// See also: file:///usr/share/doc/python/html/reference/grammar.html?highlight=grammar
// See also: https://github.com/antlr/grammars-v4/blob/master/python3/Python3.g4
// See also: file:///usr/share/doc/python/html/reference/compound_stmts.html#function-definitions
// See also: https://greentreesnakes.readthedocs.io/en/latest/nodes.html#keyword

use std::iter::FromIterator;

use crate::ast;
use crate::fstring::parse_located_fstring;
use crate::function::{ArgumentList, parse_args, parse_params};
use crate::error::LexicalError;
use crate::lexer;

use num_bigint::BigInt;

grammar;

// This is a hack to reduce the amount of lalrpop tables generated:
// For each public entry point, a full parse table is generated.
// By having only a single pub function, we reduce this to one.
pub Top: ast::Mod = {
    StartModule <body:Program> => ast::Mod::Module { body, type_ignores: vec![] },
    StartInteractive <body:Program> => ast::Mod::Interactive { body },
    StartExpression <body:TestList> ("\n")* => ast::Mod::Expression { body: Box::new(body) },
};

Program: ast::Suite = {
    <lines:FileLine*> => {
        lines.into_iter().flatten().collect()
    },
};

// A file line either has a declaration, or an empty newline:
FileLine: ast::Suite = {
    Statement,
    "\n" => vec![],
};

Suite: ast::Suite = {
    SimpleStatement,
    "\n" Indent <s:Statement+> Dedent => s.into_iter().flatten().collect(),
};

Statement: ast::Suite = {
    SimpleStatement,
    <s:CompoundStatement> => vec![s],
};

SimpleStatement: ast::Suite = {
    <s1:SmallStatement> <s2:(";" SmallStatement)*> ";"? "\n" => {
        let mut statements = vec![s1];
        statements.extend(s2.into_iter().map(|e| e.1));
        statements
    }
};

SmallStatement: ast::Stmt = {
    ExpressionStatement,
    PassStatement,
    DelStatement,
    FlowStatement,
    ImportStatement,
    GlobalStatement,
    NonlocalStatement,
    AssertStatement,
};

PassStatement: ast::Stmt = {
    <location:@L> "pass" => {
        ast::Stmt {
            location,
            custom: (),
            node: ast::StmtKind::Pass,
        }
    },
};

DelStatement: ast::Stmt = {
    <location:@L> "del" <targets:ExpressionList2> => {
        ast::Stmt {
            location,
            custom: (),
            node: ast::StmtKind::Delete { targets },
        }
    },
};

ExpressionStatement: ast::Stmt = {
    <location:@L> <expression:TestOrStarExprList> <suffix:AssignSuffix*> => {
        // Just an expression, no assignment:
        if suffix.is_empty() {
            ast::Stmt {
                custom: (),
                location,
                node: ast::StmtKind::Expr { value: Box::new(expression) }
            }
        } else {
            let mut targets = vec![expression];
            let mut values = suffix;

            while values.len() > 1 {
                targets.push(values.remove(0));
            }

            let value = Box::new(values.into_iter().next().unwrap());

            ast::Stmt {
                custom: (),
                location,
                node: ast::StmtKind::Assign { targets, value, type_comment: None },
            }
        }
    },
    <location:@L> <target:TestOrStarExprList> <op:AugAssign> <rhs:TestListOrYieldExpr> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::AugAssign {
                target: Box::new(target),
                op,
                value: Box::new(rhs)
            },
        }
    },
    <location:@L> <target:Test> ":" <annotation:Test> <rhs:AssignSuffix?> => {
        let simple = matches!(target.node, ast::ExprKind::Name { .. });
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::AnnAssign {
                target: Box::new(target),
                annotation: Box::new(annotation),
                value: rhs.map(Box::new),
                simple,
            },
        }
    },
};

AssignSuffix: ast::Expr = {
    "=" <e:TestListOrYieldExpr> => e
};

TestListOrYieldExpr: ast::Expr = {
    TestList,
    YieldExpr
}

#[inline]
TestOrStarExprList: ast::Expr = {
    // as far as I can tell, these were the same
    TestList
};

TestOrStarNamedExprList: ast::Expr = {
    GenericList<TestOrStarNamedExpr>
};

TestOrStarExpr: ast::Expr = {
    Test,
    StarExpr,
};

TestOrStarNamedExpr: ast::Expr = {
    NamedExpressionTest,
    StarExpr,
};

AugAssign: ast::Operator = {
    "+=" => ast::Operator::Add,
    "-=" => ast::Operator::Sub,
    "*=" => ast::Operator::Mult,
    "@=" => ast::Operator::MatMult,
    "/=" => ast::Operator::Div,
    "%=" => ast::Operator::Mod,
    "&=" => ast::Operator::BitAnd,
    "|=" => ast::Operator::BitOr,
    "^=" => ast::Operator::BitXor,
    "<<=" => ast::Operator::LShift,
    ">>=" => ast::Operator::RShift,
    "**=" => ast::Operator::Pow,
    "//=" => ast::Operator::FloorDiv,
};

