use crate::errors::Error;
use crate::models::proto::cofd::*;
use crate::models::users::User;
use prost::bytes::BytesMut;
use serde::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
        }
    }
}

/// Enum representing all game systems supported by the character
/// service. Game systems are kept unique instead of lumping them
/// together under common umbrella systems, even if the different
/// games use the same (or similar) character sheets. This is because
/// of the possibility for slight differences in rules and data
/// between even similar systems. It's simpler to err on the side of
/// uniqueness. Usually, systems based on the same ruleset will have
/// one character sheet type, with a oneof field for game-specific
/// information.
#[derive(Debug, Serialize, PartialEq, Clone, Copy, EnumIter, EnumString, sqlx::Type)]
#[sqlx(rename_all = "snake_case")]
pub enum CharacterDataType {
    /// A character for the core Chronicles of Darkness rules.
    ChroniclesOfDarkness,

    /// A character for Changeling 2E rules.
    Changeling,
}

impl CharacterDataType {
    /// Create the default serialized protobuf data (character sheet)
    /// for the game system represented by the enum variant.
    pub fn default_serialized_data(&self) -> Result<BytesMut, Error> {
        use prost::Message;
        use CharacterDataType::*;
        let data: BytesMut = match self {
            ChroniclesOfDarkness | Changeling => {
                let sheet = CofdSheet::default_sheet(*self);
                let mut buf = BytesMut::with_capacity(std::mem::size_of_val(&sheet));
                sheet.encode(&mut buf)?;
                buf
            }
        };

        Ok(data)
    }

    /// Returns whether or not this enum variant represents a Chronicles
    /// of Darkness game system.
    pub fn is_cofd_system(&self) -> bool {
        use CharacterDataType::*;
        match self {
            ChroniclesOfDarkness | Changeling => true,
        }
    }
}

/// An entry that appears in a user's character list. Properties are
/// in order of table columns.
#[derive(Serialize, Debug, sqlx::FromRow)]
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 {
            ChroniclesOfDarkness => Box::new(self.try_deserialize::<CofdSheet>()?),
            Changeling => Box::new(self.try_deserialize::<CofdSheet>()?),
        };

        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)
    }

    /// Update the existing character with new serialized protobuf
    /// data.
    pub fn update_data<T>(&mut self, data: &T) -> Result<(), Error>
    where
        T: prost::Message + std::default::Default,
    {
        let mut buf = BytesMut::with_capacity(std::mem::size_of_val(&data));
        data.encode(&mut buf)?;
        self.data = buf.to_vec();
        Ok(())
    }
}

/// Same as regular character type, but without the actual protobuf
/// data loaded into memory.
#[derive(Serialize, Debug, sqlx::FromRow)]
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.
pub struct NewCharacter<'a> {
    pub user_id: i32,
    pub viewable: bool,
    pub character_name: &'a str,
    pub data_type: CharacterDataType,
    pub data_version: i32,
    pub data: &'a [u8],
}