//! # Proposals discussion module
//! Proposals `discussion` module for the Joystream platform. Version 3.
//! It contains discussion subsystem of the proposals.
//!
//! ## Overview
//!
//! The proposals discussion module is used by the codex module to provide a platform for discussions
//! about different proposals. It allows to create discussion threads and then add and update related
//! posts.
//!
//! ## Supported extrinsics
//! - [add_post](./struct.Module.html#method.add_post) - adds a post to an existing discussion thread
//! - [update_post](./struct.Module.html#method.update_post) - updates existing post
//! - [change_thread_mode](./struct.Module.html#method.change_thread_mode) - changes thread permission mode
//!
//! ## Public API methods
//! - [create_thread](./struct.Module.html#method.create_thread) - creates a discussion thread
//! - [ensure_can_create_thread](./struct.Module.html#method.ensure_can_create_thread) - ensures safe thread creation
//!
//! ## Usage
//!
//! ```
//! use frame_support::decl_module;
//! use frame_system::ensure_root;
//! use pallet_proposals_discussion::{self as discussions, ThreadMode};
//!
//! pub trait Trait: discussions::Trait + membership::Trait {}
//!
//! decl_module! {
//!     pub struct Module<T: Trait> for enum Call where origin: T::Origin {
//!         #[weight = 10_000_000]
//!         pub fn create_discussion(origin, title: Vec<u8>, author_id : T::MemberId) {
//!             ensure_root(origin)?;
//!             let thread_mode = ThreadMode::Open;
//!             <discussions::Module<T>>::ensure_can_create_thread(&thread_mode)?;
//!             <discussions::Module<T>>::create_thread(author_id, thread_mode)?;
//!         }
//!     }
//! }
//! # fn main() {}
//! ```

// Ensure we're `no_std` when compiling for Wasm.
#![cfg_attr(not(feature = "std"), no_std)]

// Do not delete! Cannot be uncommented by default, because of Parity decl_module! issue.
//#![warn(missing_docs)]

mod benchmarking;
#[cfg(test)]
mod tests;
mod types;

use frame_support::dispatch::{DispatchError, DispatchResult};
use frame_support::sp_runtime::SaturatedConversion;
use frame_support::traits::Get;
use frame_support::{
    decl_error, decl_event, decl_module, decl_storage, ensure, weights::Weight, Parameter,
};
use sp_std::clone::Clone;
use sp_std::vec::Vec;

use common::origin::ActorOriginValidator;
use types::{DiscussionPost, DiscussionThread};

pub use types::ThreadMode;

type MemberId<T> = <T as membership::Trait>::MemberId;

/// Proposals discussion WeightInfo.
/// Note: This was auto generated through the benchmark CLI using the `--weight-trait` flag
pub trait WeightInfo {
    fn add_post(i: u32) -> Weight; // Note: since parameter doesn't affect weight it's discarded
    fn update_post() -> Weight; // Note: since parameter doesn't affect weight it's discarded
    fn change_thread_mode(i: u32) -> Weight;
}

type WeightInfoDiscussion<T> = <T as Trait>::WeightInfo;

decl_event!(
    /// Proposals engine events
    pub enum Event<T>
    where
        <T as Trait>::ThreadId,
        MemberId = MemberId<T>,
        <T as Trait>::PostId,
    {
        /// Emits on thread creation.
        ThreadCreated(ThreadId, MemberId),

        /// Emits on post creation.
        PostCreated(PostId, MemberId),

        /// Emits on post update.
        PostUpdated(PostId, MemberId),

        /// Emits on thread mode change.
        ThreadModeChanged(ThreadId, ThreadMode<MemberId>),
    }
);

/// Defines whether the member is an active councilor.
pub trait CouncilMembership<AccountId, MemberId> {
    /// Defines whether the member is an active councilor.
    fn is_council_member(account_id: &AccountId, member_id: &MemberId) -> bool;
}

/// 'Proposal discussion' substrate module Trait
pub trait Trait: frame_system::Trait + membership::Trait {
    /// Discussion event type.
    type Event: From<Event<Self>> + Into<<Self as frame_system::Trait>::Event>;

    /// Validates post author id and origin combination
    type AuthorOriginValidator: ActorOriginValidator<Self::Origin, MemberId<Self>, Self::AccountId>;

    /// Defines whether the member is an active councilor.
    type CouncilOriginValidator: ActorOriginValidator<Self::Origin, MemberId<Self>, Self::AccountId>;