FlowStatement: ast::Stmt = {
    <location:@L> "break" => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Break,
        }
    },
    <location:@L> "continue" => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Continue,
        }
    },
    <location:@L> "return" <value:TestList?> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Return { value: value.map(Box::new) },
        }
    },
    <location:@L> <expression:YieldExpr> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Expr { value: Box::new(expression) },
        }
    },
    RaiseStatement,
};

RaiseStatement: ast::Stmt = {
    <location:@L> "raise" => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Raise { exc: None, cause: None },
        }
    },
    <location:@L> "raise" <t:Test> <c:("from" Test)?> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Raise { exc: Some(Box::new(t)), cause: c.map(|x| Box::new(x.1)) },
        }
    },
};

ImportStatement: ast::Stmt = {
    <location:@L> "import" <names: OneOrMore<ImportAsAlias<DottedName>>> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Import { names },
        }
    },
    <location:@L> "from" <source:ImportFromLocation> "import" <names: ImportAsNames> => {
        let (level, module) = source;
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::ImportFrom {
                level,
                module,
                names
            },
        }
    },
};

ImportFromLocation: (usize, Option<String>) = {
    <dots: ImportDots*> <name:DottedName> => {
        (dots.iter().sum(), Some(name))
    },
    <dots: ImportDots+> => {
        (dots.iter().sum(), None)
    },
};

ImportDots: usize = {
    "..." => 3,
    "." => 1,
};

ImportAsNames: Vec<ast::Alias> = {
    <i:OneOrMore<ImportAsAlias<Identifier>>> => i,
    "(" <i:OneOrMore<ImportAsAlias<Identifier>>> ","? ")" => i,
    "*" => {
        // Star import all
        vec![ast::Alias { name: "*".to_string(), asname: None }]
    },
};


#[inline]
ImportAsAlias<I>: ast::Alias = {
    <name:I> <a: ("as" Identifier)?> => ast::Alias { name, asname: a.map(|a| a.1) },
};

// A name like abc or abc.def.ghi
DottedName: String = {
    <n:name> => n,
    <n:name> <n2: ("." Identifier)+>  => {
        let mut r = n.to_string();
        for x in n2 {
            r.push_str(".");
            r.push_str(&x.1);
        }
        r
    },
};

GlobalStatement: ast::Stmt = {
    <location:@L> "global" <names:OneOrMore<Identifier>> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Global { names }
        }
    },
};

NonlocalStatement: ast::Stmt = {
    <location:@L> "nonlocal" <names:OneOrMore<Identifier>> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Nonlocal { names }
        }
    },
};

AssertStatement: ast::Stmt = {
    <location:@L> "assert" <test:Test> <msg: ("," Test)?> => {
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Assert {
                test: Box::new(test),
                msg: msg.map(|e| Box::new(e.1))
            }
        }
    },
};

CompoundStatement: ast::Stmt = {
    IfStatement,
    WhileStatement,
    ForStatement,
    TryStatement,
    WithStatement,
    FuncDef,
    ClassDef,
};

IfStatement: ast::Stmt = {
    <location:@L> "if" <test:NamedExpressionTest> ":" <body:Suite> <s2:(@L "elif" NamedExpressionTest ":" Suite)*> <s3:("else" ":" Suite)?> => {
        // Determine last else:
        let mut last = s3.map(|s| s.2).unwrap_or_default();

        // handle elif:
        for i in s2.into_iter().rev() {
            let x = ast::Stmt {
                custom: (),
                location: i.0,
                node: ast::StmtKind::If { test: Box::new(i.2), body: i.4, orelse: last },
            };
            last = vec![x];
        }

        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::If { test: Box::new(test), body, orelse: last }
        }
    },
};

WhileStatement: ast::Stmt = {
    <location:@L> "while" <test:NamedExpressionTest> ":" <body:Suite> <s2:("else" ":" Suite)?> => {
        let orelse = s2.map(|s| s.2).unwrap_or_default();
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::While {
                test: Box::new(test),
                body,
                orelse
            },
        }
    },
};

ForStatement: ast::Stmt = {
    <location:@L> <is_async:"async"?> "for" <target:ExpressionList> "in" <iter:TestList> ":" <body:Suite> <s2:("else" ":" Suite)?> => {
        let orelse = s2.map(|s| s.2).unwrap_or_default();
        let target = Box::new(target);
        let iter = Box::new(iter);
        let type_comment = None;
        let node = if is_async.is_some() {
            ast::StmtKind::AsyncFor { target, iter, body, orelse, type_comment }
        } else {
            ast::StmtKind::For { target, iter, body, orelse, type_comment }
        };
        ast::Stmt::new(location, node)
    },
};

