use super::{
    get_player_item_or_fail, search_item_for_user, user_error, CommandHandlingError, DResult,
    UResult, UserError, UserVerb, UserVerbRef, VerbContext,
};
#[double]
use crate::db::DBTrans;
use crate::{
    db::ItemSearchParams,
    models::item::{FollowData, FollowState, Item},
    regular_tasks::queued_command::{queue_command_for_npc, MovementSource, QueueCommand},
    static_content::room::Direction,
};
use async_trait::async_trait;
use mockall_double::double;
use std::mem;

pub async fn propagate_move_to_followers(
    trans: &DBTrans,
    mover: &Item,
    direction: &Direction,
    source: &MovementSource,
) -> DResult<()> {
    let (event_id, chain) = match source {
        MovementSource::Command { event_id } => (event_id, vec![]),
        MovementSource::Follow { chain, origin_uuid } => (origin_uuid, chain.clone()),
        MovementSource::Internal { .. } => return Ok(()), // Not to be propagated.
    };

    let mut new_chain = chain.clone();
    new_chain.push(mover.refstr());
    let new_movement = QueueCommand::Movement {
        direction: direction.clone(),
        source: MovementSource::Follow {
            origin_uuid: event_id.clone(),
            chain: new_chain,
        },
    };
    for follower in trans.find_followers_by_leader(&mover.refstr()).await? {
        let mut follower_mut = (*follower).clone();
        if !chain.contains(&follower.refstr()) {
            if let Some(&FollowData {
                state: FollowState::IfSameRoom,
                ref follow_whom,
            }) = follower.following.as_ref()
            {
                if follower.location != mover.location {
                    continue;
                }
                follower_mut.following = Some(FollowData {
                    state: FollowState::Active,
                    follow_whom: follow_whom.clone(),
                });
            }
            // We use the NPC variant since adding [queued] will be confusing.
            match queue_command_for_npc(&trans, &mut follower_mut, &new_movement).await {
                Err(e) if e.to_string().starts_with("Can't queue more") => {
                    suspend_follow_for_independent_move(&mut follower_mut);
                }
                Err(e) => return Err(e),
                _ => {}
            }
            trans.save_item_model(&follower_mut).await?;
        }
    }
    Ok(())
}

pub async fn update_follow_for_failed_movement(
    trans: &DBTrans,
    player: &mut Item,
    source: &MovementSource,
) -> DResult<()> {
    // Failing is the same as an independent movement back.
    suspend_follow_for_independent_move(player);

    let event_id = source.event_id();
    for follower in trans.find_followers_by_leader(&player.refstr()).await? {
        if let Some(QueueCommand::Movement {
            source: MovementSource::Follow { origin_uuid, chain },
            ..
        }) = follower.queue.front().as_ref()
        {
            if origin_uuid == event_id && chain.last() == Some(&player.refstr()) {
                // The follower has already started moving (and their followers may indeed have
                // followed them in turn). So we treat the move the follower made
                // but the leader failed as an independent move.
                let mut follower_mut = (*follower).clone();
                suspend_follow_for_independent_move(&mut follower_mut);
                trans.save_item_model(&follower_mut).await?;
                continue;
            }
        }

        // Otherwise, it's not too late, so just cancel it from the queue.
        let mut follower_mut = (*follower).clone();
        follower_mut.queue.retain(|qit| match qit {
            QueueCommand::Movement {
                source: MovementSource::Follow { origin_uuid, chain },
                ..
            } => !(origin_uuid == event_id && chain.last() == Some(&player.refstr())),
            _ => true,
        });
        if follower_mut.queue != follower.queue {
            trans.save_item_model(&follower_mut).await?;
        }
    }
    Ok(())
}

pub fn suspend_follow_for_independent_move(player: &mut Item) {
    if let Some(following) = player.following.as_mut() {
        following.state = FollowState::IfSameRoom;
    }
}

// Caller has to save follower.
pub async fn stop_following(trans: &DBTrans, follower: &mut Item) -> UResult<()> {
    let old_following = mem::replace(&mut follower.following, None)
        .ok_or_else(|| UserError("You're not following anyone.".to_owned()))?;
    if let Some((follow_type, follow_code)) = old_following.follow_whom.split_once("/") {
        if let Some(old_item) = trans
            .find_item_by_type_code(&follow_type, &follow_code)
            .await?
        {
            if follower.item_type == "player" {
                if let Some((session, _session_dat)) =
                    trans.find_session_for_player(&follower.item_code).await?
                {
                    trans
                        .queue_for_session(
                            &session,
                            Some(&format!(
                                "You are no longer following {}.\n",
                                old_item.display_for_sentence(1, false)
                            )),
                        )
                        .await?;
                }
            }
        }
    }
    Ok(())
}

pub async fn cancel_follow_by_leader(trans: &DBTrans, leader: &str) -> DResult<()> {
    for follower in trans.find_followers_by_leader(leader).await? {
        if let Some(player_item) = trans
            .find_item_by_type_code(&follower.item_type, &follower.item_code)
            .await?
        {
            let mut player_item_mut = (*player_item).clone();
            match stop_following(trans, &mut player_item_mut).await {
                Ok(_) => {}
                Err(CommandHandlingError::UserError(_)) => {}
                Err(CommandHandlingError::SystemError(e)) => Err(e)?,
            }
            trans.save_item_model(&player_item_mut).await?;
        }
    }
    Ok(())
}

