#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Examples of sorting in Python.

This file demonstrates various sorting methods:
- Basic sorting with sorted() and .sort()
- Key-based sorting (key=)
- Custom sorting functions
- Sorting complex structures (list of dictionaries)
- Stable sorting
"""

from typing import List, Dict, Tuple, Any
from operator import itemgetter, attrgetter


# --- Basic Examples ---

# 1. Sorting a list with sorted() (returns a new list)
numbers: List[int] = [3, 1, 4, 1, 5, 9, 2, 6, 5]
sorted_numbers: List[int] = sorted(numbers)
print("Sorting with sorted():", sorted_numbers)
print("Original list unchanged:", numbers)

# 2. Sorting a list with .sort() (modifies the original list)
numbers.sort()
print("Sorting with .sort():", numbers)


# --- Key-based Sorting ---

# 3. Sorting strings by length
words: List[str] = ["apple", "banana", "cherry", "date", "fig"]
sorted_by_length: List[str] = sorted(words, key=len)
print("\nSorting strings by length:", sorted_by_length)

# 4. Sorting a dictionary by keys
data: Dict[str, int] = {
    "banana": 3,
    "apple": 2,
    "pear": 1,
    "orange": 4
}
sorted_items: List[Tuple[str, int]] = sorted(data.items(), key=lambda x: x[0])
print("\nSorting dictionary by keys:", sorted_items)

# 5. Sorting a dictionary by values
sorted_by_value: List[Tuple[str, int]] = sorted(data.items(), key=lambda x: x[1])
print("Sorting dictionary by values:", sorted_by_value)


# --- Custom Sorting Functions ---

# 6. Sorting by last letter
def sort_by_last_letter(word: str) -> str:
    """Return the last letter of a word for sorting."""
    return word[-1]


sorted_by_last_letter: List[str] = sorted(words, key=sort_by_last_letter)
print("\nSorting by last letter:", sorted_by_last_letter)


# --- Sorting Complex Structures ---

# 7. Sorting a list of dictionaries
people: List[Dict[str, Any]] = [
    {"name": "Alice", "age": 30},
    {"name": "Bob", "age": 25},
    {"name": "Charlie", "age": 35},
    {"name": "David", "age": 25}
]

# Sorting by age
sorted_by_age: List[Dict[str, Any]] = sorted(people, key=lambda x: x["age"])
print("\nSorting people by age:", sorted_by_age)

# Sorting by name
sorted_by_name: List[Dict[str, Any]] = sorted(people, key=lambda x: x["name"])
print("Sorting people by name:", sorted_by_name)

# 8. Sorting by multiple criteria (age, then name)
sorted_by_age_then_name: List[Dict[str, Any]] = sorted(
    people, key=itemgetter("age", "name")
)
print("\nSorting by age, then by name:", sorted_by_age_then_name)


# --- Stable Sorting ---

# 9. Stable sorting (preserves order of equal elements)
# Python uses Timsort, which is stable

# Add unique identifier to demonstrate stability
people_with_id: List[Dict[str, Any]] = [
    {"name": "Alice", "age": 30, "id": 1},
    {"name": "Bob", "age": 25, "id": 2},
    {"name": "Charlie", "age": 35, "id": 3},
    {"name": "David", "age": 25, "id": 4}
]

# First sort by name
sorted_by_name_stable: List[Dict[str, Any]] = sorted(
    people_with_id, key=lambda x: x["name"]
)
print(
    "\nSorting by name (original order for equal ages):",
    sorted_by_name_stable
)

# Now sort by age - order for Bob and David will be preserved
sorted_by_age_stable: List[Dict[str, Any]] = sorted(
    people_with_id, key=lambda x: x["age"]
)
print(
    "Sorting by age (stable, Bob/David order preserved):",
    sorted_by_age_stable
)


# --- Additional Examples ---

# 10. Reverse sorting
reverse_sorted: List[int] = sorted(numbers, reverse=True)
print("\nReverse sorting:", reverse_sorted)


# 11. Sorting using __lt__ (for custom classes)
class Person:
    """A simple class representing a person with name and age."""

    def __init__(self, name: str, age: int) -> None:
        self.name = name
        self.age = age

    def __repr__(self) -> str:
        return f"Person({self.name}, {self.age})"

    def __lt__(self, other: "Person") -> bool:
        return self.age < other.age


people_objects: List[Person] = [
    Person("Alice", 30),
    Person("Bob", 25),
    Person("Charlie", 35)
]
sorted_people: List[Person] = sorted(people_objects)
print("\nSorting Person objects:", sorted_people)

# 12. Sorting using attrgetter
sorted_by_name_attr: List[Person] = sorted(people_objects, key=attrgetter("name"))
print("Sorting objects by 'name' attribute:", sorted_by_name_attr)