Add canonical route cache key derivation and tests

[leynos]

Summary

• Introduces domain-owned canonicalization for route cache keys. Added a constructor that derives RouteCacheKey from a route request payload, ensuring semantically equivalent requests map to the same cache key (namespace route:v1 with a sha256 digest).
• Reuses existing domain hashing while applying normalization rules: sorted object keys, stable theme arrays, and rounded coordinates.
• Adds unit and behavioural tests, plus focused documentation to reflect the new canonicalization seam.

Changes

Core functionality

• Implemented RouteCacheKey::for_route_request(payload) in backend/src/domain/ports/cache_key.rs
  • Normalizes payload before hashing to produce a stable digest.
  • Normalization rules include:
    • Sort object keys at every level
    • Sort documented array fields (themes, themeIds, interestThemeIds) when they are arrays of strings
    • Round coordinate fields (lat, lng, lon, latitude, longitude) to five decimal places
  • Final key format remains route:v1: using the existing payload hashing helper.
• Added support types and helpers within the same module:
  • const ROUTE_CACHE_NAMESPACE, COORDINATE_PRECISION_FACTOR, SORTED_ARRAY_KEYS, ROUNDED_COORDINATE_KEYS
  • normalize_route_request_value, should_sort_array, should_round_coordinate, round_coordinate
• Public API exposure
  • RouteCacheKeyDerivationError is introduced and exported (alongside RouteCacheKeyValidationError) to describe derivation failures.
  • RouteCacheKey::for_route_request returns Result<Self, RouteCacheKeyDerivationError> and validates the final key.

Public API surface

• Updated backend/src/domain/ports/mod.rs to export RouteCacheKeyDerivationError (in addition to RouteCacheKeyValidationError)
• RouteCacheKey now provides a stable, derivation-based constructor for route requests.

Tests

• Added unit tests for canonicalization in backend/src/domain/ports/cache_key.rs (within the existing #[cfg(test)] mod tests)
  • Verifies namespace and hash shape (route:v1: with 64 lowercase hex chars)
  • Verifies sorting of documented theme arrays for multiple fields
  • Verifies rounding behavior on coordinate fields
  • Verifies that material payload differences change the key
  • Verifies non-theme array orders are not altered (and still affect the key)
• Introduced Redis-backed behavioural tests to validate integration between canonical keys and caching:
  • backend/tests/features/route_cache_key_canonicalization.feature
  • backend/tests/route_cache_key_canonicalization_bdd.rs
  • These tests require a running Redis server; they are designed to be skipped if Redis is unavailable or SKIP_REDIS_TESTS is set.

Documentation

• New ExecPlan doc: docs/execplans/backend-5-1-4-cache-key-canonicalization-contract-tests.md
• Architecture docs updated to reflect the canonicalization seam ownership:
  • docs/wildside-backend-architecture.md now notes that RouteCacheKey encapsulates canonical derivation and that the Redis adapter persists the derived key.

Validation notes

• The unit tests target the canonicalization contract and payload normalization logic.
• Redis-backed behavioural tests are gated and will be skipped when Redis is unavailable or SKIP_REDIS_TESTS is set. When run with Redis available, they validate the end-to-end behavior:
  • Equivalent route requests canonicalize to the same key
  • A plan stored under the first canonical key can be retrieved using the second canonical key
  • The canonical key follows the route v1 sha256 format

How to test locally

• Fast unit tests (without Redis):
  • cargo test -p backend route_request_key --lib (or run the project’s full unit test suite)
• Redis-backed behaviour tests (requires Redis in PATH):
  • SKIP_REDIS_TESTS=0 cargo test -p backend --test route_cache_key_canonicalization_bdd -- --nocapture
• If Redis is not available, set SKIP_REDIS_TESTS=1 to skip the behavioural tests while still running unit tests.

Rationale / design notes

• The canonicalization seam remains in the domain layer to satisfy the contract that the service owns normalization and namespace rules, not the Redis adapter.
• The implementation reuses the existing domain hash helper to avoid duplicating SHA-256 logic and to ensure consistency across the codebase.
• A new RouteCacheKeyDerivationError surface provides a precise error taxonomy for key derivation failures while preserving compatibility with existing error types.

Risks and mitigations

• Overfitting normalization rules could affect cache usefulness. Mitigation: adhere strictly to documented semantics (sorted arrays, rounded coordinates, stable object order).
• Redis-backed tests introduce environmental dependency. Mitigation: keep tests gated and provide clear skip messaging when Redis is unavailable.

Progress indicators

• Implemented domain-owned canonical route cache key derivation
• Added focused unit tests and Redis-backed behavioural tests
• Updated architectural and execplan documentation to reflect the new contract
• Exported new derivation error type for downstream consumers

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📎 Task: https://www.devboxer.com/task/013b1644-7ade-47fd-a954-ba6ec8fda3ff

Summary by Sourcery

Introduce domain-owned canonical route cache key derivation for route requests and validate it with unit, integration, and documentation updates.

New Features:

• Add RouteCacheKey::for_route_request constructor to derive canonical cache keys from route request JSON payloads using a stable namespace and hash format.
• Expose RouteCacheKeyDerivationError as a public error type for cache key derivation failures.

Enhancements:

• Normalize route request payloads before hashing by sorting object keys, sorting specific theme arrays, and rounding coordinate fields to five decimal places.
• Clarify architecture documentation to state that RouteCacheKey owns canonical cache key derivation while the Redis adapter only persists derived keys.

