use std::collections::HashMap;
use std::marker;

use crate::descriptor::DescriptorProto;
use crate::descriptor::FileDescriptorProto;
use crate::descriptorx::find_message_by_rust_name;
use crate::reflect::acc::FieldAccessor;
use crate::reflect::find_message_or_enum::find_message_or_enum;
use crate::reflect::find_message_or_enum::MessageOrEnum;
use crate::reflect::FieldDescriptor;
use crate::Message;

trait MessageFactory: Send + Sync + 'static {
    fn new_instance(&self) -> Box<dyn Message>;
}

struct MessageFactoryImpl<M>(marker::PhantomData<M>);

impl<M> MessageFactory for MessageFactoryImpl<M>
where
    M: 'static + Message + Default + Clone + PartialEq,
{
    fn new_instance(&self) -> Box<dyn Message> {
        let m: M = Default::default();
        Box::new(m)
    }
}

/// Dynamic message type
pub struct MessageDescriptor {
    full_name: String,
    proto: &'static DescriptorProto,
    factory: &'static dyn MessageFactory,
    fields: Vec<FieldDescriptor>,

    index_by_name: HashMap<String, usize>,
    index_by_name_or_json_name: HashMap<String, usize>,
    index_by_number: HashMap<u32, usize>,
}

impl MessageDescriptor {
    /// Get underlying `DescriptorProto` object.
    pub fn get_proto(&self) -> &DescriptorProto {
        self.proto
    }

    /// Get a message descriptor for given message type
    pub fn for_type<M: Message>() -> &'static MessageDescriptor {
        M::descriptor_static()
    }

    fn compute_full_name(package: &str, path_to_package: &str, proto: &DescriptorProto) -> String {
        let mut full_name = package.to_owned();
        if path_to_package.len() != 0 {
            if full_name.len() != 0 {
                full_name.push('.');
            }
            full_name.push_str(path_to_package);
        }
        if full_name.len() != 0 {
            full_name.push('.');
        }
        full_name.push_str(proto.get_name());
        full_name
    }

    // Non-generic part of `new` is a separate function
    // to reduce code bloat from multiple instantiations.
    fn new_non_generic_by_rust_name(
        rust_name: &'static str,
        fields: Vec<FieldAccessor>,
        file: &'static FileDescriptorProto,
        factory: &'static dyn MessageFactory,
    ) -> MessageDescriptor {
        let proto = find_message_by_rust_name(file, rust_name);

        let mut field_proto_by_name = HashMap::new();
        for field_proto in proto.message.get_field() {
            field_proto_by_name.insert(field_proto.get_name(), field_proto);
        }

        let mut index_by_name = HashMap::new();
        let mut index_by_name_or_json_name = HashMap::new();
        let mut index_by_number = HashMap::new();

        let mut full_name = file.get_package().to_string();
        if full_name.len() > 0 {
            full_name.push('.');
        }
        full_name.push_str(proto.message.get_name());

        let fields: Vec<_> = fields
            .into_iter()
            .map(|f| {
                let proto = *field_proto_by_name.get(&f.name).unwrap();
                FieldDescriptor::new(f, proto)
            })
            .collect();
        for (i, f) in fields.iter().enumerate() {
            assert!(index_by_number
                .insert(f.proto().get_number() as u32, i)
                .is_none());
            assert!(index_by_name
                .insert(f.proto().get_name().to_owned(), i)
                .is_none());
            assert!(index_by_name_or_json_name
                .insert(f.proto().get_name().to_owned(), i)
                .is_none());

            let json_name = f.json_name().to_owned();

            if json_name != f.proto().get_name() {
                assert!(index_by_name_or_json_name.insert(json_name, i).is_none());
            }
        }
        MessageDescriptor {
            full_name,
            proto: proto.message,
            factory,
            fields,
            index_by_name,
            index_by_name_or_json_name,
            index_by_number,
        }
    }

    // Non-generic part of `new` is a separate function
    // to reduce code bloat from multiple instantiations.
    fn new_non_generic_by_pb_name(
        protobuf_name_to_package: &'static str,
        fields: Vec<FieldAccessor>,
        file_descriptor_proto: &'static FileDescriptorProto,
        factory: &'static dyn MessageFactory,
    ) -> MessageDescriptor {
        let (path_to_package, proto) =
            match find_message_or_enum(file_descriptor_proto, protobuf_name_to_package) {
                (path_to_package, MessageOrEnum::Message(m)) => (path_to_package, m),
                (_, MessageOrEnum::Enum(_)) => panic!("not a message"),
            };

