use uuid::Uuid;

use crate::error::AppError;
use crate::models::issues::IssueAssignee;
use crate::service::IssueService;
use crate::session::Session;

use super::util::{clamp_limit_offset, ensure_affected};

impl IssueService {
    pub async fn issue_assignees(
        &self,
        ctx: &Session,
        wk_name: &str,
        number: i64,
        limit: i64,
        offset: i64,
    ) -> Result<Vec<IssueAssignee>, AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let issue = self.resolve_issue(wk_name, number).await?;
        let issue_id = issue.id;
        self.ensure_issue_readable(user_uid, &issue).await?;
        let (limit, offset) = clamp_limit_offset(limit, offset);
        sqlx::query_as::<_, IssueAssignee>(
            "SELECT id, issue_id, assignee_id, assigned_by, created_at \
             FROM issue_assignee WHERE issue_id = $1 ORDER BY created_at ASC LIMIT $2 OFFSET $3",
        )
        .bind(issue_id)
        .bind(limit)
        .bind(offset)
        .fetch_all(self.ctx.db.reader())
        .await
        .map_err(AppError::Database)
    }

    pub async fn issue_assign(
        &self,
        ctx: &Session,
        wk_name: &str,
        number: i64,
        assignee_id: Uuid,
    ) -> Result<IssueAssignee, AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let issue = self.resolve_issue(wk_name, number).await?;
        let issue_id = issue.id;
        self.ensure_issue_editable(user_uid, &issue).await?;
        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 assignee = sqlx::query_as::<_, IssueAssignee>(
            "INSERT INTO issue_assignee (id, issue_id, assignee_id, assigned_by, created_at) \
             VALUES ($1, $2, $3, $4, $5) ON CONFLICT (issue_id, assignee_id) DO NOTHING \
             RETURNING id, issue_id, assignee_id, assigned_by, created_at",
        )
        .bind(Uuid::now_v7())
        .bind(issue_id)
        .bind(assignee_id)
        .bind(user_uid)
        .bind(now)
        .fetch_optional(&mut *txn)
        .await
        .map_err(AppError::Database)?
        .ok_or(AppError::Conflict("user already assigned".into()))?;
        sqlx::query("UPDATE issue_stats SET assignees_count = assignees_count + 1, updated_at = $1 WHERE issue_id = $2")
            .bind(now).bind(issue_id).execute(&mut *txn).await.map_err(AppError::Database)?;
        sqlx::query(
            "INSERT INTO issue_subscriber (id, issue_id, user_id, reason, muted, created_at, updated_at) \
             VALUES ($1, $2, $3, 'assignee', false, $4, $4) ON CONFLICT DO NOTHING",
        )
        .bind(Uuid::now_v7()).bind(issue_id).bind(assignee_id).bind(now)
        .execute(&mut *txn).await.map_err(AppError::Database)?;
        txn.commit().await.map_err(|_| AppError::TxnError)?;
        Ok(assignee)
    }

    pub async fn issue_unassign(
        &self,
        ctx: &Session,
        wk_name: &str,
        number: i64,
        assignee_id: Uuid,
    ) -> Result<(), AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let issue = self.resolve_issue(wk_name, number).await?;
        let issue_id = issue.id;
        self.ensure_issue_editable(user_uid, &issue).await?;
        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 issue_assignee WHERE issue_id = $1 AND assignee_id = $2")
                .bind(issue_id)
                .bind(assignee_id)
                .execute(&mut *txn)
                .await
                .map_err(AppError::Database)?;
        ensure_affected(result.rows_affected(), "assignee not found")?;
        sqlx::query("UPDATE issue_stats SET assignees_count = GREATEST(assignees_count - 1, 0), updated_at = $1 WHERE issue_id = $2")
            .bind(now).bind(issue_id).execute(&mut *txn).await.map_err(AppError::Database)?;
        txn.commit().await.map_err(|_| AppError::TxnError)?;
        Ok(())
    }
}