pub struct Verb;
#[async_trait]
impl UserVerb for Verb {
    async fn handle(
        self: &Self,
        ctx: &mut VerbContext,
        verb: &str,
        remaining: &str,
    ) -> UResult<()> {
        let mut player_item = (*(get_player_item_or_fail(ctx).await?)).clone();
        if verb == "follow" {
            let follow_whom = search_item_for_user(
                ctx,
                &ItemSearchParams {
                    include_loc_contents: true,
                    ..ItemSearchParams::base(&player_item, remaining.trim())
                },
            )
            .await?;
            if follow_whom.item_type != "player" && follow_whom.item_type != "npc" {
                user_error("Only characters (player / NPC) can be followed.".to_owned())?;
            }
            if follow_whom.item_type == "player" && follow_whom.item_code == player_item.item_code {
                user_error("No point chasing your own tail!".to_owned())?;
            }
            if let Some(follow) = player_item.following.as_ref() {
                if follow.follow_whom == follow_whom.refstr() {
                    user_error(format!(
                        "You're already following {}!",
                        follow_whom.pronouns.possessive
                    ))?;
                }
            }
            if ctx
                .trans
                .count_followers_by_leader(&follow_whom.refstr())
                .await?
                >= 20
            {
                user_error(format!(
                    "There's such a huge crowd following {}, there's not really room for more.",
                    &follow_whom.pronouns.object
                ))?;
            }
            if player_item.active_climb.is_some() {
                user_error(
                    "You can't focus on following someone while you are climbing!".to_owned(),
                )?;
            }
            player_item.queue.retain(|qit| match qit {
                QueueCommand::Movement { .. } => false,
                _ => true,
            });
            if let Some(QueueCommand::Movement { direction, source }) =
                follow_whom.queue.front().as_ref()
            {
                let event_id = source.event_id();

                // Safer to make a singleton chain, since follow is manual
                // intervention. Even if the current movement came from player,
                // still want to duplicate it, and don't want to duplicate
                // player in chain.
                let new_chain = vec![follow_whom.refstr()];
                let new_movement = QueueCommand::Movement {
                    direction: direction.clone(),
                    source: MovementSource::Follow {
                        origin_uuid: event_id.clone(),
                        chain: new_chain,
                    },
                };
                // We use the NPC variant since adding [queued] will be confusing.
                queue_command_for_npc(&ctx.trans, &mut player_item, &new_movement).await?;
            }

            player_item.following = Some(FollowData {
                follow_whom: follow_whom.refstr(),
                state: FollowState::Active,
            });
            ctx.trans
                .queue_for_session(
                    &ctx.session,
                    Some(&format!(
                        "You are now following {}.\n",
                        &follow_whom.display_for_sentence(1, false)
                    )),
                )
                .await?;
            ctx.trans.save_item_model(&player_item).await?;
        } else {
            stop_following(&ctx.trans, &mut player_item).await?;
            ctx.trans.save_item_model(&player_item).await?;
        }
        Ok(())
    }
}
static VERB_INT: Verb = Verb;
pub static VERB: UserVerbRef = &VERB_INT as UserVerbRef;

#[cfg(test)]
mod test {
    use uuid::Uuid;

    use super::*;
    use crate::db::MockDBTrans;
    use std::sync::Arc;

    #[test]
    fn propagating_to_overflowing_queue_works() {
        let mut trans = MockDBTrans::default();
        let leader: Item = Item {
            item_type: "test".to_owned(),
            item_code: "test1".to_owned(),
            ..Default::default()
        };
        let source = MovementSource::Command {
            event_id: Uuid::parse_str("ed25224e-9925-4635-8e4f-e612376ef6e9").unwrap(),
        };
        let follower: Item = Item {
            item_type: "test".to_owned(),
            item_code: "test2".to_owned(),
            queue: std::iter::repeat(QueueCommand::Movement {
                direction: Direction::NORTH,
                source: source.clone(),
            })
            .take(20)
            .collect(),
            following: Some(FollowData {
                follow_whom: "test/test1".to_owned(),
                state: FollowState::Active,
            }),
            ..Default::default()
        };

        trans
            .expect_find_followers_by_leader()
            .times(1)
            .withf(|m| m == "test/test1")
            .returning(move |_| Ok(vec![Arc::new(follower.clone())]));

        trans
            .expect_save_item_model()
            .times(1)
            .withf(|i| {
                &i.item_code == "test2"
                    && i.queue.len() == 20
                    && i.following
                        == Some(FollowData {
                            follow_whom: "test/test1".to_owned(),
                            state: FollowState::IfSameRoom,
                        })
            })
            .returning(|_| Ok(()));

        assert!(tokio_test::block_on(propagate_move_to_followers(
            &trans,
            &leader,
            &Direction::NORTH,
            &source
        ))
        .is_ok());
    }
}