# JSPG: JSON Schema Postgres

**JSPG** is a high-performance PostgreSQL extension written in Rust (using `pgrx`) that transforms Postgres into a pre-compiled Semantic Engine. It serves as the core engine for the "Punc" architecture, where the database is the single source of truth for all data models, API contracts, validations, and reactive queries.

## 1. Overview & Architecture

JSPG operates by deeply integrating the JSON Schema Draft 2020-12 specification directly into the Postgres session lifecycle. It is built around three core pillars:
*   **Validator**: In-memory, near-instant JSON structural validation and type polymorphism routing.
*   **Merger**: Automatically traverse and UPSERT deeply nested JSON graphs into normalized relational tables.
*   **Queryer**: Compile JSON Schemas into static, cached SQL SPI `SELECT` plans for fetching full entities or isolated "Stems".

### 🎯 Goals
1.  **Draft 2020-12 Compliance**: Attempt to adhere to the official JSON Schema Draft 2020-12 specification.
2.  **Ultra-Fast Execution**: Compile schemas into optimized in-memory validation trees and cached SQL SPIs to bypass Postgres Query Builder overheads.
3.  **Connection-Bound Caching**: Leverage the PostgreSQL session lifecycle using an **Atomic Swap** pattern. Schemas are 100% frozen, completely eliminating locks during read access.
4.  **Structural Inheritance**: Support object-oriented schema design via Implicit Keyword Shadowing and virtual `$family` references natively mapped to Postgres table constraints.
5.  **Reactive Beats**: Provide natively generated "Stems" (isolated payload fragments) for dynamic websocket reactivity.

### Concurrency & Threading ("Immutable Graphs")
To support high-throughput operations while allowing for runtime updates (e.g., during hot-reloading), JSPG uses an **Atomic Swap** pattern:
1. **Parser Phase**: Schema JSONs are parsed into ordered `Schema` structs.
2. **Compiler Phase**: The database iterates all parsed schemas and pre-computes native optimization maps (Descendants Map, Depths Map, Variations Map).
3. **Immutable Validator**: The `Validator` struct immutably owns the `Database` registry and all its global maps. Schemas themselves are completely frozen; `$ref` strings are resolved dynamically at runtime using pre-computed O(1) maps.
4. **Lock-Free Reads**: Incoming operations acquire a read lock just long enough to clone the `Arc` inside an `RwLock<Option<Arc<Validator>>>`, ensuring zero blocking during schema updates.

---

## 2. Validator

The Validator provides strict, schema-driven evaluation for the "Punc" architecture.

### API Reference
*   `jspg_setup(database jsonb) -> jsonb`: Loads and compiles the entire registry (types, enums, puncs, relations) atomically.
*   `mask_json_schema(schema_id text, instance jsonb) -> jsonb`: Validates and prunes unknown properties dynamically, returning masked data.
*   `jspg_validate(schema_id text, instance jsonb) -> jsonb`: Returns boolean-like success or structured errors.
*   `jspg_teardown() -> jsonb`: Clears the current session's schema cache.

### Custom Features & Deviations
JSPG implements specific extensions to the Draft 2020-12 standard to support the Punc architecture's object-oriented needs while heavily optimizing for zero-runtime lookups.

#### A. Polymorphism & Referencing (`$ref`, `$family`, and Native Types)
*   **Native Type Discrimination (`variations`)**: Schemas defined inside a Postgres `type` are Entities. The validator securely and implicitly manages their `"type"` property. If an entity inherits from `user`, incoming JSON can safely define `{"type": "person"}` without errors, thanks to `compiled_variations` inheritance.
*   **Structural Inheritance & Viral Infection (`$ref`)**: `$ref` is used exclusively for structural inheritance, *never* for union creation. A Punc request schema that `$ref`s an Entity virally inherits all physical database polymorphism rules for that target.
*   **Shape Polymorphism (`$family`)**: Auto-expands polymorphic API lists based on an abstract Descendants Graph. If `{"$family": "widget"}` is used, JSPG evaluates the JSON against every schema that `$ref`s widget.
*   **Strict Matches & Depth Heuristic**: Polymorphic structures MUST match exactly **one** schema permutation. If multiple inherited struct permutations pass, JSPG applies the **Depth Heuristic Tie-Breaker**, selecting the candidate deepest in the inheritance tree. 

#### B. Dot-Notation Schema Resolution & Database Mapping
*   **The Dot Convention**: When a schema represents a specific variation or shape of an underlying physical database `Type` (e.g., a "summary" of a "person"), its `$id` must adhere to a dot-notation suffix convention (e.g., `summary.person` or `full.person`). 
*   **Entity Resolution**: The framework (Validator, Queryer, Merger) dynamically determines the backing PostgreSQL table structure by splitting the schema's `$id` (or `$ref`) by `.` and extracting the **last segment** (`next_back()`). If the last segment matches a known Database Type (like `person`), the framework natively applies that table's inheritance rules, variations, and physical foreign keys to the schema graph, regardless of the prefix.