    /// Discussion thread Id type
    type ThreadId: From<u64> + Into<u64> + Parameter + Default + Copy;

    /// Post Id type
    type PostId: From<u64> + Parameter + Default + Copy;

    /// Defines author list size limit for the Closed discussion.
    type MaxWhiteListSize: Get<u32>;

    /// Weight information for extrinsics in this pallet.
    type WeightInfo: WeightInfo;
}

decl_error! {
    /// Discussion module predefined errors
    pub enum Error for Module<T: Trait> {
        /// Author should match the post creator
        NotAuthor,

        /// Thread doesn't exist
        ThreadDoesntExist,

        /// Post doesn't exist
        PostDoesntExist,

        /// Require root origin in extrinsics
        RequireRootOrigin,

        /// The thread has Closed mode. And post author doesn't belong to council or allowed members.
        CannotPostOnClosedThread,

        /// Should be thread author or councilor.
        NotAuthorOrCouncilor,

        /// Max allowed authors list limit exceeded.
        MaxWhiteListSizeExceeded,
    }
}

// Storage for the proposals discussion module
decl_storage! {
    pub trait Store for Module<T: Trait> as ProposalDiscussion {
        /// Map thread identifier to corresponding thread.
        pub ThreadById get(fn thread_by_id): map hasher(blake2_128_concat)
            T::ThreadId => DiscussionThread<MemberId<T>, T::BlockNumber, MemberId<T>>;

        /// Count of all threads that have been created.
        pub ThreadCount get(fn thread_count): u64;

        /// Map thread id and post id to corresponding post.
        pub PostThreadIdByPostId:
            double_map hasher(blake2_128_concat) T::ThreadId, hasher(blake2_128_concat) T::PostId =>
                DiscussionPost<MemberId<T>>;

        /// Count of all posts that have been created.
        pub PostCount get(fn post_count): u64;
    }
}

decl_module! {
    /// 'Proposal discussion' substrate module
    pub struct Module<T: Trait> for enum Call where origin: T::Origin {
        /// Predefined errors
        type Error = Error<T>;

        /// Emits an event. Default substrate implementation.
        fn deposit_event() = default;

        /// Adds a post with author origin check.
        ///
        /// <weight>
        ///
        /// ## Weight
        /// `O (W)` where:
        /// - `W` is the number of whitelisted members for `thread_id`
        /// - DB:
        ///    - O(1) doesn't depend on the state or parameters
        /// # </weight>
        #[weight = WeightInfoDiscussion::<T>::add_post(
            T::MaxWhiteListSize::get(),
        )]
        pub fn add_post(
            origin,
            post_author_id: MemberId<T>,
            thread_id : T::ThreadId,
            _text : Vec<u8>
        ) {
            T::AuthorOriginValidator::ensure_actor_origin(
                origin.clone(),
                post_author_id,
            )?;

            ensure!(<ThreadById<T>>::contains_key(thread_id), Error::<T>::ThreadDoesntExist);

            Self::ensure_thread_mode(origin, post_author_id, thread_id)?;

            // mutation

            let next_post_count_value = Self::post_count() + 1;
            let new_post_id = next_post_count_value;

            let new_post = DiscussionPost {
                author_id: post_author_id,
            };

            let post_id = T::PostId::from(new_post_id);
            <PostThreadIdByPostId<T>>::insert(thread_id, post_id, new_post);
            PostCount::put(next_post_count_value);
            Self::deposit_event(RawEvent::PostCreated(post_id, post_author_id));
       }

        /// Updates a post with author origin check. Update attempts number is limited.
        ///
        /// <weight>
        ///
        /// ## Weight
        /// `O (1)` doesn't depend on the state or parameters
        /// - DB:
        ///    - O(1) doesn't depend on the state or parameters
        /// # </weight>
        #[weight = WeightInfoDiscussion::<T>::update_post()]
        pub fn update_post(
            origin,
            post_author_id: MemberId<T>,
            thread_id: T::ThreadId,
            post_id : T::PostId,
            _text : Vec<u8>
        ){
            T::AuthorOriginValidator::ensure_actor_origin(
                origin,
                post_author_id,
            )?;

            ensure!(<ThreadById<T>>::contains_key(thread_id), Error::<T>::ThreadDoesntExist);
            ensure!(<PostThreadIdByPostId<T>>::contains_key(thread_id, post_id), Error::<T>::PostDoesntExist);

            let post = <PostThreadIdByPostId<T>>::get(&thread_id, &post_id);

            ensure!(post.author_id == post_author_id, Error::<T>::NotAuthor);