        let mut field_proto_by_name = HashMap::new();
        for field_proto in proto.get_field() {
            field_proto_by_name.insert(field_proto.get_name(), field_proto);
        }

        let mut index_by_name = HashMap::new();
        let mut index_by_name_or_json_name = HashMap::new();
        let mut index_by_number = HashMap::new();

        let full_name = MessageDescriptor::compute_full_name(
            file_descriptor_proto.get_package(),
            &path_to_package,
            &proto,
        );
        let fields: Vec<_> = fields
            .into_iter()
            .map(|f| {
                let proto = *field_proto_by_name.get(&f.name).unwrap();
                FieldDescriptor::new(f, proto)
            })
            .collect();

        for (i, f) in fields.iter().enumerate() {
            assert!(index_by_number
                .insert(f.proto().get_number() as u32, i)
                .is_none());
            assert!(index_by_name
                .insert(f.proto().get_name().to_owned(), i)
                .is_none());
            assert!(index_by_name_or_json_name
                .insert(f.proto().get_name().to_owned(), i)
                .is_none());

            let json_name = f.json_name().to_owned();

            if json_name != f.proto().get_name() {
                assert!(index_by_name_or_json_name.insert(json_name, i).is_none());
            }
        }
        MessageDescriptor {
            full_name,
            proto,
            factory,
            fields,
            index_by_name,
            index_by_name_or_json_name,
            index_by_number,
        }
    }

    /// Construct a new message descriptor.
    ///
    /// This operation is called from generated code and rarely
    /// need to be called directly.
    #[doc(hidden)]
    #[deprecated(
        since = "2.12",
        note = "Please regenerate .rs files from .proto files to use newer APIs"
    )]
    pub fn new<M: 'static + Message + Default + Clone + PartialEq>(
        rust_name: &'static str,
        fields: Vec<FieldAccessor>,
        file: &'static FileDescriptorProto,
    ) -> MessageDescriptor {
        let factory = &MessageFactoryImpl(marker::PhantomData::<M>);
        MessageDescriptor::new_non_generic_by_rust_name(rust_name, fields, file, factory)
    }

    /// Construct a new message descriptor.
    ///
    /// This operation is called from generated code and rarely
    /// need to be called directly.
    #[doc(hidden)]
    pub fn new_pb_name<M: 'static + Message + Default + Clone + PartialEq>(
        protobuf_name_to_package: &'static str,
        fields: Vec<FieldAccessor>,
        file_descriptor_proto: &'static FileDescriptorProto,
    ) -> MessageDescriptor {
        let factory = &MessageFactoryImpl(marker::PhantomData::<M>);
        MessageDescriptor::new_non_generic_by_pb_name(
            protobuf_name_to_package,
            fields,
            file_descriptor_proto,
            factory,
        )
    }

    /// New empty message
    pub fn new_instance(&self) -> Box<dyn Message> {
        self.factory.new_instance()
    }

    /// Message name as given in `.proto` file
    pub fn name(&self) -> &'static str {
        self.proto.get_name()
    }

    /// Fully qualified protobuf message name
    pub fn full_name(&self) -> &str {
        &self.full_name[..]
    }

    /// Message field descriptors.
    pub fn fields(&self) -> &[FieldDescriptor] {
        &self.fields
    }

    /// Find message field by protobuf field name
    ///
    /// Note: protobuf field name might be different for Rust field name.
    pub fn get_field_by_name<'a>(&'a self, name: &str) -> Option<&'a FieldDescriptor> {
        let &index = self.index_by_name.get(name)?;
        Some(&self.fields[index])
    }

    /// Find message field by field name or field JSON name
    pub fn get_field_by_name_or_json_name<'a>(&'a self, name: &str) -> Option<&'a FieldDescriptor> {
        let &index = self.index_by_name_or_json_name.get(name)?;
        Some(&self.fields[index])
    }

    /// Find message field by field name
    pub fn get_field_by_number(&self, number: u32) -> Option<&FieldDescriptor> {
        let &index = self.index_by_number.get(&number)?;
        Some(&self.fields[index])
    }

    /// Find field by name
    // TODO: deprecate
    pub fn field_by_name<'a>(&'a self, name: &str) -> &'a FieldDescriptor {
        // TODO: clone is weird
        let &index = self.index_by_name.get(&name.to_string()).unwrap();
        &self.fields[index]
    }

    /// Find field by number
    // TODO: deprecate
    pub fn field_by_number<'a>(&'a self, number: u32) -> &'a FieldDescriptor {
        let &index = self.index_by_number.get(&number).unwrap();
        &self.fields[index]
    }
}