pub mod handler;
pub mod updates;

use std::any::Any;
use std::sync::Arc;

use anyhow::Context;
use giterated_models::error::OperationError;
use giterated_models::instance::Instance;
use giterated_models::object::{GiteratedObject, Object, ObjectRequestError};
use giterated_models::object_backend::ObjectBackend;
use giterated_models::operation::GiteratedOperation;
use giterated_models::repository::{DefaultBranch, Description, Repository, Visibility};
use giterated_models::user::{Bio, DisplayName, User};
use giterated_stack::provider::MetadataProvider;
use giterated_stack::{GiteratedStack, ObjectMeta, SubstackBuilder};
use giterated_stack::{SettingMeta, StackOperationState};
use serde_json::Value;
use sqlx::PgPool;
use std::fmt::Debug;
use tokio::sync::{Mutex, OnceCell};

use crate::backend::settings::{RepositorySettingRow, UserSettingRow};
use crate::backend::{RepositoryBackend, UserBackend};

use self::handler::{
    instance_authentication_request, instance_create_repository_request,
    instance_registration_request, repository_commit_before, repository_commit_by_id,
    repository_diff, repository_diff_patch, repository_file_from_id, repository_file_from_path,
    repository_get_branches, repository_get_default_branch, repository_get_latest_commit,
    repository_get_statistics, repository_get_value_description, repository_get_value_visibility,
    repository_info, repository_last_commit_of_file, user_get_repositories, user_get_value_bio,
    user_get_value_display_name,
};

#[derive(Clone, Debug)]
pub struct Foobackend {}

#[async_trait::async_trait(?Send)]
impl ObjectBackend<StackOperationState> for Foobackend {
    async fn object_operation<O: GiteratedObject + Debug, D: GiteratedOperation<O> + Debug>(
        &self,
        _object: O,
        _operation: &str,
        _payload: D,
        _operation_state: &StackOperationState,
    ) -> Result<D::Success, OperationError<D::Failure>> {
        // We don't handle operations with this backend
        Err(OperationError::Unhandled)
    }

    async fn get_object<O: GiteratedObject + Debug>(
        &self,
        _object_str: &str,
        _operation_state: &StackOperationState,
    ) -> Result<Object<StackOperationState, O, Self>, OperationError<ObjectRequestError>> {
        Err(OperationError::Unhandled)
    }
}

/// A backend implementation which attempts to resolve data from the instance's database.
#[derive(Clone)]
#[allow(unused)]
pub struct DatabaseBackend {
    pub(self) our_instance: Instance,
    pub(self) pool: PgPool,
    pub(self) user_backend: Arc<Mutex<dyn UserBackend + Send>>,
    pub(self) repository_backend: Arc<Mutex<dyn RepositoryBackend + Send>>,
    pub stack: Arc<OnceCell<Arc<GiteratedStack>>>,
}

impl DatabaseBackend {
    pub fn new(
        instance: Instance,
        user_backend: Arc<Mutex<dyn UserBackend + Send>>,
        repository_backend: Arc<Mutex<dyn RepositoryBackend + Send>>,
        pool: PgPool,
        stack: Arc<OnceCell<Arc<GiteratedStack>>>,
    ) -> Self {
        Self {
            our_instance: instance,
            user_backend,
            repository_backend,
            pool,
            stack,
        }
    }

    pub fn into_substack(self) -> SubstackBuilder<Self> {
        let mut builder = SubstackBuilder::<Self>::new(self.clone());

        builder.object_metadata_provider(Box::new(self));

        builder
            .object::<Repository>()
            .object::<User>()
            .object::<Instance>();

        // Register value settings, which are settings that directly correspond to
        // value types.
        builder
            .value_setting::<User, DisplayName>()
            .value_setting::<User, Bio>()
            .value_setting::<Repository, Description>()
            .value_setting::<Repository, Visibility>()
            .value_setting::<Repository, DefaultBranch>();

        builder
            .value(user_get_value_bio)
            .value(user_get_value_display_name)
            .value(repository_get_value_description)
            .value(repository_get_value_visibility)
            .value(repository_get_default_branch)
            .value(repository_get_latest_commit);

        builder
            .operation(user_get_repositories)
            .operation(instance_registration_request)
            .operation(instance_authentication_request)
            .operation(instance_create_repository_request)
            .operation(repository_info)
            .operation(repository_get_statistics)
            .operation(repository_file_from_id)
            .operation(repository_file_from_path)
            .operation(repository_last_commit_of_file)
            .operation(repository_commit_by_id)
            .operation(repository_diff)
            .operation(repository_diff_patch)
            .operation(repository_commit_before)
            .operation(repository_get_branches);

        builder
    }
}

impl Debug for DatabaseBackend {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("DatabaseBackend").finish()
    }
}

#[async_trait::async_trait]
impl MetadataProvider for DatabaseBackend {
    fn provides_for(&self, object: &dyn Any) -> bool {
        object.is::<Instance>() || object.is::<Repository>() || object.is::<User>()
    }

    async fn write(
        &self,
        object: &(dyn Any + Send + Sync),
        _object_meta: &ObjectMeta,
        setting: &(dyn Any + Send + Sync),
        setting_meta: &SettingMeta,
    ) -> Result<(), anyhow::Error> {
        if let Some(repository) = object.downcast_ref::<Repository>() {
            sqlx::query!("INSERT INTO repository_settings VALUES ($1, $2, $3) ON CONFLICT (repository, name) DO UPDATE SET value = $3",
        repository.to_string(), setting_meta.name, serde_json::to_string(&(setting_meta.serialize)(setting).unwrap())?)
            .execute(&self.pool).await?;

            Ok(())
        } else if let Some(user) = object.downcast_ref::<User>() {
            sqlx::query!("INSERT INTO user_settings VALUES ($1, $2, $3) ON CONFLICT (username, name) DO UPDATE SET value = $3",
            user.username, setting_meta.name, serde_json::to_string(&(setting_meta.serialize)(setting).unwrap())?)
            .execute(&self.pool).await?;

            Ok(())
        } else {
            unreachable!()
        }
    }

    async fn read(
        &self,
        object: &(dyn Any + Send + Sync),
        _object_meta: &ObjectMeta,
        setting_meta: &SettingMeta,
    ) -> Result<Value, anyhow::Error> {
        if let Some(repository) = object.downcast_ref::<Repository>() {
            let row = sqlx::query_as!(
                RepositorySettingRow,
                "SELECT * FROM repository_settings WHERE repository = $1 AND name = $2",
                repository.to_string(),
                setting_meta.name
            )
            .fetch_one(&self.pool)
            .await?;

            let setting =
                serde_json::from_str(&row.value).context("deserializing setting from database")?;

            Ok(setting)
        } else if let Some(user) = object.downcast_ref::<User>() {
            info!("User for {}", setting_meta.name);
            let row = sqlx::query_as!(
                UserSettingRow,
                "SELECT * FROM user_settings WHERE username = $1 AND name = $2",
                user.username,
                setting_meta.name
            )
            .fetch_one(&self.pool)
            .await?;

            let setting =
                serde_json::from_str(&row.value).context("deserializing setting from database")?;

            Ok(setting)
        } else {
            unreachable!()
        }
    }
}