# Example 16: HashMap@(K, V)
#
# This example demonstrates Sushi's HashMap@(K, V) generic hash table, which
# provides O(1) average-case lookups using open addressing with linear
# probing and automatic resizing at 0.75 load factor.
#
# Key concepts covered:
# - Generic hash table HashMap@(K, V) with compile-time type specialization
# - HashMap creation with .new()
# - Inserting key-value pairs with .insert()
# - Safe lookups with .get() returning Maybe@(V)
# - Checking key existence with .contains_key()
# - Removing entries with .remove() returning Maybe@(V)
# - Automatic resizing when load factor exceeds 0.75
# - Auto-derived .hash() for all types enables HashMap usage
#
# Note: HashMap uses power-of-two capacities for fast indexing via bitwise AND.
# Keys must implement .hash() -> u64 (auto-derived for primitives, strings, structs, enums).

use <collections/hashmap>

fn main() i32:
    # Create empty hash map with default capacity
    let HashMap@(string, i32) ages = HashMap.new()

    # Insert key-value pairs - automatically resizes when needed
    ages.insert("Arthur", 42)
    ages.insert("Ford", 200)
    ages.insert("Zaphod", 150)
    ages.insert("Trillian", 35)
    ages.insert("Marvin", 1000000)

    println("Number of crew members: {ages.len()}")

    # Safe lookup with .get() - returns Maybe@(V)
    match ages.get("Arthur"):
        Maybe.Some(age) ->
            println("Arthur's age: {age}")
        Maybe.None() ->
            println("Arthur not found")

    # Check if key exists without retrieving the value
    if (ages.contains_key("Marvin")):
        println("Marvin is in the crew")

    # Update value by inserting with the same key
    # .insert() replaces the old value if the key exists
    ages.insert("Arthur", 43)

    match ages.get("Arthur"):
        Maybe.Some(age) ->
            println("Arthur's updated age: {age}")
        Maybe.None() ->
            println("Not found")

    # Remove entry - returns Maybe@(V) with the old value
    match ages.remove("Zaphod"):
        Maybe.Some(age) ->
            println("Removed Zaphod (age {age})")
        Maybe.None() ->
            println("Zaphod not found")

    println("Remaining crew: {ages.len()}")

    # HashMap automatically cleans up when it goes out of scope (RAII)
    return Result.Ok(0)