feat: implement external genesis configuration support

[SIDDHANTCOOKIE]

Addressed Issues:

This PR fulfills the first requirement of Phase 1 (Week 3) of our roadmap by implementing externalized genesis configuration for MiniChain. Previously, the genesis block was hardcoded into chain.py with zero initial balances.
Now, MiniChain boots up by reading genesis.json. This gives us total control over the network's initial state without touching core logic.

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Summary by CodeRabbit

• New Features

  • Genesis configuration can be loaded from an external JSON file, including chain ID, timestamp, difficulty, and pre-funded accounts.

• Bug Fixes

  • Genesis validation now verifies the actual genesis block hash instead of assuming a fixed placeholder.

• Tests

  • Persistence tests updated to assert the restored genesis hash matches the saved chain.

• Chores

  • Initialization refactored to support configurable genesis loading.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

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📥 Commits

Reviewing files that changed from the base of the PR and between 310e564 and 568a521.

📒 Files selected for processing (4)

• genesis.json
• minichain/chain.py
• minichain/persistence.py
• tests/test_persistence.py

💤 Files with no reviewable changes (1)

• genesis.json

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Walkthrough

Adds a filesystem-backed genesis.json and refactors minichain/chain.py to load and apply genesis metadata and allocations; persistence now recomputes/verifies the genesis hash; tests updated to assert the computed genesis hash.

Changes

Genesis Block Configurability

Layer / File(s)	Summary
Genesis configuration file genesis.json	Defines chain_id, timestamp, difficulty, and alloc balances for pre-funded addresses.
Blockchain bootstrap and genesis creation minichain/chain.py	Adds json, os, sys imports; Blockchain.__init__ accepts genesis_path; _create_genesis_block loads JSON, applies alloc to State, sets timestamp/difficulty, computes genesis header hash, and optionally verifies/overrides with config["hash"].
Persistence genesis validation minichain/persistence.py	Replaces hard-coded zero-hash check by recomputing calculate_hash(genesis.to_header_dict()) and enforces genesis.index == 0.
Tests updated for computed genesis hash tests/test_persistence.py	Tests now compare restored genesis block hash against bc.chain[0].hash instead of expecting "0" * 64.

Sequence Diagram(s)

sequenceDiagram
  participant Blockchain
  participant OS
  participant JSON as JSONParser
  participant State
  Blockchain->>OS: read genesis_path file
  OS-->>JSON: file contents
  JSON-->>Blockchain: parsed genesis config
  Blockchain->>State: apply alloc balances
  Blockchain->>Blockchain: set timestamp and difficulty
  Blockchain->>Blockchain: calculate genesis header hash
  Blockchain->>Blockchain: verify or use configured hash

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• StabilityNexus/MiniChain#61: Related changes touching persistence and genesis validation logic.

Suggested labels

Python Lang

Suggested reviewers

• Zahnentferner

A genesis file hops into view, 🐰
Configured seeds in JSON laid true,
Balances sown, the header's cast anew,
Persistence checks the hash for proof,
A tiny chain wakes up, resilient and true.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: implement external genesis configuration support' accurately describes the main change—enabling external genesis configuration instead of hardcoded logic.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@minichain/chain.py`:
- Around line 52-56: The alloc loop in minichain/chain.py assigns balances from
external JSON without validation; update the loop that iterates over alloc
(where account = self.state.get_account(address) and account['balance'] = ...)
to validate each balance is an integer and non-negative before committing: parse
numeric strings safely (or reject non-numeric), ensure value >= 0, and either
raise a clear ValueError (or log and skip/normalize) when validation fails so
invalid balances are not written into state.
- Around line 44-50: The node currently continues startup with empty state when
genesis.json is missing or invalid; change the logic in chain.py around
genesis_path so that missing file or JSON parse errors cause a fail-fast exit:
if not os.path.exists(genesis_path) or json.load fails, log a clear error via
logger.error (including the exception/message) and terminate startup immediately
(e.g., raise SystemExit or call sys.exit(1)) instead of proceeding with a
default/empty config; update the block handling "with open(genesis_path...)" and
any surrounding code that assumes config to ensure startup is aborted on
load/parse failure.
- Around line 57-67: The code sets genesis_block.hash directly from config which
can create an inconsistent block; change the logic around the genesis Block
creation (the genesis_block assignment) to compute the canonical hash from the
genesis header (use the existing Block.calculate_hash or the module's
calculate_hash function) and then: if config contains a "hash", verify it equals
the computed hash and raise/log an error (or raise an exception) on mismatch; if
no "hash" present, assign the computed hash to genesis_block.hash. Ensure this
verification happens immediately after creating genesis_block and before
returning or persisting it.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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Configuration used: Path: .coderabbit.yaml

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📥 Commits

Reviewing files that changed from the base of the PR and between b08c967 and 310e564.

📒 Files selected for processing (2)

• genesis.json
• minichain/chain.py