---
# (DD01) Business Logic — ProductService.findByPriceRange() [5 LOC]

| Field | Value |
|-------|-------|
| Fully Qualified Name | `com.example.service.ProductService` |
| Layer | Service |
| Module | `service` (Package: `com.example.service`) |

## 1. Role

### ProductService.findByPriceRange()

`findByPriceRange()` is a service-layer query method that returns the subset of products whose price falls within a caller-defined minimum and maximum boundary. Business-wise, it acts as an in-memory price filter over the product catalog, allowing the application to support price-based browsing, search refinement, or validation use cases without changing the underlying data set. The method uses a stream pipeline to iterate over the current product collection, evaluate each product’s price against both bounds, and retain only those records that satisfy the range criteria. 

This method does not branch by product type or business category; instead, it implements a single filtering rule based on numeric comparison. Its design pattern is a straightforward functional filter-and-collect pipeline, with delegation to the `Product` model for price access and to the Java Stream API for selection and result materialization. In the larger system, the method behaves as a shared read helper inside `ProductService`, suitable for use by UI search screens or other services that need a normalized list of products within a price interval.

## 2. Processing Pattern (Detailed Business Logic)

```mermaid
flowchart TD
    START(["findByPriceRange(min, max)"])
    STREAM(["products.values().stream()"])
    FILTER(["filter(p -> p.getPrice() >= min and <= max)"])
    COLLECT(["collect(Collectors.toList())"])
    END_NODE(["Return List<Product>"])
    START --> STREAM
    STREAM --> FILTER
    FILTER --> COLLECT
    COLLECT --> END_NODE
```

## 3. Parameter Analysis

| No | Parameter Name | Type | Business Description |
|----|---------------|------|---------------------|
| 1 | `min` | `BigDecimal` | Lower bound of the acceptable product price range. Products with prices below this value are excluded from the result. |
| 2 | `max` | `BigDecimal` | Upper bound of the acceptable product price range. Products with prices above this value are excluded from the result. |

External state read by this method:
- `products` — the in-memory catalog map stored in `ProductService`.
- `Product#getPrice()` — price attribute of each product instance used for range comparison.

## 4. CRUD Operations / Called Services

| CRUD | SC / CBS | SC Code | Entity / DB | Operation Description |
|------|----------|---------|-------------|-----------------------|
| R | `findByPriceRange` | N/A | `products` (in-memory collection) | Reads all products from the service cache, filters them by inclusive price range, and returns the matching list. |

The method does not invoke any external SC/CBS service, database mapper, or repository. Its only business operation is a read/filter over the local `products` map.

## 5. Dependency Trace

| # | Caller (Screen/Batch) | Call Chain (Full Path to this Method) | Terminal (SC / CRUD / Entity) |
|---|----------------------|--------------------------------------|-------------------------------|
| 1 | Internal Java caller(s) | `caller -> ProductService.findByPriceRange` | `findByPriceRange [R] products` |

Observed call-site evidence from the code scan shows the method definition itself, but no additional Java caller classes were present in the scanned sources. This method therefore appears to be a reusable internal service query helper rather than an externally routed screen entry point.

## 6. Per-Branch Detail Blocks

**Block 1** — [RETURN] `(single stream pipeline)` (L25)

> Returns all products whose price is within the inclusive range defined by `min` and `max`.

| # | Type | Code |
|---|------|------|
| 1 | EXEC | `products.values().stream();` // create a stream from the current product collection |
| 2 | CALL | `filter(p -> p.getPrice().compareTo(min) >= 0 && p.getPrice().compareTo(max) <= 0);` // keep products priced between the lower and upper bounds |
| 3 | CALL | `collect(Collectors.toList());` // materialize the filtered products as a list |
| 4 | RETURN | `return ...;` // return the matching `List<Product>` |

## 7. Glossary

| Term | Type | Business Meaning |
|------|------|------------------|
| `products` | Field | In-memory product catalog maintained by `ProductService`. |
| `min` | Field | Minimum allowed product price in the search range. |
| `max` | Field | Maximum allowed product price in the search range. |
| `BigDecimal` | Technical type | Decimal numeric type used for monetary comparison without floating-point precision loss. |
| `Product` | Domain object | Business product record containing product identity, stock status, and price. |
| `price` | Field | Monetary value used to determine whether a product belongs in the requested range. |
| Stream API | Technical term | Java functional processing style used to filter and collect products. |
| `collect(Collectors.toList())` | Technical operation | Converts a filtered stream into a concrete list result. |
| `compareTo` | Technical operation | Numeric comparison method used to evaluate whether a product price is above the minimum and below the maximum. |