# 📖 Code Explanation: Grammar & Spelling Corrector

This document provides a step-by-step explanation of the **Grammar & Spelling Corrector** app, showing how each part works so even a beginner can follow.

---

## 📝 Overview

**Purpose**  
Improve grammar and spelling of English sentences or paragraphs using a state-of-the-art NLP model.

**Tech Stack**  
- **Model**: `grammarly/coedit-large` (Hugging Face Transformers)  
- **Interface**: Gradio Blocks + Buttons

---

## ⚙️ Setup & Dependencies

Install required libraries:

```
pip install transformers gradio torch
```

---

## 🔍 Block-by-Block Explanation

### 1. Imports

```python
from transformers import pipeline
import gradio as gr
import torch
```

- **`pipeline`**: high-level API to load pre-trained models for various tasks.  
- **`gradio`**: library to quickly build web interfaces.

### 2. Model Loading

```python
pipe = pipeline(
    "text2text-generation",
    model="grammarly/coedit-large,
    torch_dtype=torch.bfloat16
)
```

- Loads the **CoEdit** model, fine-tuned for grammar and spelling correction.  
- The pipeline can generate corrected text from raw input.

### 3. Grammar Correction Function

```python
def correct_grammar(text: str) -> str:
    outputs = pipe(
        text,
        max_length=256,
        num_beams=5,
        early_stopping=True
    )
    return outputs[0]["generated_text"]
```

- **Input**: raw English text.  
- **Parameters**:  
  - `max_length=256`: maximum tokens for output.  
  - `num_beams=5`: beam search for more accurate generation.  
  - `early_stopping=True`: stop beams when best hypothesis is found.  
- **Output**: corrected text string.

### 4. Gradio User Interface

```python
with gr.Blocks(theme=gr.themes.Default()) as demo:
    gr.Markdown("# 📝 Grammar & Spelling Corrector")
    gr.Markdown("Paste any English sentence or paragraph below to get a corrected version.")

    with gr.Row():
        inp = gr.Textbox(
            label="✍️ Input Text",
            placeholder="Type your text here...",
            lines=4,
            show_copy_button=True
        )
        out = gr.Textbox(
            label="✅ Corrected Text",
            placeholder="Corrected text appears here.",
            lines=4,
            interactive=False,
            show_copy_button=True
        )

    btn = gr.Button("✔️ Correct Grammar")
    btn.click(fn=correct_grammar, inputs=inp, outputs=out)

    gr.Markdown("---")
    gr.Markdown("Built with 🤗 Transformers (`grammarly/coedit-large`) and 🚀 Gradio")

demo.launch()
```

- **Blocks** and **Rows** organize layout.  
- **Textbox** for input and output.  
- **Button** triggers the `correct_grammar` function.

---

## 🚀 Core Concepts

| Concept               | Why It Matters                                  |
|-----------------------|-------------------------------------------------|
| Hugging Face Pipeline | Simplifies loading and using pre-trained models |
| CoEdit Model          | Specialized for grammar and spelling correction |
| Gradio Interface      | Quickly builds interactive web apps            |

---

## 🔄 Extensions & Alternatives

- **Alternative Models**:  
  - `prithivida/grammar_error_correcter_v1` (T5-based)  
  - `microsoft/trocr-base-handwritten` for OCR + correction  

- **UI Enhancements**:  
  - Add file upload for batch corrections.  
  - Include copy-to-clipboard buttons and download corrected text.  

- **Performance**:  
  - Enable GPU support for faster inference.  
  - Experiment with `torch_dtype=torch.bfloat16` on supported hardware.