/// obtain class and function signature from AST
use super::context::TopLevelContext;
use super::primitives::*;
use super::typedef::*;
use rustpython_parser::ast::{ExpressionType, Statement, StatementType, StringGroup};
use std::collections::HashMap;

fn typename_from_expr<'b: 'a, 'a>(typenames: &mut Vec<&'a str>, expr: &'b ExpressionType) {
    match expr {
        ExpressionType::Identifier { name } => typenames.push(&name),
        ExpressionType::String { value } => match value {
            StringGroup::Constant { value } => typenames.push(&value),
            _ => unimplemented!(),
        },
        ExpressionType::Subscript { a, b } => {
            typename_from_expr(typenames, &b.node);
            typename_from_expr(typenames, &a.node)
        }
        _ => unimplemented!(),
    }
}

fn typename_from_fn<'b: 'a, 'a>(typenames: &mut Vec<&'a str>, fun: &'b StatementType) {
    match fun {
        StatementType::FunctionDef { args, returns, .. } => {
            for arg in args.args.iter() {
                if let Some(ann) = &arg.annotation {
                    typename_from_expr(typenames, &ann.node);
                }
            }
            if let Some(returns) = &returns {
                typename_from_expr(typenames, &returns.node);
            }
        }
        _ => unreachable!(),
    }
}

fn name_from_expr<'b: 'a, 'a>(expr: &'b ExpressionType) -> &'a str {
    match &expr {
        ExpressionType::Identifier { name } => &name,
        ExpressionType::String { value } => match value {
            StringGroup::Constant { value } => &value,
            _ => unimplemented!(),
        },
        _ => unimplemented!(),
    }
}

fn type_from_expr<'b: 'a, 'a>(
    ctx: &'a TopLevelContext,
    expr: &'b ExpressionType,
) -> Result<Type, String> {
    match expr {
        ExpressionType::Identifier { name } => {
            ctx.get_type(name).ok_or_else(|| "no such type".into())
        }
        ExpressionType::String { value } => match value {
            StringGroup::Constant { value } => {
                ctx.get_type(&value).ok_or_else(|| "no such type".into())
            }
            _ => unimplemented!(),
        },
        ExpressionType::Subscript { a, b } => {
            if let ExpressionType::Identifier { name } = &a.node {
                match name.as_str() {
                    "list" => {
                        let ty = type_from_expr(ctx, &b.node)?;
                        Ok(TypeEnum::ParametricType(LIST_TYPE, vec![ty]).into())
                    }
                    "tuple" => {
                        if let ExpressionType::Tuple { elements } = &b.node {
                            let ty_list: Result<Vec<_>, _> = elements
                                .iter()
                                .map(|v| type_from_expr(ctx, &v.node))
                                .collect();
                            Ok(TypeEnum::ParametricType(TUPLE_TYPE, ty_list?).into())
                        } else {
                            Err("unsupported format".into())
                        }
                    }
                    _ => Err("no such parameterized type".into()),
                }
            } else {
                // we require a to be an identifier, for a[b]
                Err("unsupported format".into())
            }
        }
        _ => Err("unsupported format".into()),
    }
}

pub fn get_typenames<'b: 'a, 'a>(stmts: &'b [Statement]) -> (Vec<&'a str>, Vec<&'a str>) {
    let mut classes = Vec::new();
    let mut typenames = Vec::new();
    for stmt in stmts.iter() {
        match &stmt.node {
            StatementType::ClassDef {
                name, body, bases, ..
            } => {
                // check if class is not duplicated...
                // and annotations
                classes.push(&name[..]);
                for base in bases.iter() {
                    let name = name_from_expr(&base.node);
                    typenames.push(name);
                }
                // may check if fields/functions are not duplicated
                for stmt in body.iter() {
                    match &stmt.node {
                        StatementType::AnnAssign { annotation, .. } => {
                            typename_from_expr(&mut typenames, &annotation.node)
                        }
                        StatementType::FunctionDef { .. } => {
                            typename_from_fn(&mut typenames, &stmt.node);
                        }
                        _ => unimplemented!(),
                    }
                }
            }
            StatementType::FunctionDef { .. } => {
                // may check annotations
                typename_from_fn(&mut typenames, &stmt.node);
            }
            _ => (),
        }
    }
    let mut unknowns = Vec::new();
    for n in typenames {
        if !PRIMITIVES.contains(&n) && !classes.contains(&n) && !unknowns.contains(&n) {
            unknowns.push(n);
        }
    }
    (classes, unknowns)
}

