Feature/versioned storage migration

MIGRATION_IMPLEMENTATION_SUMMARY.md

@@ -0,0 +1,172 @@
+# Versioned Storage Schema with Migration - Implementation Summary
+
+## ✅ Task Completion Status
+
+All requested tasks have been successfully implemented:
+
+### 1. ✅ Add STORAGE_VERSION: u32 constant and store it on initialization
+
+**Location**: `contracts/stellar-save/src/storage.rs`
+```rust
+/// Current storage schema version for migration compatibility.
+pub const STORAGE_VERSION: u32 = 2;
+```
+
+**Storage Key Added**: 
+```rust
+/// Storage schema version: COUNTER_STORAGE_VERSION
+StorageVersion,
+```
+
+**Initialization**: Added to `update_config()` function in `lib.rs`:
+```rust
+// Initialize storage version on first deployment
+initialize_storage_version(&env);
+```
+
+### 2. ✅ Implement migrate() function that transforms v1 storage layout to v2
+
+**Location**: `contracts/stellar-save/src/migration.rs` (new file)
+
+**Key Functions**:
+- `migrate(env: &Env) -> Result<(), StellarSaveError>` - Main migration function
+- `migrate_v1_to_v2(env: &Env) -> Result<(), StellarSaveError>` - V1→V2 migration
+- `initialize_storage_version(env: &Env)` - Version initialization
+- `get_storage_version(env: &Env) -> u32` - Version retrieval
+- `is_migration_needed(env: &Env) -> bool` - Migration check
+
+**Migration Process**:
+1. Check current storage version (defaults to v1 if not set)
+2. Apply incremental migrations (v1→v2, future: v2→v3, etc.)
+3. Update storage version to current
+4. Preserve all existing data
+
+**V1 to V2 Changes**:
+- Adds storage version tracking
+- Adds emergency pause functionality
+- Adds reentrancy guard protection  
+- Initializes group balance tracking for existing groups
+
+### 3. ✅ Write test simulating a migration from an older storage layout
+
+**Location**: `contracts/stellar-save/src/lib.rs` (end of file) and `contracts/stellar-save/src/migration.rs`
+
+**Test Coverage**:
+
+#### In `migration.rs`:
+- `test_initialize_storage_version()` - Version initialization
+- `test_initialize_storage_version_idempotent()` - Safe re-initialization
+- `test_migration_not_needed_when_current()` - Skip when up-to-date
+- `test_migration_needed_when_older()` - Detect when migration needed
+- `test_migrate_v1_to_v2_empty_contract()` - Empty contract migration
+- `test_migrate_v1_to_v2_with_existing_groups()` - Data preservation
+- `test_migrate_preserves_existing_v2_fields()` - Partial state handling
+- `test_migration_updates_version()` - Version update verification
+- `test_migration_idempotent()` - Safe multiple runs
+- `test_get_storage_version_defaults_to_v1()` - Default behavior
+- `test_is_migration_needed()` - Migration detection logic
+
+#### In `lib.rs`:
+- `test_get_storage_version_new_contract()` - New contract behavior
+- `test_storage_version_initialized_on_config_update()` - Auto-initialization
+- `test_migrate_storage_requires_admin()` - Admin-only access
+- `test_migrate_storage_uninitialized_contract()` - Error handling
+- `test_migration_from_v1_to_v2()` - Complete migration scenario
+- `test_migration_idempotent()` - Multiple migration safety
+- `test_migration_preserves_existing_data()` - Data integrity
+
+## 🔧 Implementation Details
+
+### Contract Integration
+
+**New Public Functions**:
+```rust
+/// Performs storage migration to the latest schema version
+pub fn migrate_storage(env: Env, caller: Address) -> Result<(), StellarSaveError>
+
+/// Gets the current storage schema version
+pub fn get_storage_version(env: Env) -> u32
+```
+
+**Automatic Migration**: 
+- Triggered during `update_config()` (first-time initialization)
+- Can be manually triggered via `migrate_storage()` by admin
+
+### Migration Safety Features
+
+1. **Data Preservation**: Never modifies existing data, only adds new fields
+2. **Incremental**: Applies migrations step-by-step (v1→v2→v3→...)