#### C. Strict by Default & Extensibility
*   **Strictness**: By default, any property not explicitly defined in the schema causes a validation error (effectively enforcing `additionalProperties: false` globally). 
*   **Extensibility (`extensible: true`)**: To allow a free-for-all of undefined properties, schemas must explicitly declare `"extensible": true`. 
*   **Structured Additional Properties**: If `additionalProperties: {...}` is defined as a schema, arbitrary keys are allowed so long as their values match the defined type constraint.
*   **Inheritance Boundaries**: Strictness resets when crossing `$ref` boundaries. A schema extending a strict parent remains strict unless it explicitly overrides with `"extensible": true`.

#### D. Implicit Keyword Shadowing
*   **Inheritance (`$ref` + properties)**: Unlike standard JSON Schema, when a schema uses `$ref` alongside local properties, JSPG implements **Smart Merge**. Local constraints natively take precedence over (shadow) inherited constraints for the same keyword. 
    *   *Example*: If `entity` has `type: {const: "entity"}`, but `person` defines `type: {const: "person"}`, the local `person` const cleanly overrides the inherited one.
*   **Composition (`allOf`)**: When evaluating `allOf`, standard intersection rules apply seamlessly. No shadowing occurs, meaning all constraints from all branches must pass.

#### E. Format Leniency for Empty Strings
To simplify frontend form validation, format validators specifically for `uuid`, `date-time`, and `email` explicitly allow empty strings (`""`), treating them as "present but unset".

---


## 3. Merger

The Merger provides an automated, high-performance graph synchronization engine via the `jspg_merge(cue JSONB)` API. It orchestrates the complex mapping of nested JSON objects into normalized Postgres relational tables, honoring all inheritance and graph constraints.

### Core Features

*   **Deep Graph Merging**: The Merger walks arbitrary levels of deeply nested JSON schemas (e.g. tracking an `order`, its `customer`, and an array of its `lines`). It intelligently discovers the correct parent-to-child or child-to-parent Foreign Keys stored in the registry and automatically maps the UUIDs across the relationships during UPSERT.
*   **Prefix Foreign Key Matching**: Handles scenario where multiple relations point to the same table by using database Foreign Key constraint prefixes (`fk_`). For example, if a schema has `shipping_address` and `billing_address`, the merger resolves against `fk_shipping_address_entity` vs `fk_billing_address_entity` automatically to correctly route object properties.
*   **Dynamic Deduplication & Lookups**: If a nested object is provided without an `id`, the Merger utilizes Postgres `lk_` index constraints defined in the schema registry (e.g. `lk_person` mapped to `first_name` and `last_name`). It dynamically queries these unique matching constraints to discover the correct UUID to perform an UPDATE, preventing data duplication.
*   **Hierarchical Table Inheritance**: The Punc system uses distributed table inheritance (e.g. `person` inherits `user` inherits `organization` inherits `entity`). The Merger splits the incoming JSON payload and performs atomic row updates across *all* relevant tables in the lineage map.
*   **The Archive Paradigm**: Data is never deleted in the Punc system. The Merger securely enforces referential integrity by toggling the `archived` Boolean flag on the base `entity` table rather than issuing SQL `DELETE` commands.
*   **Change Tracking & Reactivity**: The Merger diffs the incoming JSON against the existing database row (utilizing static, `DashMap`-cached `lk_` SELECT string templates). Every detected change is recorded into the `agreego.change` audit table, tracking the user mapping. It then natively uses `pg_notify` to broadcast a completely flat row-level diff out to the Go WebSocket server for O(1) routing.
*   **Many-to-Many Graph Edge Management**: Operates seamlessly with the global `agreego.relationship` table, allowing the system to represent and merge arbitrary reified M:M relationships directionally between any two entities.
*   **Sparse Updates**: Empty JSON strings `""` are directly bound as explicit SQL `NULL` directives to clear data, whilst omitted (missing) properties skip UPDATE execution entirely, ensuring partial UI submissions do not wipe out sibling fields.
*   **Unified Return Structure**: To eliminate UI hydration race conditions and multi-user duplication, `jspg_merge` explicitly strips the response graph and returns only the root `{ "id": "uuid" }` (or an array of IDs for list insertions). External APIs can then explicitly call read APIs to fetch the resulting graph, while the UI relies 100% implicitly on the flat `pg_notify` pipeline for reactive state synchronization.
*   **Decoupled SQL Generation**: Because Writes (INSERT/UPDATE) are inherently highly dynamic based on partial payload structures, the Merger generates raw SQL strings dynamically per execution without caching, guaranteeing a minimal memory footprint while scaling optimally.