TryStatement: ast::Stmt = {
    <location:@L> "try" ":" <body:Suite> <handlers:ExceptClause+> <else_suite:("else" ":" Suite)?> <finally:("finally" ":" Suite)?> => {
        let orelse = else_suite.map(|s| s.2).unwrap_or_default();
        let finalbody = finally.map(|s| s.2).unwrap_or_default();
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Try {
                body,
                handlers,
                orelse,
                finalbody,
            },
        }
    },
    <location:@L> "try" ":" <body:Suite> <finally:("finally" ":" Suite)> => {
        let handlers = vec![];
        let orelse = vec![];
        let finalbody = finally.2;
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::Try {
                body,
                handlers,
                orelse,
                finalbody,
            },
        }
    },
};

ExceptClause: ast::Excepthandler = {
    <location:@L> "except" <typ:Test?> ":" <body:Suite> => {
        ast::Excepthandler::new(
            location,
            ast::ExcepthandlerKind::ExceptHandler {
                type_: typ.map(Box::new),
                name: None,
                body,
            },
        )
    },
    <location:@L> "except" <x:(Test "as" Identifier)> ":" <body:Suite> => {
        ast::Excepthandler::new(
            location,
            ast::ExcepthandlerKind::ExceptHandler {
                type_: Some(Box::new(x.0)),
                name: Some(x.2),
                body,
            },
        )
    },
};

WithStatement: ast::Stmt = {
    <location:@L> <is_async:"async"?> "with" <items:OneOrMore<WithItem>> ":" <body:Suite> => {
        let type_comment = None;
        let node = if is_async.is_some() {
            ast::StmtKind::AsyncWith { items, body, type_comment }
        } else {
            ast::StmtKind::With { items, body, type_comment }
        };
        ast::Stmt::new(location, node)
    },
};

WithItem: ast::Withitem = {
    <context_expr:Test> <n:("as" Expression)?> => {
        let optional_vars = n.map(|val| Box::new(val.1));
        let context_expr = Box::new(context_expr);
        ast::Withitem { context_expr, optional_vars }
    },
};

FuncDef: ast::Stmt = {
    <decorator_list:Decorator*> <location:@L> <is_async:"async"?> "def" <name:Identifier> <args:Parameters> <r:("->" Test)?> ":" <body:Suite> => {
        let args = Box::new(args);
        let returns = r.map(|x| Box::new(x.1));
        let type_comment = None;
        let node = if is_async.is_some() {
            ast::StmtKind::AsyncFunctionDef { name, args, body, decorator_list, returns, type_comment }
        } else {
            ast::StmtKind::FunctionDef { name, args, body, decorator_list, returns, type_comment }
        };
        ast::Stmt::new(location, node)
    },
};

Parameters: ast::Arguments = {
    "(" <a: (ParameterList<TypedParameter>)?> ")" => {
        a.unwrap_or_else(|| ast::Arguments {
            posonlyargs: vec![],
            args: vec![],
            vararg: None,
            kwonlyargs: vec![],
            kw_defaults: vec![],
            kwarg: None,
            defaults: vec![]
        })
    }
};

// Note that this is a macro which is used once for function defs, and
// once for lambda defs.
ParameterList<ArgType>: ast::Arguments = {
    <param1:ParameterDefs<ArgType>> <args2:("," ParameterListStarArgs<ArgType>)?> ","? =>? {
        let (posonlyargs, args, defaults) = parse_params(param1)?;

        // Now gather rest of parameters:
        let (vararg, kwonlyargs, kw_defaults, kwarg) = args2.map_or((None, vec![], vec![], None), |x| x.1);

        Ok(ast::Arguments {
            posonlyargs,
            args,
            kwonlyargs,
            vararg,
            kwarg,
            defaults,
            kw_defaults,
        })
    },
    <param1:ParameterDefs<ArgType>> <kw:("," KwargParameter<ArgType>)> ","? =>? {
        let (posonlyargs, args, defaults) = parse_params(param1)?;

        // Now gather rest of parameters:
        let vararg = None;
        let kwonlyargs = vec![];
        let kw_defaults = vec![];
        let kwarg = kw.1;

        Ok(ast::Arguments {
            posonlyargs,
            args,
            kwonlyargs,
            vararg,
            kwarg,
            defaults,
            kw_defaults,
        })
    },
    <params:ParameterListStarArgs<ArgType>> ","? => {
        let (vararg, kwonlyargs, kw_defaults, kwarg) = params;
        ast::Arguments {
            posonlyargs: vec![],
            args: vec![],
            kwonlyargs,
            vararg,
            kwarg,
            defaults: vec![],
            kw_defaults,
        }
    },
    <kwarg:KwargParameter<ArgType>> ","? => {
        ast::Arguments {
            posonlyargs: vec![],
            args: vec![],
            kwonlyargs: vec![],
            vararg: None,
            kwarg,
            defaults: vec![],
            kw_defaults: vec![],
        }
    },
};

