//! Error cases with byte positions (positions computed with `str::find`, never by hand).

use notescraft_math::{Error, parse};

fn err(src: &str) -> Error {
    match parse(src) {
        Ok(_) => panic!("expected error for {src:?}"),
        Err(e) => e,
    }
}

fn pos_of(src: &str, needle: &str) -> usize {
    src.find(needle).unwrap_or(0)
}

fn unknown(src: &str) {
    let e = err(src);
    let Error::Unknown { pos, .. } = e else { panic!("{src:?}: {e:?}") };
    assert_eq!(pos, pos_of(src, "\\"), "{src:?}");
}

#[test]
fn unknown_commands_carry_backslash_position() {
    unknown("\\frax");
    unknown("a\\foo{b}");
    unknown("\\underbrace");
}

#[test]
fn unbalanced_braces() {
    let e = err("{x");
    let Error::Unbalanced { pos } = e else { panic!("{e:?}") };
    assert_eq!(pos, 0);
    let e = err("\\sqrt{x");
    let Error::Unbalanced { pos } = e else { panic!("{e:?}") };
    assert_eq!(pos, 5);
    let e = err("ab{c{d}");
    let Error::Unbalanced { pos } = e else { panic!("{e:?}") };
    assert_eq!(pos, pos_of("ab{c{d}", "{"));
}

#[test]
fn unexpected_tokens() {
    let e = err("x}");
    let Error::Unexpected { what, pos } = e else { panic!("{e:?}") };
    assert_eq!(what, "}");
    assert_eq!(pos, 1);

    let e = err("a & b");
    let Error::Unexpected { what, pos } = e else { panic!("{e:?}") };
    assert_eq!(what, "&");
    assert_eq!(pos, pos_of("a & b", "&"));
}

#[test]
fn left_right_errors() {
    let e = err("\\left(x");
    let Error::MissingRight { pos } = e else { panic!("{e:?}") };
    assert_eq!(pos, 0);

    let e = err("\\right)");
    let Error::Unexpected { what, .. } = e else { panic!("{e:?}") };
    assert_eq!(what, "\\right outside \\left..\\right");

    let e = err("\\left(x\\right");
    let Error::Unexpected { what, pos } = e else { panic!("{e:?}") };
    assert_eq!(what, "missing delimiter");
    assert_eq!(pos, pos_of("\\left(x\\right", "\\right"));
}

#[test]
fn script_errors() {
    let e = err("x^^y");
    let Error::DoubleScript { pos } = e else { panic!("{e:?}") };
    assert_eq!(pos, 2);

    let e = err("x^");
    let Error::Unexpected { what, pos } = e else { panic!("{e:?}") };
    assert_eq!(what, "missing script argument");
    assert_eq!(pos, 1);

    let e = err("x__y");
    let Error::DoubleScript { pos } = e else { panic!("{e:?}") };
    assert_eq!(pos, 2);
}

#[test]
fn command_argument_errors() {
    let e = err("\\frac{a}");
    let Error::Unexpected { what, pos } = e else { panic!("{e:?}") };
    assert_eq!(what, "missing command argument");
    assert_eq!(pos, 0);

    let e = err("\\hat");
    let Error::Unexpected { what, pos } = e else { panic!("{e:?}") };
    assert_eq!(what, "missing command argument");
    assert_eq!(pos, 0);
}

#[test]
fn environment_errors() {
    let e = err("\\begin{matrix} x \\end{pmatrix}");
    let Error::EnvMismatch { begin, end, pos } = e else { panic!("{e:?}") };
    assert_eq!(begin, "matrix");
    assert_eq!(end, "pmatrix");
    assert_eq!(pos, pos_of("\\begin{matrix} x \\end{pmatrix}", "\\end"));

    let e = err("\\begin{matrix} x");
    let Error::Unbalanced { pos } = e else { panic!("{e:?}") };
    // The unclosed `{` opened at byte 6.
    assert_eq!(pos, 6);

    let e = err("\\begin{qmatrix} x \\end{qmatrix}");
    let Error::Unknown { cmd, pos } = e else { panic!("{e:?}") };
    assert_eq!(cmd, "qmatrix");
    assert_eq!(pos, 0);

    let e = err("\\begin x\\end x");
    match e {
        Error::Unexpected { what, .. } => assert_eq!(what, "\\begin environment name"),
        other => panic!("{other:?}"),
    }
}

#[test]
fn limits_are_bounded() {
    // Depth: 65 nested groups exceed the limit.
    let deep = "{".repeat(65);
    let e = err(&deep);
    let Error::DepthLimit { pos } = e else { panic!("{e:?}") };
    assert_eq!(pos, 64);

    // 63 deep with matching closes parses fine.
    let mut ok = "{".repeat(63);
    ok.push_str(&"}".repeat(63));
    assert!(parse(&ok).is_ok(), "63 deep should parse");
}

#[test]
fn input_cap() {
    let src = "x".repeat(20_001);
    let e = err(&src);
    let Error::TooLong { len } = e else { panic!("{e:?}") };
    assert_eq!(len, 20_001);

    let src = "x".repeat(20_000);
    assert!(parse(&src).is_ok(), "exactly 20000 should parse");
}

#[test]
fn lone_and_escaped_tokens() {
    // `\\` outside an environment: unknown command `\\`.
    let e = err("\\\\");
    let Error::Unknown { cmd, pos } = e else { panic!("{e:?}") };
    assert_eq!(cmd, "\\");
    assert_eq!(pos, 0);

    // Empty input parses to an empty row.
    match parse("") {
        Ok(notescraft_math::Node::Row(list)) => assert_eq!(list, []),
        other => panic!("{other:?}"),
    }
}

#[test]
fn errors_do_not_consume_past_positions() {
    // `αé`: the first non-ASCII source char is rejected (`Unexpected`), and the position
    // is the BYTE offset: `α` spans 2 bytes, so `é`... wait, `α` itself errors first at
    // byte 0. To prove byte offsets, consume multibytes through `\text{}` (legal), then
    // error: the `\\` after `\text{a é}` is at byte 10 (char index 9 would be wrong).
    match parse("αé") {
        Err(Error::Unexpected { what, pos }) => {
            assert_eq!(what, "α");
            assert_eq!(pos, 0);
        }
        other => panic!("{other:?}"),
    }
    let src = "\\text{a é}\\\\foo";
    match parse(src) {
        Err(Error::Unknown { pos, cmd: _ }) => {
            // Byte 11 (the `}` is byte 10, then the first `\\`); a char-index
            // implementation would report 10.
            assert_eq!(pos, pos_of(src, "\\\\foo"));
            assert_eq!(pos, 11);
        }
        other => panic!("{other:?}"),
    }
}

#[test]
fn named_operators_parse() {
    for src in [
        r"\log(xy)=\log x+\log y,\qquad \log\frac{x}{y}=\log x-\log y",
        r"\log_b x=\frac{\ln x}{\ln b}",
        r"\operatorname{Var}(X)=a\bmod b,\ a\equiv 1\pmod{n},\ \iint_D f\,dA\xrightarrow{d}N(0,1)",
        r"\det\begin{pmatrix} a & b \\ c & d \end{pmatrix}=ad-bc",
    ] {
        assert!(parse(src).is_ok(), "{src}");
    }
}