mod atom;

use super::*;
pub(super) use self::atom::literal;

const EXPR_FIRST: TokenSet = UNARY_EXPR_FIRST;

pub(super) fn expr(p: &mut Parser) {
    let r = Restrictions { forbid_structs: false };
    expr_bp(p, r, 1)
}

fn expr_no_struct(p: &mut Parser) {
    let r = Restrictions { forbid_structs: true };
    expr_bp(p, r, 1)
}

// test block
// fn a() {}
// fn b() { let _ = 1; }
// fn c() { 1; 2; }
// fn d() { 1; 2 }
pub(super) fn block(p: &mut Parser) {
    if !p.at(L_CURLY) {
        p.error("expected block");
        return;
    }
    atom::block_expr(p);
}

#[derive(Clone, Copy)]
struct Restrictions {
    forbid_structs: bool
}

// test expr_binding_power
// fn foo() {
//     1 + 2 * 3 == 1 * 2 + 3;
//     *x = 1 + 1;
// }
fn bp_of(op: SyntaxKind) -> u8 {
    match op {
        EQ => 1,
        EQEQ | NEQ => 2,
        MINUS | PLUS => 3,
        STAR | SLASH => 4,
        _ => 0
    }
}

// Parses expression with binding power of at least bp.
fn expr_bp(p: &mut Parser, r: Restrictions, bp: u8) {
    let mut lhs = match unary_expr(p, r) {
        Some(lhs) => lhs,
        None => return,
    };

    loop {
        let op_bp = bp_of(p.current());
        if op_bp < bp {
            break;
        }
        lhs = bin_expr(p, r, lhs, op_bp);
    }
}

const UNARY_EXPR_FIRST: TokenSet =
    token_set_union![
        token_set![AMPERSAND, STAR, EXCL],
        atom::ATOM_EXPR_FIRST,
    ];

fn unary_expr(p: &mut Parser, r: Restrictions) -> Option<CompletedMarker> {
    let m;
    let kind = match p.current() {
        // test ref_expr
        // fn foo() {
        //     let _ = &1;
        //     let _ = &mut &f();
        // }
        AMPERSAND => {
            m = p.start();
            p.bump();
            p.eat(MUT_KW);
            REF_EXPR

        },
        // test deref_expr
        // fn foo() {
        //     **&1;
        // }
        STAR => {
            m = p.start();
            p.bump();
            DEREF_EXPR
        },
        // test not_expr
        // fn foo() {
        //     !!true;
        // }
        EXCL => {
            m = p.start();
            p.bump();
            NOT_EXPR
        },
        _ => {
            let lhs = atom::atom_expr(p, r)?;
            return Some(postfix_expr(p, lhs))
        }
    };
    unary_expr(p, r);
    Some(m.complete(p, kind))
}

fn postfix_expr(p: &mut Parser, mut lhs: CompletedMarker) -> CompletedMarker {
    loop {
        lhs = match p.current() {
            L_PAREN => call_expr(p, lhs),
            DOT if p.nth(1) == IDENT => if p.nth(2) == L_PAREN {
                method_call_expr(p, lhs)
            } else {
                field_expr(p, lhs)
            },
            DOT if p.nth(1) == INT_NUMBER => field_expr(p, lhs),
            QUESTION => try_expr(p, lhs),
            _ => break,
        }
    }
    lhs
}

// test call_expr
// fn foo() {
//     let _ = f();
//     let _ = f()(1)(1, 2,);
// }
fn call_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
    assert!(p.at(L_PAREN));
    let m = lhs.precede(p);
    arg_list(p);
    m.complete(p, CALL_EXPR)
}

// test method_call_expr
// fn foo() {
//     x.foo();
//     y.bar(1, 2,);
// }
fn method_call_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
    assert!(p.at(DOT) && p.nth(1) == IDENT && p.nth(2) == L_PAREN);
    let m = lhs.precede(p);
    p.bump();
    name_ref(p);
    arg_list(p);
    m.complete(p, METHOD_CALL_EXPR)
}

// test field_expr
// fn foo() {
//     x.foo;
//     x.0.bar;
// }
fn field_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
    assert!(p.at(DOT) && (p.nth(1) == IDENT || p.nth(1) == INT_NUMBER));
    let m = lhs.precede(p);
    p.bump();
    if p.at(IDENT) {
        name_ref(p)
    } else {
        p.bump()
    }
    m.complete(p, FIELD_EXPR)
}

// test try_expr
// fn foo() {
//     x?;
// }
fn try_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
    assert!(p.at(QUESTION));
    let m = lhs.precede(p);
    p.bump();
    m.complete(p, TRY_EXPR)
}

fn arg_list(p: &mut Parser) {
    assert!(p.at(L_PAREN));
    let m = p.start();
    p.bump();
    while !p.at(R_PAREN) && !p.at(EOF) {
        expr(p);
        if !p.at(R_PAREN) && !p.expect(COMMA) {
            break;
        }
    }
    p.eat(R_PAREN);
    m.complete(p, ARG_LIST);
}

// test path_expr
// fn foo() {
//     let _ = a;
//     let _ = a::b;
//     let _ = ::a::<b>;
// }
fn path_expr(p: &mut Parser, r: Restrictions) -> CompletedMarker {
    assert!(paths::is_path_start(p));
    let m = p.start();
    paths::expr_path(p);
    if p.at(L_CURLY) && !r.forbid_structs {
        struct_lit(p);
        m.complete(p, STRUCT_LIT)
    } else {
        m.complete(p, PATH_EXPR)
    }
}

// test struct_lit
// fn foo() {
//     S {};
//     S { x, y: 32, };
//     S { x, y: 32, ..Default::default() };
// }
fn struct_lit(p: &mut Parser) {
    assert!(p.at(L_CURLY));
    p.bump();
    while !p.at(EOF) && !p.at(R_CURLY) {
        match p.current() {
            IDENT => {
                let m = p.start();
                name_ref(p);
                if p.eat(COLON) {
                    expr(p);
                }
                m.complete(p, STRUCT_LIT_FIELD);
            }
            DOTDOT => {
                p.bump();
                expr(p);
            }
            _ => p.err_and_bump("expected identifier"),
        }
        if !p.at(R_CURLY) {
            p.expect(COMMA);
        }
    }
    p.expect(R_CURLY);
}

fn bin_expr(p: &mut Parser, r: Restrictions, lhs: CompletedMarker, bp: u8) -> CompletedMarker {
    assert!(match p.current() {
        MINUS | PLUS | STAR | SLASH | EQEQ | NEQ | EQ => true,
        _ => false,
    });
    let m = lhs.precede(p);
    p.bump();
    expr_bp(p, r, bp);
    m.complete(p, BIN_EXPR)
}