// Use inline here to make sure the "," is not creating an ambiguity.
#[inline]
ParameterDefs<ArgType>: (Vec<(ast::Arg, Option<ast::Expr>)>, Vec<(ast::Arg, Option<ast::Expr>)>) = {
    <args:OneOrMore<ParameterDef<ArgType>>> => {
        (vec![], args)
    },
    <pos_args:OneOrMore<ParameterDef<ArgType>>> "," "/" <args:("," ParameterDef<ArgType>)*>  => {
        (pos_args, args.into_iter().map(|e| e.1).collect())
    },
};

ParameterDef<ArgType>: (ast::Arg, Option<ast::Expr>) = {
    <i:ArgType> => (i, None),
    <i:ArgType> "=" <e:Test> => (i, Some(e)),
};

UntypedParameter: ast::Arg = {
    <location:@L> <arg:Identifier> => ast::Arg::new(
        location,
        ast::ArgData { arg, annotation: None, type_comment: None },
    ),
};

TypedParameter: ast::Arg = {
    <location:@L> <arg:Identifier> <a:(":" Test)?>=> {
        let annotation = a.map(|x| Box::new(x.1));
        ast::Arg::new(location, ast::ArgData { arg, annotation, type_comment: None })
    },
};

// Use inline here to make sure the "," is not creating an ambiguity.
// TODO: figure out another grammar that makes this inline no longer required.
#[inline]
ParameterListStarArgs<ArgType>: (Option<Box<ast::Arg>>, Vec<ast::Arg>, Vec<Option<Box<ast::Expr>>>, Option<Box<ast::Arg>>) = {
    "*" <va:ArgType?> <kw:("," ParameterDef<ArgType>)*> <kwarg:("," KwargParameter<ArgType>)?> => {
        // Extract keyword arguments:
        let mut kwonlyargs = vec![];
        let mut kw_defaults = vec![];
        for (name, value) in kw.into_iter().map(|x| x.1) {
            kwonlyargs.push(name);
            kw_defaults.push(value.map(Box::new));
        }

        let kwarg = kwarg.map(|n| n.1).flatten();
        let va = va.map(Box::new);

        (va, kwonlyargs, kw_defaults, kwarg)
    }
};

KwargParameter<ArgType>: Option<Box<ast::Arg>> = {
    "**" <kwarg:ArgType?> => {
        kwarg.map(Box::new)
    }
};

ClassDef: ast::Stmt = {
    <decorator_list:Decorator*> <location:@L> "class" <name:Identifier> <a:("(" ArgumentList ")")?> ":" <body:Suite> => {
        let (bases, keywords) = match a {
            Some((_, arg, _)) => (arg.args, arg.keywords),
            None => (vec![], vec![]),
        };
        ast::Stmt {
            custom: (),
            location,
            node: ast::StmtKind::ClassDef {
                name,
                bases,
                keywords,
                body,
                decorator_list,
            },
        }
    },
};

// Decorators:
Decorator: ast::Expr = {
    <location:@L>"@" <p:Test> "\n" => {
        p
    },
};

YieldExpr: ast::Expr = {
    <location:@L> "yield" <value:TestList?> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::Yield { value: value.map(Box::new) }
    },
    <location:@L> "yield" "from" <e:Test> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::YieldFrom { value: Box::new(e) }
    },
};

Test: ast::Expr = {
    <expr:OrTest> <condition: (@L "if" OrTest "else" Test)?> => {
        if let Some(c) = condition {
            ast::Expr {
                location: c.0,
                custom: (),
                node: ast::ExprKind::IfExp {
                    test: Box::new(c.2),
                    body: Box::new(expr),
                    orelse: Box::new(c.4),
                }
            }
        } else {
            expr
        }
    },
    LambdaDef,
};

NamedExpressionTest: ast::Expr = {
    <location:@L><left: (Identifier ":=")?> <right:Test> => {
        if let Some(l) = left {
            ast::Expr {
                location: location,
                custom: (),
                node: ast::ExprKind::NamedExpr {
                    target: Box::new(ast::Expr::new(
                        location,
                        ast::ExprKind::Name { id: l.0, ctx: ast::ExprContext::Store },
                    )),
                    value: Box::new(right),
                }
            }
        } else {
            right
        }
    }
}