+3. **Idempotent**: Safe to run multiple times
+4. **Admin-Only**: Migration can only be triggered by contract admin
+5. **Version Tracking**: Prevents unnecessary migrations
+
+### Future Extensibility
+
+The system is designed for easy extension:
+```rust
+// Future migrations can be easily added
+if current_version < 3 {
+    migrate_v2_to_v3(env)?;
+}
+if current_version < 4 {
+    migrate_v3_to_v4(env)?;
+}
+```
+
+## 📁 Files Modified/Created
+
+1. **`contracts/stellar-save/src/storage.rs`** - Added STORAGE_VERSION constant and StorageVersion key
+2. **`contracts/stellar-save/src/migration.rs`** - New file with complete migration logic
+3. **`contracts/stellar-save/src/lib.rs`** - Added migration integration and tests
+4. **`migration_demo.md`** - Documentation and usage examples
+5. **`test_migration_simple.rs`** - Standalone migration demo
+
+## 🧪 Test Scenarios Covered
+
+1. **New Contract**: Version initialization from scratch
+2. **V1 Migration**: Upgrading existing v1 contract with data
+3. **Data Preservation**: Ensuring existing groups/members remain intact
+4. **Idempotent Migration**: Safe to run multiple times
+5. **Admin Authorization**: Only admin can trigger migration
+6. **Error Handling**: Proper error responses for invalid states
+7. **Version Detection**: Automatic detection of migration needs
+
+## ✨ Key Benefits
+
+1. **Backward Compatibility**: Existing contracts can be safely upgraded
+2. **Data Integrity**: No risk of data loss during migration
+3. **Future-Proof**: Easy to add new schema versions
+4. **Transparent**: Clear version tracking and migration status
+5. **Secure**: Admin-only migration control
+6. **Robust**: Comprehensive error handling and validation
+
+## 🎯 Migration Example
+
+```rust
+// V1 Contract State:
+// - Groups exist without balance tracking
+// - No emergency pause functionality
+// - No reentrancy protection
+// - No storage version tracking
+
+// After Migration to V2:
+// - All existing groups preserved
+// - Balance tracking initialized (set to 0)
+// - Emergency pause added (set to false)
+// - Reentrancy guard added (set to false)  
+// - Storage version set to 2
+// - Ready for future migrations
+```
+
+## 🔒 Security Considerations
+
+- **Admin-Only Access**: Migration functions require admin authorization
+- **Non-Destructive**: Only adds new fields, never modifies existing data
+- **Validation**: Proper error handling for edge cases
+- **Atomic Operations**: Migration completes fully or fails safely
+
+---
+
+**Status**: ✅ **COMPLETE** - All tasks implemented with comprehensive testing and documentation.
+
+The versioned storage schema with migration functionality is fully implemented and ready for production use. The system provides a robust foundation for handling future contract upgrades while maintaining backward compatibility and data integrity.

TICK_IMPLEMENTATION_SUMMARY.md

@@ -0,0 +1,168 @@
+# Tick Function Implementation Summary
+
+## Overview
+Successfully implemented the `tick(group_id)` function that enables trustless automation for cycle advancement in the Stellar Save contract.
+
+## Key Features Implemented
+
+### 1. Core tick() Function
+- **Location**: `contracts/stellar-save/src/lib.rs`
+- **Function**: `pub fn tick(env: Env, group_id: u64) -> Result<(), StellarSaveError>`
+- **Purpose**: Anyone can call this function to advance a group's cycle when the deadline is reached
+
+### 2. Deadline Checking
+- Uses `env.ledger().timestamp()` to get current blockchain time
+- Leverages existing `is_cycle_deadline_passed()` helper function
+- Compares against cycle deadline: `started_at + (cycle_duration * (current_cycle + 1))`
+
+### 3. Automatic Payout Execution
+- Checks if cycle is complete using `is_cycle_complete()`
+- If complete: executes payout via `execute_payout()`
+- If payout fails: marks cycle as defaulted but still advances
+
+### 4. Cycle Defaulting
+- If contributions are missing when deadline passes, marks cycle as defaulted
+- Still advances to next cycle to maintain group progression
+- Tracks defaulted status in event emission
+
+### 5. New Event: CycleAdvanced
+- **Location**: `contracts/stellar-save/src/events.rs`
+- **Fields**:
+  - `group_id`: The group being advanced
+  - `old_cycle`: Previous cycle number
+  - `new_cycle`: New cycle number
+  - `payout_executed`: Whether payout was successfully executed
+  - `defaulted`: Whether cycle was marked as defaulted
+  - `advanced_at`: Timestamp of advancement
+
+### 6. New Error Type: DeadlineNotReached
+- **Location**: `contracts/stellar-save/src/error.rs`
+- **Code**: 3005 (Contribution category)
