explain

Explain a code file, function, or architectural pattern in detail with context.

Instructions

1. Read the target that the user specifies:

   • A specific file path
   • A function or class name (search for it in the codebase)
   • A directory (explain the module/package architecture)
   • If nothing specified, use the most recently edited file

2. Determine the appropriate level of explanation:

   • File-level: overall purpose, key exports, dependencies, how it fits in the system
   • Function-level: inputs, outputs, algorithm, edge cases, side effects
   • Architecture-level: component relationships, data flow, design patterns used
   • Line-level: what specific complex lines do (only for genuinely tricky code)

3. Structure the explanation:

For a File

## {filename}

### Purpose
{One paragraph: what this file does and why it exists}

### Key Components
- `{export/class/function}` — {what it does}
- `{export/class/function}` — {what it does}

### Dependencies
- **Imports from:** {list of modules this file depends on}
- **Used by:** {list of files that import from this file}

### Data Flow
{How data enters, is transformed, and exits this file}

### Design Decisions
- {Why was it structured this way?}
- {What patterns are used? (factory, observer, middleware, etc.)}

### Gotchas
- {Non-obvious behavior or edge cases}
- {Things that might surprise a new reader}

For a Function

## `{functionName}()`

### Signature
{full function signature with types}

### Purpose
{What does this function do? One paragraph.}

### Parameters
- `{param}` ({type}): {description, constraints, defaults}

### Returns
- ({type}): {description of return value}

### Algorithm
1. {Step 1}
2. {Step 2}
3. {Step 3}

### Edge Cases
- {What happens with null/empty input?}
- {What happens at boundary values?}
- {What errors can it throw?}

### Example Usage
```{lang}
{realistic usage example}

Side Effects

• {Database writes, HTTP calls, file I/O, global state mutations}

Performance

• Time complexity: O({n})
• Space complexity: O({n})
• {Any known performance considerations}