LambdaDef: ast::Expr = {
    <location:@L> "lambda" <p:ParameterList<UntypedParameter>?> ":" <body:Test> => {
        let p = p.unwrap_or_else(|| {
            ast::Arguments {
                posonlyargs: vec![],
                args: vec![],
                vararg: None,
                kwonlyargs: vec![],
                kw_defaults: vec![],
                kwarg: None,
                defaults: vec![]
            }
        });
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::Lambda {
                args: Box::new(p),
                body: Box::new(body)
            }
        }
    }
}

OrTest: ast::Expr = {
    <e1:AndTest> <location:@L> <e2:("or" AndTest)*> => {
        if e2.is_empty() {
            e1
        } else {
            let mut values = vec![e1];
            values.extend(e2.into_iter().map(|e| e.1));
            ast::Expr {
                location,
                custom: (),
                node: ast::ExprKind::BoolOp { op: ast::Boolop::Or, values }
            }
        }
    },
};

AndTest: ast::Expr = {
    <e1:NotTest> <location:@L> <e2:("and" NotTest)*> => {
        if e2.is_empty() {
            e1
        } else {
            let mut values = vec![e1];
            values.extend(e2.into_iter().map(|e| e.1));
            ast::Expr {
                location,
                custom: (),
                node: ast::ExprKind::BoolOp { op: ast::Boolop::And, values }
            }
        }
    },
};

NotTest: ast::Expr = {
    <location:@L> "not" <e:NotTest> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::UnaryOp { operand: Box::new(e), op: ast::Unaryop::Not }
    },
    Comparison,
};

Comparison: ast::Expr = {
    <left:Expression> <location:@L> <comparisons:(CompOp Expression)+> => {
        let (ops, comparators) = comparisons.into_iter().unzip();
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::Compare { left: Box::new(left), ops, comparators }
        }
    },
    Expression,
};

CompOp: ast::Cmpop = {
    "==" => ast::Cmpop::Eq,
    "!=" => ast::Cmpop::NotEq,
    "<" => ast::Cmpop::Lt,
    "<=" => ast::Cmpop::LtE,
    ">" => ast::Cmpop::Gt,
    ">=" => ast::Cmpop::GtE,
    "in" => ast::Cmpop::In,
    "not" "in" => ast::Cmpop::NotIn,
    "is" => ast::Cmpop::Is,
    "is" "not" => ast::Cmpop::IsNot,
};

Expression: ast::Expr = {
    <e1:Expression> <location:@L> "|" <e2:XorExpression> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::BinOp { left: Box::new(e1), op: ast::Operator::BitOr, right: Box::new(e2) }
    },
    XorExpression,
};

XorExpression: ast::Expr = {
    <e1:XorExpression> <location:@L> "^" <e2:AndExpression> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::BinOp { left: Box::new(e1), op: ast::Operator::BitXor, right: Box::new(e2) }
    },
    AndExpression,
};

AndExpression: ast::Expr = {
    <e1:AndExpression> <location:@L> "&" <e2:ShiftExpression> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::BinOp { left: Box::new(e1), op: ast::Operator::BitAnd, right: Box::new(e2) }
    },
    ShiftExpression,
};

ShiftExpression: ast::Expr = {
    <e1:ShiftExpression> <location:@L> <op:ShiftOp> <e2:ArithmaticExpression> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::BinOp { left: Box::new(e1), op, right: Box::new(e2) }
    },
    ArithmaticExpression,
};

ShiftOp: ast::Operator = {
    "<<" => ast::Operator::LShift,
    ">>" => ast::Operator::RShift,
};

ArithmaticExpression: ast::Expr = {
    <a:ArithmaticExpression> <location:@L> <op:AddOp> <b:Term> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::BinOp { left: Box::new(a), op, right: Box::new(b) }
    },
    Term,
};

AddOp: ast::Operator = {
    "+" => ast::Operator::Add,
    "-" => ast::Operator::Sub,
};

Term: ast::Expr = {
    <a:Term> <location:@L> <op:MulOp> <b:Factor> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::BinOp { left: Box::new(a), op, right: Box::new(b) }
    },
    Factor,
};

MulOp: ast::Operator = {
    "*" => ast::Operator::Mult,
    "/" => ast::Operator::Div,
    "//" => ast::Operator::FloorDiv,
    "%" => ast::Operator::Mod,
    "@" => ast::Operator::MatMult,
};

Factor: ast::Expr = {
    <location:@L> <op:UnaryOp> <e:Factor> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::UnaryOp { operand: Box::new(e), op }
    },
    Power,
};

UnaryOp: ast::Unaryop = {
    "+" => ast::Unaryop::UAdd,
    "-" => ast::Unaryop::USub,
    "~" => ast::Unaryop::Invert,
};

Power: ast::Expr = {
    <e:AtomExpr> <e2:(@L "**" Factor)?> => {
        match e2 {
            None => e,
            Some((location, _, b)) => ast::Expr {
                location,
                custom: (),
                node: ast::ExprKind::BinOp { left: Box::new(e), op: ast::Operator::Pow, right: Box::new(b) }
            },
        }
    }
};

