estimate-builder

# Estimate Builder

## Business Case

### Problem Statement
Estimate creation challenges:
- Complex cost structures
- Multiple cost categories
- Markup calculations
- Format requirements vary

### Solution
Structured estimate builder that creates professional construction estimates with proper cost categorization, markups, and export capabilities.

## Technical Implementation

```python
import pandas as pd
from typing import Dict, Any, List, Optional
from dataclasses import dataclass, field
from datetime import date
from enum import Enum


class CostCategory(Enum):
    LABOR = "labor"
    MATERIAL = "material"
    EQUIPMENT = "equipment"
    SUBCONTRACTOR = "subcontractor"
    OTHER = "other"


@dataclass
class EstimateLineItem:
    line_number: int
    wbs_code: str
    description: str
    quantity: float
    unit: str
    unit_cost: float
    category: CostCategory
    notes: str = ""

    @property
    def total_cost(self) -> float:
        return round(self.quantity * self.unit_cost, 2)


@dataclass
class CostSummary:
    labor: float = 0
    material: float = 0
    equipment: float = 0
    subcontractor: float = 0
    other: float = 0

    @property
    def direct_cost(self) -> float:
        return self.labor + self.material + self.equipment + self.subcontractor + self.other


@dataclass
class Markup:
    name: str
    rate: float  # As decimal (0.10 = 10%)
    base: str = "direct"  # "direct" or "subtotal"


class EstimateBuilder:
    """Build construction project estimates."""

    def __init__(self, project_name: str, project_number: str = ""):
        self.project_name = project_name
        self.project_number = project_number
        self.estimate_date = date.today()
        self.items: List[EstimateLineItem] = []
        self.markups: List[Markup] = []
        self._next_line = 1

    def add_item(self,
                 wbs_code: str,
                 description: str,...