            // mutation

            Self::deposit_event(RawEvent::PostUpdated(post_id, post_author_id));
       }

        /// Changes thread permission mode.
        ///
        /// <weight>
        ///
        /// ## Weight
        /// `O (W)` if ThreadMode is close or O(1) otherwise where:
        /// - `W` is the number of whitelisted members in `mode`
        /// - DB:
        ///    - O(1) doesn't depend on the state or parameters
        /// # </weight>
        #[weight = WeightInfoDiscussion::<T>::change_thread_mode(
            if let ThreadMode::Closed(ref list) = mode {
                list.len().saturated_into()
            } else {
                0
            }
        )]
        pub fn change_thread_mode(
            origin,
            member_id: MemberId<T>,
            thread_id : T::ThreadId,
            mode : ThreadMode<MemberId<T>>
        ) {
            T::AuthorOriginValidator::ensure_actor_origin(origin.clone(), member_id)?;

            ensure!(<ThreadById<T>>::contains_key(thread_id), Error::<T>::ThreadDoesntExist);

            if let ThreadMode::Closed(ref list) = mode{
                ensure!(
                    list.len() <= (T::MaxWhiteListSize::get()).saturated_into(),
                    Error::<T>::MaxWhiteListSizeExceeded
                );
            }

            let thread = Self::thread_by_id(&thread_id);

            let is_councilor =
                    T::CouncilOriginValidator::ensure_actor_origin(origin, member_id)
                        .is_ok();
            let is_thread_author = thread.author_id == member_id;

            ensure!(is_thread_author || is_councilor, Error::<T>::NotAuthorOrCouncilor);

            // mutation

            <ThreadById<T>>::mutate(thread_id, |thread| {
                thread.mode = mode.clone();
            });

            Self::deposit_event(RawEvent::ThreadModeChanged(thread_id, mode));
       }
    }
}

impl<T: Trait> Module<T> {
    /// Create the discussion thread.
    /// times in a row by the same author.
    pub fn create_thread(
        thread_author_id: MemberId<T>,
        mode: ThreadMode<MemberId<T>>,
    ) -> Result<T::ThreadId, DispatchError> {
        Self::ensure_can_create_thread(&mode)?;

        let next_thread_count_value = Self::thread_count() + 1;
        let new_thread_id = next_thread_count_value;

        let new_thread = DiscussionThread {
            activated_at: Self::current_block(),
            author_id: thread_author_id,
            mode,
        };

        // mutation

        let thread_id = T::ThreadId::from(new_thread_id);
        <ThreadById<T>>::insert(thread_id, new_thread);
        ThreadCount::put(next_thread_count_value);
        Self::deposit_event(RawEvent::ThreadCreated(thread_id, thread_author_id));

        Ok(thread_id)
    }

    /// Ensures thread can be created.
    /// Checks:
    /// - max allowed authors for the Closed thread mode
    pub fn ensure_can_create_thread(mode: &ThreadMode<MemberId<T>>) -> DispatchResult {
        if let ThreadMode::Closed(list) = mode {
            ensure!(
                list.len() <= (T::MaxWhiteListSize::get()).saturated_into(),
                Error::<T>::MaxWhiteListSizeExceeded
            );
        }

        Ok(())
    }
}

impl<T: Trait> Module<T> {
    // Wrapper-function over System::block_number()
    fn current_block() -> T::BlockNumber {
        <frame_system::Module<T>>::block_number()
    }

    fn ensure_thread_mode(
        origin: T::Origin,
        thread_author_id: MemberId<T>,
        thread_id: T::ThreadId,
    ) -> DispatchResult {
        let thread = Self::thread_by_id(thread_id);

        match thread.mode {
            ThreadMode::Open => Ok(()),
            ThreadMode::Closed(members) => {
                let is_thread_author = thread_author_id == thread.author_id;
                let is_councilor =
                    T::CouncilOriginValidator::ensure_actor_origin(origin, thread_author_id)
                        .is_ok();
                let is_allowed_member = members
                    .iter()
                    .any(|member_id| *member_id == thread_author_id);

                if is_thread_author || is_councilor || is_allowed_member {
                    Ok(())
                } else {
                    Err(Error::<T>::CannotPostOnClosedThread.into())
                }
            }
        }
    }
}