AtomExpr: ast::Expr = {
    <location:@L> <is_await:"await"?> <atom:AtomExpr2> => {
        if is_await.is_some() {
            ast::Expr {
                location,
                custom: (),
                node: ast::ExprKind::Await { value: Box::new(atom) }
            }
        } else {
            atom
        }
    }
}

AtomExpr2: ast::Expr = {
    Atom,
    <f:AtomExpr2> <location:@L> "(" <a:ArgumentList> ")" => {
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::Call { func: Box::new(f), args: a.args, keywords: a.keywords }
        }
    },
    <e:AtomExpr2> <location:@L> "[" <s:SubscriptList> "]" => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::Subscript { value: Box::new(e), slice: Box::new(s), ctx: ast::ExprContext::Load }
    },
    <e:AtomExpr2> <location:@L> "." <attr:Identifier> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::Attribute { value: Box::new(e), attr, ctx: ast::ExprContext::Load }
    },
};

SubscriptList: ast::Expr = {
    <location:@L> <s1:Subscript> <s2:("," Subscript)*> ","? => {
        if s2.is_empty() {
            s1
        } else {
            let mut dims = vec![s1];
            for x in s2 {
                dims.push(x.1)
            }

            ast::Expr {
                location,
                custom: (),
                node: ast::ExprKind::Tuple { elts: dims, ctx: ast::ExprContext::Load },
            }
        }
    }
};

Subscript: ast::Expr = {
    Test,
    <e1:Test?> <location:@L> ":" <e2:Test?> <e3:SliceOp?> => {
        let lower = e1.map(Box::new);
        let upper = e2.map(Box::new);
        let step = e3.flatten().map(Box::new);
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::Slice { lower, upper, step }
        }
    }
};

SliceOp: Option<ast::Expr> = {
    <location:@L> ":" <e:Test?> => e,
}

Atom: ast::Expr = {
    <location:@L> <s:(@L string)+> =>? {
        let values = s.into_iter().map(|(loc, (value, is_fstring))| {
            if is_fstring {
                parse_located_fstring(&value, loc)
            } else {
                Ok(ast::Expr::new(
                    loc,
                    ast::ExprKind::Constant { value: value.into(), kind: None },
                ))
            }
        });
        let values = values.collect::<Result<Vec<_>, _>>()?;

        Ok(if values.len() > 1 {
            ast::Expr::new(location, ast::ExprKind::JoinedStr { values })
        } else {
            values.into_iter().next().unwrap()
        })
    },
    <location:@L> <value:Constant> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::Constant { value, kind: None }
    },
    <location:@L> <name:Identifier> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::Name { id: name, ctx: ast::ExprContext::Load }
    },
    <location:@L> "[" <e:ListLiteralValues?> "]" => {
        let elts = e.unwrap_or_default();
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::List { elts, ctx: ast::ExprContext::Load }
        }
    },
    <location:@L> "[" <elt:TestOrStarNamedExpr> <generators:CompFor> "]" => {
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::ListComp { elt: Box::new(elt), generators }
        }
    },
    <location:@L> "(" <elements:TestOrStarNamedExprList?> ")" => {
        elements.unwrap_or(ast::Expr {
             location,
             custom: (),
             node: ast::ExprKind::Tuple { elts: Vec::new(), ctx: ast::ExprContext::Load }
        })
    },
    "(" <e:YieldExpr> ")" => e,
    <location:@L> "(" <elt:Test> <generators:CompFor> ")" => {
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::GeneratorExp { elt: Box::new(elt), generators }
        }
    },
    <location:@L> "{" <e:DictLiteralValues?> "}" => {
        let (keys, values) = e.unwrap_or_default();
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::Dict { keys, values }
        }
    },
    <location:@L> "{" <e1:DictEntry> <generators:CompFor> "}" => {
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::DictComp {
                key: Box::new(e1.0),
                value: Box::new(e1.1),
                generators,
            }
        }
    },
    <location:@L> "{" <elts:SetLiteralValues> "}" => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::Set { elts }
    },
    <location:@L> "{" <elt:Test> <generators:CompFor> "}" => {
        ast::Expr {
            location,
            custom: (),
            node: ast::ExprKind::SetComp { elt: Box::new(elt), generators }
        }
    },
    <location:@L> "True" => ast::Expr::new(location, ast::ExprKind::Constant { value: true.into(), kind: None }),
    <location:@L> "False" => ast::Expr::new(location, ast::ExprKind::Constant { value: false.into(), kind: None }),
    <location:@L> "None" => ast::Expr::new(location, ast::ExprKind::Constant { value: ast::Constant::None, kind: None }),
    <location:@L> "..." => ast::Expr::new(location, ast::ExprKind::Constant { value: ast::Constant::Ellipsis, kind: None }),
};

