use uuid::Uuid;

use crate::error::AppError;
use crate::models::common::{Role, State};
use crate::models::issues::IssueMilestone;
use crate::service::IssueService;
use crate::session::Session;

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

#[derive(serde::Deserialize, serde::Serialize, Clone, Debug, utoipa::ToSchema)]
pub struct CreateMilestoneParams {
    pub title: String,
    pub description: Option<String>,
    pub due_at: Option<chrono::DateTime<chrono::Utc>>,
}

#[derive(serde::Deserialize, serde::Serialize, Clone, Debug, utoipa::ToSchema)]
pub struct UpdateMilestoneParams {
    pub title: Option<String>,
    pub description: Option<String>,
    pub due_at: Option<chrono::DateTime<chrono::Utc>>,
    pub state: Option<String>,
}

impl IssueService {
    pub async fn issue_milestones(
        &self,
        ctx: &Session,
        wk_name: &str,
        repo_name: &str,
        limit: i64,
        offset: i64,
    ) -> Result<Vec<IssueMilestone>, AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let repo_id = self.resolve_repo_id(wk_name, repo_name).await?;
        let repo = crate::models::repos::Repo::find_by_id(self.ctx.db.reader(), repo_id)
            .await
            .map_err(AppError::Database)?
            .ok_or(AppError::NotFound("repo not found".into()))?;
        self.ensure_repo_readable(user_uid, &repo).await?;
        let (limit, offset) = clamp_limit_offset(limit, offset);
        sqlx::query_as::<_, IssueMilestone>(
            "SELECT id, repo_id, title, description, state, due_at, closed_at, created_by, \
             created_at, updated_at FROM issue_milestone WHERE repo_id = $1 \
             ORDER BY state ASC, due_at ASC NULLS LAST LIMIT $2 OFFSET $3",
        )
        .bind(repo_id)
        .bind(limit)
        .bind(offset)
        .fetch_all(self.ctx.db.reader())
        .await
        .map_err(AppError::Database)
    }

    pub async fn issue_create_milestone(
        &self,
        ctx: &Session,
        wk_name: &str,
        repo_name: &str,
        params: CreateMilestoneParams,
    ) -> Result<IssueMilestone, AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let repo_id = self.resolve_repo_id(wk_name, repo_name).await?;
        self.ensure_repo_role(repo_id, user_uid, Role::Member)
            .await?;
        let title = required_text(params.title, "title")?;
        let now = chrono::Utc::now();
        sqlx::query_as::<_, IssueMilestone>(
            "INSERT INTO issue_milestone (id, repo_id, title, description, state, due_at, closed_at, \
             created_by, created_at, updated_at) VALUES ($1, $2, $3, $4, 'open', $5, NULL, $6, $7, $7) \
             RETURNING id, repo_id, title, description, state, due_at, closed_at, created_by, created_at, updated_at",
        )
        .bind(Uuid::now_v7()).bind(repo_id).bind(&title).bind(params.description.as_deref())
        .bind(params.due_at).bind(user_uid).bind(now)
        .fetch_one(self.ctx.db.writer()).await.map_err(AppError::Database)
    }

    pub async fn issue_update_milestone(
        &self,
        ctx: &Session,
        wk_name: &str,
        repo_name: &str,
        milestone_id: Uuid,
        params: UpdateMilestoneParams,
    ) -> Result<IssueMilestone, AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let repo_id = self.resolve_repo_id(wk_name, repo_name).await?;
        self.ensure_repo_role(repo_id, user_uid, Role::Member)
            .await?;
        let current = sqlx::query_as::<_, IssueMilestone>(
            "SELECT id, repo_id, title, description, state, due_at, closed_at, created_by, created_at, updated_at \
             FROM issue_milestone WHERE id = $1 AND repo_id = $2",
        )
        .bind(milestone_id).bind(repo_id).fetch_optional(self.ctx.db.reader()).await
        .map_err(AppError::Database)?.ok_or(AppError::NotFound("milestone not found".into()))?;

        let title = params.title.unwrap_or(current.title);
        let description = merge_optional_text(params.description, current.description);
        let due_at = params.due_at.or(current.due_at);
        let now = chrono::Utc::now();

        let (state, closed_at) = match params.state.as_deref() {
            Some("closed") if current.state != State::Closed => (State::Closed, Some(now)),
            Some("open") if current.state != State::Open => (State::Open, None),
            _ => (current.state, current.closed_at),
        };

        sqlx::query_as::<_, IssueMilestone>(
            "UPDATE issue_milestone SET title = $1, description = $2, state = $3, due_at = $4, \
             closed_at = $5, updated_at = $6 WHERE id = $7 \
             RETURNING id, repo_id, title, description, state, due_at, closed_at, created_by, created_at, updated_at",
        )
        .bind(&title).bind(&description).bind(state).bind(due_at).bind(closed_at).bind(now).bind(milestone_id)
        .fetch_one(self.ctx.db.writer()).await.map_err(AppError::Database)
    }

    pub async fn issue_delete_milestone(
        &self,
        ctx: &Session,
        wk_name: &str,
        repo_name: &str,
        milestone_id: Uuid,
    ) -> Result<(), AppError> {
        let user_uid = ctx.user().ok_or(AppError::Unauthorized)?;
        let repo_id = self.resolve_repo_id(wk_name, repo_name).await?;
        self.ensure_repo_role(repo_id, user_uid, Role::Admin)
            .await?;

        let mut txn = self
            .ctx
            .db
            .writer()
            .begin()
            .await
            .map_err(|_| AppError::TxnError)?;

        // Clear milestone_id from all issues that reference this milestone
        sqlx::query(
            "UPDATE issue SET milestone_id = NULL, updated_at = $1 WHERE milestone_id = $2",
        )
        .bind(chrono::Utc::now())
        .bind(milestone_id)
        .execute(&mut *txn)
        .await
        .map_err(AppError::Database)?;

        let result = sqlx::query("DELETE FROM issue_milestone WHERE id = $1 AND repo_id = $2")
            .bind(milestone_id)
            .bind(repo_id)
            .execute(&mut *txn)
            .await
            .map_err(AppError::Database)?;
        ensure_affected(result.rows_affected(), "milestone not found")?;

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