import gradio as gr
from fastapi import FastAPI, HTTPException
from pydantic import BaseModel, field_validator
from frontend import create_interface
import math
import re
import os

app = FastAPI()

ALLOWED_FUNCTIONS = {'sin', 'cos', 'tan', 'log', 'ln', 'sqrt', 'abs', 'pow'}
ALLOWED_CONSTANTS = {'pi', 'e'}

class Expression(BaseModel):
    expr: str

    @field_validator('expr')
    @classmethod
    def validate_expression(cls, v: str) -> str:
        if not v:
            raise ValueError("Expression cannot be empty")
        
        # Check for invalid characters
        valid_chars = set('0123456789.+-*/()^ \t\nabcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
        invalid_chars = set(v) - valid_chars
        if invalid_chars:
            raise ValueError(f"Invalid characters found: {', '.join(invalid_chars)}")
        
        # Check for invalid function names or constants
        tokens = re.findall(r'\b[a-zA-Z_]\w*\b', v)
        invalid_tokens = [token for token in tokens if token not in ALLOWED_FUNCTIONS and token not in ALLOWED_CONSTANTS]
        if invalid_tokens:
            raise ValueError(f"Invalid function or constant names: {', '.join(invalid_tokens)}")
        
        return v

@app.post("/calculate")
async def calculate_api(expression: Expression):
    try:
        result = evaluate_expression(expression.expr)
        return {"result": result}
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"An unexpected error occurred: {str(e)}")

def evaluate_expression(expr: str) -> float:
    safe_dict = {
        'sin': math.sin, 'cos': math.cos, 'tan': math.tan,
        'log': math.log10, 'ln': math.log, 'sqrt': math.sqrt,
        'pi': math.pi, 'e': math.e,
        'abs': abs, 'pow': pow
    }
    try:
        # Replace '^' with '**' for exponentiation
        expr = expr.replace('^', '**')
        return eval(expr, {"__builtins__": None}, safe_dict)
    except ZeroDivisionError:
        raise ValueError("Division by zero is not allowed")
    except ValueError as e:
        raise ValueError(f"Math domain error: {str(e)}")
    except Exception as e:
        raise ValueError(f"Invalid expression: {str(e)}")

# Create the Gradio interface
iface = create_interface()

# Mount the Gradio app
app = gr.mount_gradio_app(app, iface, path="/")

if __name__ == "__main__":
    import uvicorn
    port = int(os.environ.get("PORT", 7860))
    uvicorn.run(app, host="0.0.0.0", port=port)