use serde::{Deserialize, Serialize};
use uuid::Uuid;

use crate::error::AppError;
use crate::models::common::SubscriptionLevel;
use crate::models::repos::RepoWatch;
use crate::service::RepoService;
use crate::session::Session;

use super::util::clamp_limit_offset;

#[derive(Deserialize, Serialize, Clone, Debug, utoipa::ToSchema)]
pub struct WatchParams {
    pub level: Option<String>,
}

impl RepoService {
    pub async fn repo_watch(
        &self,
        ctx: &Session,
        wk_name: &str,
        repo_name: &str,
        params: WatchParams,
    ) -> Result<(), AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let repo = self.resolve_repo(wk_name, repo_name).await?;
        let repo_id = repo.id;
        self.ensure_repo_readable(user_uid, &repo).await?;

        let level = params
            .level
            .as_deref()
            .and_then(|v| v.parse::<SubscriptionLevel>().ok())
            .unwrap_or(SubscriptionLevel::Participating);

        if level == SubscriptionLevel::Unknown {
            return Err(AppError::BadRequest("invalid watch level".into()));
        }

        let now = chrono::Utc::now();
        let mut txn = self
            .ctx
            .db
            .writer()
            .begin()
            .await
            .map_err(|_| AppError::TxnError)?;
        sqlx::query("SET LOCAL app.current_user_id = $1")
            .bind(user_uid)
            .execute(&mut *txn)
            .await
            .map_err(AppError::Database)?;

        let existing = sqlx::query_scalar::<_, bool>(
            "SELECT EXISTS(SELECT 1 FROM repo_watch WHERE repo_id = $1 AND user_id = $2)",
        )
        .bind(repo_id)
        .bind(user_uid)
        .fetch_one(self.ctx.db.reader())
        .await
        .map_err(AppError::Database)?;

        if existing {
            sqlx::query("UPDATE repo_watch SET level = $1, updated_at = $2 WHERE repo_id = $3 AND user_id = $4")
                .bind(level.to_string())
                .bind(now)
                .bind(repo_id)
                .bind(user_uid)
                .execute(&mut *txn)
                .await
                .map_err(AppError::Database)?;
        } else {
            sqlx::query("INSERT INTO repo_watch (id, repo_id, user_id, level, created_at, updated_at) VALUES ($1, $2, $3, $4, $5, $5)")
                .bind(Uuid::now_v7())
                .bind(repo_id)
                .bind(user_uid)
                .bind(level.to_string())
                .bind(now)
                .execute(&mut *txn)
                .await
                .map_err(AppError::Database)?;

            sqlx::query(
                "UPDATE repo_stats SET watchers_count = watchers_count + 1, updated_at = $1 WHERE repo_id = $2",
            )
            .bind(now)
            .bind(repo_id)
            .execute(&mut *txn)
            .await
            .map_err(AppError::Database)?;
        }

        txn.commit().await.map_err(|_| AppError::TxnError)?;
        Ok(())
    }

    pub async fn repo_unwatch(
        &self,
        ctx: &Session,
        wk_name: &str,
        repo_name: &str,
    ) -> Result<(), AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let repo = self.resolve_repo(wk_name, repo_name).await?;
        let repo_id = repo.id;
        let now = chrono::Utc::now();

        let mut txn = self
            .ctx
            .db
            .writer()
            .begin()
            .await
            .map_err(|_| AppError::TxnError)?;
        sqlx::query("SET LOCAL app.current_user_id = $1")
            .bind(user_uid)
            .execute(&mut *txn)
            .await
            .map_err(AppError::Database)?;

        let result = sqlx::query("DELETE FROM repo_watch WHERE repo_id = $1 AND user_id = $2")
            .bind(repo_id)
            .bind(user_uid)
            .execute(&mut *txn)
            .await
            .map_err(AppError::Database)?;

        if result.rows_affected() > 0 {
            sqlx::query(
                "UPDATE repo_stats SET watchers_count = GREATEST(watchers_count - 1, 0), updated_at = $1 WHERE repo_id = $2",
            )
            .bind(now)
            .bind(repo_id)
            .execute(&mut *txn)
            .await
            .map_err(AppError::Database)?;
        }

        txn.commit().await.map_err(|_| AppError::TxnError)?;
        Ok(())
    }

    pub async fn repo_watchers(
        &self,
        ctx: &Session,
        wk_name: &str,
        repo_name: &str,
        limit: i64,
        offset: i64,
    ) -> Result<Vec<RepoWatch>, AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let repo = self.resolve_repo(wk_name, repo_name).await?;
        let repo_id = repo.id;
        self.ensure_repo_readable(user_uid, &repo).await?;
        let (limit, offset) = clamp_limit_offset(limit, offset);
        sqlx::query_as::<_, RepoWatch>(
            "SELECT id, repo_id, user_id, level, created_at, updated_at FROM repo_watch WHERE repo_id = $1 ORDER BY created_at DESC LIMIT $2 OFFSET $3",
        )
        .bind(repo_id)
        .bind(limit)
        .bind(offset)
        .fetch_all(self.ctx.db.reader())
        .await
        .map_err(AppError::Database)
    }
}