fn resolve_function<'b: 'a, 'a>(
    ctx: &'a TopLevelContext,
    fun: &'b StatementType,
) -> Result<FnDef, String> {
    if let StatementType::FunctionDef { args, returns, .. } = &fun {
        let args: Result<Vec<_>, _> = args
            .args
            .iter()
            .map(|arg| type_from_expr(ctx, &arg.annotation.as_ref().unwrap().node))
            .collect();
        let args = args?;
        let result = match returns {
            Some(v) => Some(type_from_expr(ctx, &v.node)?),
            None => None,
        };
        Ok(FnDef { args, result })
    } else {
        unreachable!()
    }
}

pub fn resolve_signatures<'b: 'a, 'a>(ctx: &'a mut TopLevelContext<'a>, stmts: &'b [Statement]) {
    for stmt in stmts.iter() {
        match &stmt.node {
            StatementType::ClassDef {
                name, bases, body, ..
            } => {
                let mut parents = Vec::new();
                for base in bases.iter() {
                    let name = name_from_expr(&base.node);
                    let c = ctx.get_type(name).unwrap();
                    let id = if let TypeEnum::ClassType(id) = c.as_ref() {
                        *id
                    } else {
                        unreachable!()
                    };
                    parents.push(id);
                }

                let mut fields = HashMap::new();
                let mut functions = HashMap::new();

                for stmt in body.iter() {
                    match &stmt.node {
                        StatementType::AnnAssign {
                            target, annotation, ..
                        } => {
                            let name = name_from_expr(&target.node);
                            let ty = type_from_expr(ctx, &annotation.node).unwrap();
                            fields.insert(name, ty);
                        }
                        StatementType::FunctionDef { name, .. } => {
                            functions.insert(&name[..], resolve_function(ctx, &stmt.node).unwrap());
                        }
                        _ => unimplemented!(),
                    }
                }

                let class = ctx.get_type(name).unwrap();
                let class = if let TypeEnum::ClassType(id) = class.as_ref() {
                    ctx.get_class_def_mut(*id)
                } else {
                    unreachable!()
                };
                class.parents.extend_from_slice(&parents);
                class.base.fields.clone_from(&fields);
                class.base.methods.clone_from(&functions);
            }
            StatementType::FunctionDef { name, .. } => {
                ctx.add_fn(&name[..], resolve_function(ctx, &stmt.node).unwrap());
            }
            _ => unimplemented!(),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use indoc::indoc;
    use rustpython_parser::parser::parse_program;

    #[test]
    fn test_get_classes() {
        let ast = parse_program(indoc! {"
            class Foo:
                a: int32
                b: Test

                def test(self, a: int32) -> Test2:
                    return b

            class Bar(Foo, 'FooBar'):
                def test2(self, a: list[Foo]) -> Test2:
                    return b

                def test3(self, a: list[FooBar2]) -> Test2:
                    return b
        " })
        .unwrap();
        let (mut classes, mut unknowns) = get_typenames(&ast.statements);
        let classes_count = classes.len();
        let unknowns_count = unknowns.len();
        classes.sort();
        unknowns.sort();
        assert_eq!(classes.len(), classes_count);
        assert_eq!(unknowns.len(), unknowns_count);
        assert_eq!(&classes, &["Bar", "Foo"]);
        assert_eq!(&unknowns, &["FooBar", "FooBar2", "Test", "Test2"]);
    }
}