ListLiteralValues: Vec<ast::Expr> = {
    <e:OneOrMore<TestOrStarNamedExpr>> ","? => e,
};

DictLiteralValues: (Vec<Option<Box<ast::Expr>>>, Vec<ast::Expr>) = {
    <elements:OneOrMore<DictElement>> ","? => elements.into_iter().unzip(),
};

DictEntry: (ast::Expr, ast::Expr) = {
    <e1: Test> ":" <e2: Test> => (e1, e2),
};

DictElement: (Option<Box<ast::Expr>>, ast::Expr) = {
    <e:DictEntry> => (Some(Box::new(e.0)), e.1),
    "**" <e:Expression> => (None, e),
};

SetLiteralValues: Vec<ast::Expr> = {
    <e1:OneOrMore<TestOrStarNamedExpr>> ","? => e1
};

ExpressionOrStarExpression = {
    Expression,
    StarExpr
};

ExpressionList: ast::Expr = {
    GenericList<ExpressionOrStarExpression>
};

ExpressionList2: Vec<ast::Expr> = {
    <elements:OneOrMore<Expression>> ","? => elements,
};

// A test list is one of:
// - a list of expressions
// - a single expression
// - a single expression followed by a trailing comma
#[inline]
TestList: ast::Expr = {
    GenericList<TestOrStarExpr>
};

GenericList<Element>: ast::Expr = {
    <location:@L> <elts:OneOrMore<Element>> <trailing_comma:","?> => {
        if elts.len() == 1 && trailing_comma.is_none() {
            elts.into_iter().next().unwrap()
        } else {
            ast::Expr {
                location,
                custom: (),
                node: ast::ExprKind::Tuple { elts, ctx: ast::ExprContext::Load }
            }
        }
    }
}

// Test
StarExpr: ast::Expr = {
    <location:@L> "*" <e:Expression> => ast::Expr {
        location,
        custom: (),
        node: ast::ExprKind::Starred { value: Box::new(e), ctx: ast::ExprContext::Load },
    }
};

// Comprehensions:
CompFor: Vec<ast::Comprehension> = <c:SingleForComprehension+> => c;

SingleForComprehension: ast::Comprehension = {
    <location:@L> <is_async:"async"?> "for" <target:ExpressionList> "in" <iter:OrTest> <ifs:ComprehensionIf*> => {
        let is_async = is_async.is_some();
        ast::Comprehension {
            target: Box::new(target),
            iter: Box::new(iter),
            ifs,
            is_async
        }
    }
};

ExpressionNoCond: ast::Expr = OrTest;
ComprehensionIf: ast::Expr = "if" <c:ExpressionNoCond> => c;

ArgumentList: ArgumentList = {
    <e: Comma<FunctionArgument>> =>? {
        let arg_list = parse_args(e)?;
        Ok(arg_list)
    }
};

FunctionArgument: (Option<(ast::Location, Option<String>)>, ast::Expr) = {
    <e:NamedExpressionTest> <c:CompFor?> => {
        let expr = match c {
            Some(c) => ast::Expr {
                location: e.location,
                custom: (),
                node: ast::ExprKind::GeneratorExp {
                    elt: Box::new(e),
                    generators: c,
                }
            },
            None => e,
        };
        (None, expr)
    },
    <location:@L> <i:Identifier> "=" <e:Test> => (Some((location, Some(i))), e),
    <location:@L> "*" <e:Test> => {
        let expr = ast::Expr::new(
            location,
            ast::ExprKind::Starred { value: Box::new(e), ctx: ast::ExprContext::Load },
        );
        (None, expr)
    },
    <location:@L> "**" <e:Test> => (Some((location, None)), e),
};

#[inline]
Comma<T>: Vec<T> = {
    <items: (<T> ",")*> <last: T?> => {
        let mut items = items;
        items.extend(last);
        items
    }
};

#[inline]
OneOrMore<T>: Vec<T> = {
    <i1: T> <i2:("," T)*> => {
        let mut items = vec![i1];
        items.extend(i2.into_iter().map(|e| e.1));
        items
    }
};

Constant: ast::Constant = {
    <b:bytes+> => ast::Constant::Bytes(b.into_iter().flatten().collect()),
    <value:int> => ast::Constant::Int(value),
    <value:float> => ast::Constant::Float(value),
    <s:complex> => ast::Constant::Complex { real: s.0, imag: s.1 },
};

Bytes: Vec<u8> = {
    <s:bytes+> => {
        s.into_iter().flatten().collect::<Vec<u8>>()
    },
};

Identifier: String = <s:name> => s;

