb (2 hunks)
• src/block.rb (2 hunks)
• src/blockchain.rb (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (2)

src/blockchain.rb (1)

src/block.rb (3)

• mine_block (60-69)
• calculate_hash (43-46)
• valid_hash? (74-77)

main.rb (2)

src/blockchain.rb (1)

• add_block (22-34)

src/block.rb (1)

• valid_hash? (74-77)