doge-runtime 0.2.0

use std::io::Write;

use crate::error::{DogeError, DogeResult};
use crate::value::Value;

/// `bark x` — print a value on its own line and evaluate to `none`, so
/// `bark` can sit anywhere an expression is expected.
pub fn bark(v: &Value) -> Value {
    println!("{v}");
    Value::None
}

/// `gib()` / `gib("prompt")` — read one line from standard input. An optional
/// prompt, which must be a Str, is written without a trailing newline and flushed
/// first. The returned Str has its trailing newline stripped; at end of input the
/// result is `none`. A stdin read failure is a catchable IOError.
pub fn gib(prompt: Option<&Value>) -> DogeResult {
    if let Some(p) = prompt {
        let text = match p {
            Value::Str(s) => s,
            _ => {
                return Err(DogeError::type_error(format!(
                    "gib needs a Str prompt, got {}",
                    p.describe()
                )))
            }
        };
        print!("{text}");
        let _ = std::io::stdout().flush();
    }
    let mut line = String::new();
    match std::io::stdin().read_line(&mut line) {
        Ok(0) => Ok(Value::None),
        Ok(_) => {
            let line = line.strip_suffix('\n').unwrap_or(&line);
            let line = line.strip_suffix('\r').unwrap_or(line);
            Ok(Value::str(line))
        }
        Err(err) => Err(DogeError::io_error(format!("could not read input: {err}"))),
    }
}

/// `len(x)` — character count for a Str, element count for a List or Dict.
/// Anything else is a catchable type error.
pub fn len(v: &Value) -> DogeResult {
    match v {
        Value::Str(s) => Ok(Value::Int(s.chars().count() as i64)),
        Value::List(items) => Ok(Value::Int(items.borrow().len() as i64)),
        Value::Dict(entries) => Ok(Value::Int(entries.borrow().len() as i64)),
        _ => Err(crate::error::DogeError::type_error(format!(
            "cannot take the len of {}",
            v.describe()
        ))),
    }
}

/// `str(x)` — the value's printed form as a Str. Always succeeds.
pub fn to_str(v: &Value) -> Value {
    Value::str(v.to_string())
}

/// String interpolation (`"a {b} c"`) — join each part's display form, the same
/// text `bark`/`str` would show, into one Str. Always succeeds.
pub fn interp(parts: &[Value]) -> Value {
    let mut out = String::new();
    for part in parts {
        out.push_str(&part.to_string());
    }
    Value::str(out)
}

/// `int(x)` — Int unchanged, Float truncated toward zero, Bool to 0/1, a Str
/// parsed as a whole number. A Str that isn't a number is a catchable
/// `ValueError`; other types are a `TypeError`.
pub fn to_int(v: &Value) -> DogeResult {
    match v {
        Value::Int(n) => Ok(Value::Int(*n)),
        Value::Float(f) => Ok(Value::Int(*f as i64)),
        Value::Bool(b) => Ok(Value::Int(i64::from(*b))),
        Value::Str(s) => s.trim().parse::<i64>().map(Value::Int).map_err(|_| {
            crate::error::DogeError::value_error(format!("cannot turn {s:?} into an Int"))
        }),
        _ => Err(crate::error::DogeError::type_error(format!(
            "cannot turn {} into an Int",
            v.describe()
        ))),
    }
}

/// `float(x)` — Int and Bool widen to Float, Float is unchanged, a numeric Str
/// is parsed. A non-numeric Str is a catchable `ValueError`; other types are a
/// `TypeError`.
pub fn to_float(v: &Value) -> DogeResult {
    match v {
        Value::Int(n) => Ok(Value::Float(*n as f64)),
        Value::Float(f) => Ok(Value::Float(*f)),
        Value::Bool(b) => Ok(Value::Float(if *b { 1.0 } else { 0.0 })),
        Value::Str(s) => s.trim().parse::<f64>().map(Value::Float).map_err(|_| {
            crate::error::DogeError::value_error(format!("cannot turn {s:?} into a Float"))
        }),
        _ => Err(crate::error::DogeError::type_error(format!(
            "cannot turn {} into a Float",
            v.describe()
        ))),
    }
}