// Hook external lexer:
extern {
    type Location = ast::Location;
    type Error = LexicalError;

    enum lexer::Tok {
        Indent => lexer::Tok::Indent,
        Dedent => lexer::Tok::Dedent,
        StartModule => lexer::Tok::StartModule,
        StartInteractive => lexer::Tok::StartInteractive,
        StartExpression => lexer::Tok::StartExpression,
        "+" => lexer::Tok::Plus,
        "-" => lexer::Tok::Minus,
        "~" => lexer::Tok::Tilde,
        ":" => lexer::Tok::Colon,
        "." => lexer::Tok::Dot,
        "..." => lexer::Tok::Ellipsis,
        "," => lexer::Tok::Comma,
        "*" => lexer::Tok::Star,
        "**" => lexer::Tok::DoubleStar,
        "&" => lexer::Tok::Amper,
        "@" => lexer::Tok::At,
        "%" => lexer::Tok::Percent,
        "//" => lexer::Tok::DoubleSlash,
        "^" => lexer::Tok::CircumFlex,
        "|" => lexer::Tok::Vbar,
        "<<" => lexer::Tok::LeftShift,
        ">>" => lexer::Tok::RightShift,
        "/" => lexer::Tok::Slash,
        "(" => lexer::Tok::Lpar,
        ")" => lexer::Tok::Rpar,
        "[" => lexer::Tok::Lsqb,
        "]" => lexer::Tok::Rsqb,
        "{" => lexer::Tok::Lbrace,
        "}" => lexer::Tok::Rbrace,
        "=" => lexer::Tok::Equal,
        "+=" => lexer::Tok::PlusEqual,
        "-=" => lexer::Tok::MinusEqual,
        "*=" => lexer::Tok::StarEqual,
        "@=" => lexer::Tok::AtEqual,
        "/=" => lexer::Tok::SlashEqual,
        "%=" => lexer::Tok::PercentEqual,
        "&=" => lexer::Tok::AmperEqual,
        "|=" => lexer::Tok::VbarEqual,
        "^=" => lexer::Tok::CircumflexEqual,
        "<<=" => lexer::Tok::LeftShiftEqual,
        ">>=" => lexer::Tok::RightShiftEqual,
        "**=" => lexer::Tok::DoubleStarEqual,
        "//=" => lexer::Tok::DoubleSlashEqual,
        ":=" => lexer::Tok::ColonEqual,
        "==" => lexer::Tok::EqEqual,
        "!=" => lexer::Tok::NotEqual,
        "<" => lexer::Tok::Less,
        "<=" => lexer::Tok::LessEqual,
        ">" => lexer::Tok::Greater,
        ">=" => lexer::Tok::GreaterEqual,
        "->" => lexer::Tok::Rarrow,
        "and" => lexer::Tok::And,
        "as" => lexer::Tok::As,
        "assert" => lexer::Tok::Assert,
        "async" => lexer::Tok::Async,
        "await" => lexer::Tok::Await,
        "break" => lexer::Tok::Break,
        "class" => lexer::Tok::Class,
        "continue" => lexer::Tok::Continue,
        "def" => lexer::Tok::Def,
        "del" => lexer::Tok::Del,
        "elif" => lexer::Tok::Elif,
        "else" => lexer::Tok::Else,
        "except" => lexer::Tok::Except,
        "finally" => lexer::Tok::Finally,
        "for" => lexer::Tok::For,
        "from" => lexer::Tok::From,
        "global" => lexer::Tok::Global,
        "if" => lexer::Tok::If,
        "in" => lexer::Tok::In,
        "is" => lexer::Tok::Is,
        "import" => lexer::Tok::Import,
        "from" => lexer::Tok::From,
        "lambda" => lexer::Tok::Lambda,
        "nonlocal" => lexer::Tok::Nonlocal,
        "not" => lexer::Tok::Not,
        "or" => lexer::Tok::Or,
        "pass" => lexer::Tok::Pass,
        "raise" => lexer::Tok::Raise,
        "return" => lexer::Tok::Return,
        "try" => lexer::Tok::Try,
        "while" => lexer::Tok::While,
        "with" => lexer::Tok::With,
        "yield" => lexer::Tok::Yield,
        "True" => lexer::Tok::True,
        "False" => lexer::Tok::False,
        "None" => lexer::Tok::None,
        int => lexer::Tok::Int { value: <BigInt> },
        float => lexer::Tok::Float { value: <f64> },
        complex => lexer::Tok::Complex { real: <f64>, imag: <f64> },
        string => lexer::Tok::String { value: <String>, is_fstring: <bool> },
        bytes => lexer::Tok::Bytes { value: <Vec<u8>> },
        name => lexer::Tok::Name { name: <String> },
        "\n" => lexer::Tok::Newline,
        ";" => lexer::Tok::Semi,
    }
}