Documentation:

• Add an ExecPlan document describing the route cache key canonicalization contract tests, constraints, risks, and validation steps.
• Update backend architecture documentation to document the canonicalization seam location and responsibilities.

Tests:

• Add unit tests covering canonical cache key format, array sorting behavior, coordinate rounding, and sensitivity to material payload differences.
• Add Redis-backed BDD tests and feature scenarios to verify that semantically equivalent route requests share a single Redis cache entry and respect the route:v1 sha256 key format.

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[sourcery-ai]

Reviewer's Guide

Implements domain-owned canonical route cache key derivation for route requests, exposes a new derivation error type, adds unit and Redis-backed behavioural tests around canonicalization, and updates architecture/execplan docs to reflect the new cache-key seam.

Class diagram for RouteCacheKey canonical derivation and errors

classDiagram
    class RouteCacheKey {
        -String value
        +RouteCacheKey new(String raw) Result~RouteCacheKey, RouteCacheKeyValidationError~
        +RouteCacheKey for_route_request(Value payload) Result~RouteCacheKey, RouteCacheKeyDerivationError~
        +&str as_str()
        +String to_string()
    }

    class RouteCacheKeyValidationError {
        <<enum>>
        +InvalidNamespace
        +InvalidHashLength
        +InvalidCharacters
        +ContainsWhitespace
    }

    class RouteCacheKeyDerivationError {
        <<enum>>
        +Hash
        +Validation
    }

    class PayloadHashError {
        <<error>>
    }

    class RouteRequestNormalizer {
        <<utility>>
        +Value normalize_route_request_value(Value value, Option~&str~ current_key)
        +bool should_sort_array(Option~&str~ current_key)
        +bool should_round_coordinate(Option~&str~ current_key)
        +Number round_coordinate(Number number)
        +const ROUTE_CACHE_NAMESPACE : &str
        +const COORDINATE_PRECISION_FACTOR : f64
        +const SORTED_ARRAY_KEYS : &[&str]
        +const ROUNDED_COORDINATE_KEYS : &[&str]
    }

    class DomainHashing {
        <<utility>>
        +String canonicalize_and_hash(Value value) Result~String, PayloadHashError~
    }

    RouteCacheKey --> RouteCacheKeyValidationError : uses
    RouteCacheKey --> RouteCacheKeyDerivationError : returns
    RouteCacheKeyDerivationError --> RouteCacheKeyValidationError : wraps
    RouteCacheKeyDerivationError --> PayloadHashError : wraps
    RouteCacheKey --> RouteRequestNormalizer : uses
    RouteCacheKey --> DomainHashing : uses

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File-Level Changes

Change	Details	Files
Add canonical RouteCacheKey derivation from route request payloads with normalization rules before hashing.	Introduce RouteCacheKey::for_route_request(&Value) that normalizes the payload, hashes it via canonicalize_and_hash, and prefixes it with the route:v1 namespace. Define constants for route cache namespace, coordinate precision, sortable array keys, and rounded coordinate keys. Implement normalize_route_request_value to recursively sort object keys, sort selected string arrays, and round selected numeric coordinate fields before hashing. Add helpers should_sort_array, should_round_coordinate, and round_coordinate, reusing serde_json::Value/Number types.	backend/src/domain/ports/cache_key.rs
Extend cache key error surface with a derivation error type and export it from the domain ports module.	Add RouteCacheKeyDerivationError enum to wrap PayloadHashError and RouteCacheKeyValidationError from derivation. Change RouteCacheKey::for_route_request to return Result<Self, RouteCacheKeyDerivationError> and map validation failures accordingly. Re-export RouteCacheKeyDerivationError in domain ports mod so adapters can depend on it.	backend/src/domain/ports/cache_key.rs backend/src/domain/ports/mod.rs
Add unit tests validating canonicalization behaviour and key format for route cache keys.	Extend existing cache_key tests module to cover namespace and sha256 digest shape for route:v1 keys. Add rstest-based cases ensuring documented theme arrays are sorted but non-theme arrays remain order-sensitive. Add tests verifying rounding behaviour for documented coordinate fields and that material payload differences change the key.	backend/src/domain/ports/cache_key.rs
Introduce Redis-backed BDD tests and feature describing canonical route cache key behaviour end-to-end.	Create RouteCacheKeyWorld test harness that bootstraps a temporary Redis server, handles skip logic via SKIP_REDIS_TESTS and should_skip_redis_tests, and wires a RedisRouteCache. Derive two RouteCacheKey values from semantically equivalent JSON payloads and assert equality plus route:v1 sha256 format. Store a TestPlan under the first key, read with the second key, and assert the same plan is returned. Back the scenario with a Gherkin feature file documenting the canonicalization behaviour and Redis dependency.	backend/tests/route_cache_key_canonicalization_bdd.rs backend/tests/features/route_cache_key_canonicalization.feature
Update and add documentation to describe the canonicalization contract and its implementation status.	Update architecture doc to describe RouteCacheKey as owning canonical cache-key derivation and to document that canonicalization lives in backend/src/domain/ports/cache_key.rs while the Redis adapter just persists the derived key. Add an ExecPlan document capturing constraints, risks, implementation outline, progress, and validation strategy for the cache key canonicalization contract tests.	docs/wildside-backend-architecture.md docs/execplans/backend-5-1-4-cache-key-canonicalization-contract-tests.md

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