use chrono::TimeDelta;
use sqlx::sqlite::SqlitePool;

use super::{Id, Invite, Summary, repo::Provider as _};
use crate::{
    clock::DateTime,
    db::{self, NotFound as _},
    error::failed::{ErrorExt as _, Failed, ResultExt as _},
    event::{Broadcaster, repo::Provider as _},
    login::Login,
    name::Name,
    password::Password,
    token::{Secret, Token, repo::Provider as _},
    user::{self, create, create::Create, repo::Provider as _},
};

pub struct Invites {
    db: SqlitePool,
    events: Broadcaster,
}

impl Invites {
    pub const fn new(db: SqlitePool, events: Broadcaster) -> Self {
        Self { db, events }
    }

    pub async fn issue(&self, issuer: &Login, issued_at: &DateTime) -> Result<Invite, IssueError> {
        let issuer_not_found = || IssueError::IssuerNotFound(issuer.id.clone().into());
        let issuer_deleted = || IssueError::IssuerDeleted(issuer.id.clone().into());

        let mut tx = self.db.begin().await.fail(db::failed::BEGIN)?;
        let issuer = tx
            .users()
            .by_login(issuer)
            .await
            .optional()
            .fail("Failed to load issuing user")?
            .ok_or_else(issuer_not_found)?;
        let now = tx
            .sequence()
            .current()
            .await
            .fail("Failed to find event sequence number")?;
        let issuer = issuer.as_of(now).ok_or_else(issuer_deleted)?;
        let invite = tx
            .invites()
            .create(&issuer, issued_at)
            .await
            .fail("Failed to store new invitation")?;
        tx.commit().await.fail(db::failed::COMMIT)?;

        Ok(invite)
    }

    pub async fn get(&self, invite: &Id) -> Result<Option<Summary>, sqlx::Error> {
        let mut tx = self.db.begin().await?;
        let invite = tx.invites().summary(invite).await.optional()?;
        tx.commit().await?;

        Ok(invite)
    }

    pub async fn accept(
        &self,
        invite: &Id,
        name: &Name,
        password: &Password,
        accepted_at: &DateTime,
    ) -> Result<Secret, AcceptError> {
        let to_not_found = || AcceptError::NotFound(invite.clone());

        let create = Create::begin(name, password, accepted_at);

        let mut tx = self.db.begin().await.fail(db::failed::BEGIN)?;
        let invite = tx
            .invites()
            .by_id(invite)
            .await
            .optional()
            .fail("Failed to load invitation")?
            .ok_or_else(to_not_found)?;
        // Split the tx here so we don't block writes while we deal with the password,
        // and don't deal with the password until we're fairly confident we can accept
        // the invite. Final validation is in the next tx.
        tx.commit().await.fail(db::failed::COMMIT)?;

        let validated = create.validate().map_err(|err| match err {
            create::Error::InvalidName(name) => AcceptError::InvalidName(name),
            create::Error::Failed(_) => err.fail("Failed to validate invited user"),
        })?;

        let mut tx = self.db.begin().await.fail(db::failed::BEGIN)?;
        // If the invite has been deleted or accepted in the interim, this step will
        // catch it.
        tx.invites()
            .accept(&invite)
            .await
            .fail("Failed to remove accepted invitation")?;
        let stored =
            validated
                .store(&mut tx)
                .await
                .map_err(|err| match err.as_database_error() {
                    Some(err) if err.is_unique_violation() => {
                        AcceptError::DuplicateLogin(name.clone())
                    }
                    _ => err.fail("Failed to store invited user"),
                })?;
        let login = stored.login();
        let (token, secret) = Token::generate(login, accepted_at);
        tx.tokens()
            .create(&token, &secret)
            .await
            .fail("Failed to issue token for invited user")?;
        tx.commit().await.fail(db::failed::COMMIT)?;

        stored.publish(&self.events);

        Ok(secret)
    }

    pub async fn expire(&self, relative_to: &DateTime) -> Result<(), sqlx::Error> {
        // Somewhat arbitrarily, expire after one day.
        let expire_at = relative_to.to_owned() - TimeDelta::days(1);

        let mut tx = self.db.begin().await?;
        tx.invites().expire(&expire_at).await?;
        tx.commit().await?;

        Ok(())
    }
}

#[derive(Debug, thiserror::Error)]
pub enum IssueError {
    #[error("issuing user {0} not found")]
    IssuerNotFound(user::Id),
    #[error("issuing user {0} deleted")]
    IssuerDeleted(user::Id),
    #[error(transparent)]
    Failed(#[from] Failed),
}

#[derive(Debug, thiserror::Error)]
pub enum AcceptError {
    #[error("invite not found: {0}")]
    NotFound(Id),
    #[error("invalid user name: {0}")]
    InvalidName(Name),
    #[error("name in use: {0}")]
    DuplicateLogin(Name),
    #[error(transparent)]
    Failed(#[from] Failed),
}