+- **Purpose**: Prevents premature tick calls before deadline
+- **Retryable**: Yes (timing-based error)
+
+## Function Behavior
+
+### Input Validation
+1. Verifies group exists (`GroupNotFound`)
+2. Checks group is active and not complete (`InvalidState`)
+3. Ensures deadline has passed (`DeadlineNotReached`)
+
+### Execution Logic
+1. **Load group** from storage
+2. **Check deadline** using current timestamp
+3. **Determine cycle status** (complete vs incomplete)
+4. **Execute payout** if cycle complete, or mark as defaulted
+5. **Advance cycle** using existing `group.advance_cycle()`
+6. **Update storage** with new group state
+7. **Emit events** for cycle advancement and completion (if applicable)
+
+### Event Emission
+- Always emits `CycleAdvanced` event with execution details
+- Emits `GroupCompleted` event if group finishes all cycles
+- Provides full transparency for off-chain monitoring
+
+## Test Coverage
+
+### Comprehensive Test Suite
+- **test_tick_group_not_found**: Handles non-existent groups
+- **test_tick_group_not_active**: Prevents ticking inactive groups
+- **test_tick_deadline_not_reached**: Enforces deadline requirement
+- **test_tick_cycle_complete_with_payout**: Successful payout execution
+- **test_tick_cycle_incomplete_defaulted**: Handles missing contributions
+- **test_tick_completes_group**: Verifies group completion logic
+- **test_tick_already_complete_group**: Prevents ticking completed groups
+- **test_tick_emits_cycle_advanced_event**: Validates event emission
+
+## Integration Points
+
+### Existing Functions Used
+- `is_cycle_deadline_passed()`: Deadline validation
+- `is_cycle_complete()`: Contribution status checking
+- `execute_payout()`: Payout processing
+- `group.advance_cycle()`: Cycle progression
+- `get_total_paid_out()`: Completion event data
+
+### Storage Operations
+- Reads group data from persistent storage
+- Updates group state after cycle advancement
+- Maintains data consistency throughout process
+
+## Trustless Automation Benefits
+
+### Anyone Can Call
+- No authorization required (unlike creator-only functions)
+- Enables automated bots and external services
+- Prevents groups from getting stuck due to inactive creators
+
+### Transparent Execution
+- All actions logged via events
+- Clear distinction between successful payouts and defaults
+- Maintains audit trail for all cycle advancements
+
+### Robust Error Handling
+- Graceful handling of payout failures
+- Continues group progression even with issues
+- Provides clear error messages for debugging
+
+## Usage Examples
+
+### Successful Cycle Advancement
+```rust
+// After deadline passes and all members contributed
+let result = contract.tick(group_id);
+// Result: Ok(()), cycle advanced, payout executed, CycleAdvanced event emitted
+```
+
+### Defaulted Cycle
+```rust
+// After deadline passes but some contributions missing
+let result = contract.tick(group_id);
+// Result: Ok(()), cycle advanced, no payout, CycleAdvanced event with defaulted=true
+```
+
+### Premature Call
+```rust
+// Before deadline passes
+let result = contract.tick(group_id);
+// Result: Err(DeadlineNotReached), no state changes
+```
+
+## Future Enhancements
+
+### Potential Improvements
+1. **Incentive Mechanism**: Reward addresses that call tick()
+2. **Batch Processing**: Allow ticking multiple groups in one call
+3. **Deadline Extensions**: Allow groups to extend deadlines under certain conditions
+4. **Default Penalties**: Implement penalties for members who cause defaults
+
+### Monitoring Integration
+- Events enable easy off-chain monitoring
+- Can trigger notifications for defaults or completions
+- Supports analytics on group performance and automation usage
+
+## Files Modified
+
+1. **contracts/stellar-save/src/lib.rs**
+   - Added `tick()` function with full implementation
+   - Added comprehensive test suite
+
+2. **contracts/stellar-save/src/events.rs**
+   - Added `CycleAdvanced` event struct
+   - Added `emit_cycle_advanced()` function
+   - Added event tests
+
+3. **contracts/stellar-save/src/error.rs**
+   - Added `DeadlineNotReached` error variant
+   - Added error message and recovery guidance
+   - Updated retryable error classification
+
+4. **Cargo.toml** (root)
+   - Fixed workspace configuration
+
+5. **client/Cargo.toml**
+   - Fixed dependency version conflicts
+
+## Conclusion
+
+The tick function implementation successfully provides trustless automation for the Stellar Save contract, enabling reliable cycle advancement without requiring creator intervention. The implementation is robust, well-tested, and maintains full compatibility with existing contract functionality.