/// `range(start, end)` — the Ints `start, start+1, …, end-1` as an eager List.
/// When `end <= start` the List is naturally empty. Both arguments must be Int;
/// anything else is a catchable type error. The one-argument Doge form
/// `range(n)` is compiled as `range(0, n)`, so the runtime has one signature.
pub fn range(start: &Value, end: &Value) -> DogeResult {
    match (start, end) {
        (Value::Int(a), Value::Int(b)) => Ok(Value::list((*a..*b).map(Value::Int).collect())),
        (Value::Int(_), other) | (other, _) => Err(crate::error::DogeError::type_error(format!(
            "range needs Int bounds, got {}",
            other.describe()
        ))),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::error::ErrorKind;

    #[test]
    fn bark_returns_none() {
        assert!(matches!(bark(&Value::str("much hello")), Value::None));
    }

    #[test]
    fn len_counts_characters_and_elements() {
        // Char count, not byte count — 'é' is one character.
        assert!(matches!(len(&Value::str("héllo")).unwrap(), Value::Int(5)));
        assert!(matches!(
            len(&Value::list(vec![Value::Int(1), Value::Int(2)])).unwrap(),
            Value::Int(2)
        ));
        assert_eq!(len(&Value::Int(3)).unwrap_err().kind, ErrorKind::TypeError);
    }

    #[test]
    fn interp_joins_display_forms() {
        let parts = [
            Value::str("age "),
            Value::Int(7),
            Value::str(", "),
            Value::None,
        ];
        assert!(matches!(interp(&parts), Value::Str(s) if &*s == "age 7, none"));
        // Nested Strs embed bare, matching bark/str, not the quoted repr.
        let nested = [Value::str("["), Value::str("hi"), Value::str("]")];
        assert!(matches!(interp(&nested), Value::Str(s) if &*s == "[hi]"));
        assert!(matches!(interp(&[]), Value::Str(s) if s.is_empty()));
    }

    #[test]
    fn conversions_round_trip() {
        assert!(matches!(to_str(&Value::Int(7)), Value::Str(s) if &*s == "7"));
        assert!(matches!(to_int(&Value::Float(3.9)).unwrap(), Value::Int(3)));
        assert!(matches!(
            to_int(&Value::str(" 42 ")).unwrap(),
            Value::Int(42)
        ));
        assert!(matches!(to_float(&Value::Int(4)).unwrap(), Value::Float(f) if f == 4.0));
    }

    #[test]
    fn bad_conversions_are_catchable_value_errors() {
        assert_eq!(
            to_int(&Value::str("dog")).unwrap_err().kind,
            ErrorKind::ValueError
        );
        assert_eq!(
            to_float(&Value::str("woof")).unwrap_err().kind,
            ErrorKind::ValueError
        );
    }

    #[test]
    fn range_two_args() {
        let xs = range(&Value::Int(2), &Value::Int(5)).unwrap();
        match xs {
            Value::List(items) => {
                let items = items.borrow();
                assert_eq!(items.len(), 3);
                assert!(matches!(items[0], Value::Int(2)));
                assert!(matches!(items[2], Value::Int(4)));
            }
            _ => panic!("expected a list"),
        }
    }

    #[test]
    fn range_empty_when_end_not_after_start() {
        let xs = range(&Value::Int(5), &Value::Int(5)).unwrap();
        assert!(matches!(len(&xs).unwrap(), Value::Int(0)));
        let ys = range(&Value::Int(5), &Value::Int(2)).unwrap();
        assert!(matches!(len(&ys).unwrap(), Value::Int(0)));
    }

    #[test]
    fn range_rejects_float() {
        assert_eq!(
            range(&Value::Int(0), &Value::Float(3.0)).unwrap_err().kind,
            ErrorKind::TypeError
        );
        assert_eq!(
            range(&Value::Float(0.0), &Value::Int(3)).unwrap_err().kind,
            ErrorKind::TypeError
        );
    }
}