# Example 04: String Operations
#
# Demonstrates:
# - Two quote styles (double and single quotes)
# - String length and size operations
# - Empty string checking
# - String interpolation for building strings
# - Substring search with Maybe@(T)
# - String splitting into arrays
# - Whitespace trimming
# - Single-quote strings in method arguments
#
# Sushi supports two string literal syntaxes:
# - Double quotes ("..."): Support interpolation with {expr}
# - Single quotes ('...'): Plain literals, no interpolation
#
# Sushi strings are UTF-8 encoded. String concatenation is done via
# interpolation, not the + operator. Many string methods return Result@(T)
# or Maybe@(T) for safe error handling.

use <collections/strings>

fn main() i32:
    let string message = "Don't Panic"
    let string guide_entry = "  Vogon poetry is the third worst in the Universe.  "

    # String.len() returns the number of UTF-8 characters.
    # This may differ from byte count for non-ASCII text.
    println("Message length: {message.len()}")

    # String.size() returns the byte count.
    # For ASCII strings, size == len. For UTF-8, size >= len.
    println("Message size: {message.size()}")

    # String.is_empty() checks if the string has zero length.
    # This is more idiomatic than checking len() == 0.
    let string empty = ""

    if (empty.is_empty()):
        println("String is empty")
    else:
        println("String has content")

    # String concatenation in Sushi uses interpolation, not '+'.
    # Build strings by embedding variables and literals in {}.
    # This is more efficient and readable than operator overloading.
    let string suffix = "Always bring a towel"
    let string full_message = "{message} - {suffix}"
    println(full_message)

    # String.find(substring) searches for the first occurrence.
    # Returns Maybe@(i32) with the index, or Maybe.None() if not found.
    # This demonstrates safe handling of search failure.
    # Note: Single-quote strings work great for method arguments
    let Maybe@(i32) pos = message.find('Panic')

    match pos:
        Maybe.Some(index) ->
            println("Found 'Panic' at position {index}")
        Maybe.None() ->
            println("'Panic' not found")

    # String.split(delimiter) splits a string into a dynamic array.
    # Returns string[] containing all parts between delimiters.
    # Empty strings between consecutive delimiters are included.
    # Single quotes for the delimiter make it clear it's a literal
    let string planets = "Earth,Betelgeuse,Magrathea,Vogsphere"
    let string[] planet_list = planets.split(',')

    println("Planets:")

    # Iterate over the array using .iter() method.
    # foreach loops require an iterator, not the array directly.
    foreach(planet in planet_list.iter()):
        println("  - {planet}")

    # String.trim() removes leading and trailing whitespace.
    # Returns a new string; the original is unchanged (strings are immutable).
    let string trimmed = guide_entry.trim()
    println("Original: '{guide_entry}'")
    println("Trimmed: '{trimmed}'")

    # Convert case (ASCII only)
    let string loud = message.upper()
    let string quiet = message.lower()

    println("Uppercase: {loud}")
    println("Lowercase: {quiet}")

    return Result.Ok(0)