use crate::errors::Error;
use crate::models::proto::cofd::*;
use crate::models::users::User;
use crate::schema::characters;
use diesel_derive_enum::DbEnum;
use prost::bytes::BytesMut;
use serde_derive::Serialize;
use strum::{EnumIter, EnumString};

/// Dynamic character data is an opaque container type that holds
/// successfully deserialized character data protobuf object of any
/// type. It does not know what kind of type it has. This is a
/// semantically more appropriate name for what is returned from the
/// dyn_deserialize function.
pub(crate) type DynCharacterData = dyn erased_serde::Serialize;

/// Control system visibility of a character for a particular user.
/// Implemented as a trait because there are multiple character
/// structs that need this.
pub(crate) trait Visibility {
    /// User ID that owns this character.
    fn user_id(&self) -> i32;

    /// If the character is publicly visible.
    fn viewable(&self) -> bool;

    /// Transform to an Option that holds the character, if the
    /// character is viewable to a potentially existing user. A
    /// character is "visible" if the public viewable property is set
    /// to true, or the user is the owner of the character. Consumes
    /// self.
    fn as_visible_for(self, user: Option<&User>) -> Option<Self>
    where
        Self: std::marker::Sized,
    {
        if self.viewable() || user.map(|u| u.id) == Some(self.user_id()) {
            Some(self)
        } else {
            None
        }
    }
}

#[derive(DbEnum, Debug, Serialize, PartialEq, Clone, Copy, EnumIter, EnumString)]
pub enum CharacterDataType {
    ChroniclesOfDarknessV1,
    ChangelingV1,
}

impl CharacterDataType {
    pub fn create_data(&self) -> Result<BytesMut, Error> {
        use prost::Message;
        use CharacterDataType::*;
        let data: BytesMut = match self {
            ChroniclesOfDarknessV1 => {
                let sheet = CofdSheet::default();
                let mut buf = BytesMut::with_capacity(std::mem::size_of_val(&sheet));
                sheet.encode(&mut buf)?;
                buf
            }
            ChangelingV1 => {
                let mut sheet = ChangelingSheet::default();
                sheet.base = Some(CofdSheet::default());
                let mut buf = BytesMut::with_capacity(std::mem::size_of_val(&sheet));
                sheet.encode(&mut buf)?;
                buf
            }
        };

        Ok(data)
    }
}

/// An entry that appears in a user's character list. Properties are
/// in order of table columns.
#[derive(Serialize, Debug, Queryable)]
pub struct Character {
    pub id: i32,
    pub user_id: i32,
    pub viewable: bool,
    pub character_name: String,
    pub data_type: CharacterDataType,
    pub data_version: i32,
    pub data: Vec<u8>,
}

impl Visibility for Character {
    fn user_id(&self) -> i32 {
        self.user_id
    }

    fn viewable(&self) -> bool {
        self.viewable
    }
}

impl Character {
    /// Attempt to deserialize the character's data into the given
    /// type, which must be one of the protobuf types.
    pub fn try_deserialize<T>(&self) -> Result<T, Error>
    where
        T: prost::Message + std::default::Default,
    {
        let decoded = T::decode(self.data.as_ref())?;
        Ok(decoded)
    }

    /// Attempt to deserialize the character's data based on its
    /// stored type, but return the deserialized protobuf type as a
    /// trait object. Primarily used for passing character sheets to
    /// templates or other places (like a REST API).
    pub fn dyn_deserialize(&self) -> Result<Box<DynCharacterData>, Error> {
        use CharacterDataType::*;
        let decoded: Box<dyn erased_serde::Serialize> = match self.data_type {
            ChroniclesOfDarknessV1 => Box::new(self.try_deserialize::<CofdSheet>()?),
            ChangelingV1 => Box::new(self.try_deserialize::<ChangelingSheet>()?),
        };

        Ok(decoded)
    }

    /// Upgrade the stored protobuf character data to its newest
    /// iteration, if new types have been created. Consumes self.
    pub fn uprade(self) -> Result<Character, Error> {
        // Currently, this just returns itself because there are no
        // iterations. But we could for example go from CofdSheet v1
        // to CofdSheet v2 by deserializing v1, applying a migration
        // to v2, then reserializing, and copying over all other
        // fields.
        Ok(self)
    }
}

#[derive(Serialize, Debug, Queryable)]
pub struct StrippedCharacter {
    pub id: i32,
    pub user_id: i32,
    pub viewable: bool,
    pub character_name: String,
    pub data_type: CharacterDataType,
    pub data_version: i32,
}

impl Visibility for StrippedCharacter {
    fn user_id(&self) -> i32 {
        self.user_id
    }

    fn viewable(&self) -> bool {
        self.viewable
    }
}

/// Represents insert of a new character into the database. Property
/// names correspond to columns.
#[derive(Insertable)]
#[table_name = "characters"]
pub struct NewCharacter {
    pub user_id: i32,
    pub viewable: bool,
    pub character_name: String,
    pub data_type: CharacterDataType,
    pub data_version: i32,
    pub data: Vec<u8>,
}