---

## 4. Queryer

The Queryer transforms Postgres into a pre-compiled Semantic Query Engine via the `jspg_query(schema_id text, cue jsonb)` API, designed to serve the exact shape of Punc responses directly via SQL.

### Core Features
*   **Schema-to-SQL Compilation**: Compiles JSON Schema ASTs spanning deep arrays directly into static, pre-planned SQL multi-JOIN queries. This explicitly features the `Smart Merge` evaluation engine which natively translates properties through `allOf` and `$ref` inheritances, mapping JSON fields specifically to their physical database table aliases during translation.
*   **DashMap SQL Caching**: Executes compiled SQL via Postgres SPI execution, securely caching the static string compilation templates per schema permutation inside the `GLOBAL_JSPG` application memory, drastically reducing repetitive schema crawling.
*   **Dynamic Filtering**: Binds parameters natively through `cue.filters` objects. Dynamically handles string formatting (e.g. parsing `uuid` or formatting date-times) and safely escapes complex combinations utilizing `ILIKE` operations correctly mapped to the originating structural table.
### 4. The Stem Engine

Rather than over-fetching heavy Entity payloads and trimming them, Punc Framework Websockets depend on isolated subgraphs defined as **Stems**.
A `Stem` is **not a JSON Pointer** or a physical path string (like `/properties/contacts/items/phone_number`). It is simply a declaration of an **Entity Type boundary** that exists somewhere within the compiled JSON Schema graph. 

Because `pg_notify` (Beats) fire rigidly from physical Postgres tables (e.g. `{"type": "phone_number"}`), the Go Framework only ever needs to know: "Does the schema `with_contacts.person` contain the `phone_number` Entity anywhere inside its tree?"

*   **Initialization:** During startup (`jspg_stems()`), the database crawls all Schemas and maps out every physical Entity Type it references. It builds a flat dictionary of `Schema ID -> [Entity Types]` (e.g. `with_contacts.person -> ["person", "contact", "phone_number", "email_address"]`).
*   **Relationship Path Squashing:** When calculating nested string paths structurally to discover these boundaries, JSPG intentionally **omits** properties natively named `target` or `source` if they belong to a native database `relationship` table override. This ensures paths like `phone_numbers/contact/target` correctly register their beat resolution pattern as `phone_numbers/contact/phone_number`.
*   **The Go Router**: The Golang Punc framework uses this exact mapping to register WebSocket Beat frequencies exclusively on the Entity types discovered.
*   **The Queryer Execution**: When the Go framework asks JSPG to hydrate a partial `phone_number` stem for the `with_contacts.person` schema, instead of jumping through string paths, the SQL Compiler simply reaches into the Schema's AST using the `phone_number` Type string, pulls out exactly that entity's mapping rules, and returns a fully correlated `SELECT` block! This natively handles nested array properties injected via `oneOf` or array references efficiently bypassing runtime powerset expansion.
*   **Performance:** These Stem execution structures are fully statically compiled via SPI and map perfectly to `O(1)` real-time routing logic on the application tier.


## 5. Testing & Execution Architecture

JSPG implements a strict separation of concerns to bypass the need to boot a full PostgreSQL cluster for unit and integration testing. Because `pgrx::spi::Spi` directly links to PostgreSQL C-headers, building the library with `cargo test` on macOS natively normally results in fatal `dyld` crashes.

To solve this, JSPG introduces the `DatabaseExecutor` trait inside `src/database/executors/`:

*   **`SpiExecutor` (`pgrx.rs`)**: The production evaluator that is conditionally compiled (`#[cfg(not(test))]`). It unwraps standard `pgrx::spi` connections to the database.
*   **`MockExecutor` (`mock.rs`)**: The testing evaluator that is conditionally compiled (`#[cfg(test)]`). It absorbs SQL calls and captures parameter bindings in memory without executing them.

### Universal Test Harness (`src/tests/`)
JSPG abandons the standard `cargo pgrx test` model in favor of native OS testing for a >1000x speed increase (`~0.05s` execution).

1.  **JSON Fixtures**: All core interactions are defined abstractly as JSON arrays in `fixtures/`. Each file contains suites of `TestCase` objects with an `action` flag (`validate`, `merge`, `query`).
2.  **`build.rs` Generator**: The build script traverses the JSON fixtures, extracts their structural identities, and generates standard `#[test]` blocks into `src/tests/fixtures.rs`.
3.  **Modular Test Dispatcher**: The `src/tests/types/` module deserializes the abstract JSON test payloads into `Suite`, `Case`, and `Expect` data structures.
4.  **Unit Context Execution**: When `cargo test` executes, the `Runner` feeds the JSON payloads directly into `case.execute(db)`. Because the tests run natively inside the module via `#cfg(test)`, the Rust compiler globally erases `pgrx` C-linkage, instantiates the `MockExecutor`, and allows for pure structural evaluation of complex database logic completely in memory.
