use chrono::{DateTime, Utc};
use sqlx::{FromRow, SqlitePool};
use uuid::Uuid;

use crate::{
    error::{ApiError, ApiResult},
    python_mirrors::{
        model::{DefaultPythonMirror, PythonMirrorResponse},
        service::ValidatedMirror,
    },
};

#[derive(Debug, FromRow)]
struct MirrorRow {
    id: String,
    name: String,
    index_url: String,
    trusted_host: Option<String>,
    enabled: bool,
    is_default: bool,
    created_at: DateTime<Utc>,
    updated_at: DateTime<Utc>,
}

impl From<MirrorRow> for PythonMirrorResponse {
    fn from(row: MirrorRow) -> Self {
        Self {
            id: row.id,
            name: row.name,
            index_url: row.index_url,
            trusted_host: row.trusted_host,
            enabled: row.enabled,
            is_default: row.is_default,
            created_at: row.created_at,
            updated_at: row.updated_at,
        }
    }
}

pub async fn list(pool: &SqlitePool) -> ApiResult<Vec<PythonMirrorResponse>> {
    let rows = sqlx::query_as::<_, MirrorRow>(
        "SELECT id, name, index_url, trusted_host, enabled, is_default, created_at, updated_at
         FROM python_mirrors
         ORDER BY is_default DESC, enabled DESC, name COLLATE NOCASE ASC",
    )
    .fetch_all(pool)
    .await?;
    Ok(rows.into_iter().map(Into::into).collect())
}

pub async fn get(pool: &SqlitePool, id: &str) -> ApiResult<PythonMirrorResponse> {
    let row = sqlx::query_as::<_, MirrorRow>(
        "SELECT id, name, index_url, trusted_host, enabled, is_default, created_at, updated_at
         FROM python_mirrors WHERE id = ?",
    )
    .bind(id)
    .fetch_optional(pool)
    .await?
    .ok_or_else(|| ApiError::mirror_not_found(format!("镜像 {id} 不存在")))?;
    Ok(row.into())
}

pub async fn create(pool: &SqlitePool, input: ValidatedMirror) -> ApiResult<PythonMirrorResponse> {
    if index_url_exists(pool, &input.index_url, None).await? {
        return Err(ApiError::mirror_conflict("该索引地址已经存在"));
    }

    let id = Uuid::new_v4().simple().to_string();
    let now = Utc::now();
    sqlx::query(
        "INSERT INTO python_mirrors
            (id, name, index_url, trusted_host, enabled, is_default, created_at, updated_at)
         VALUES (?, ?, ?, ?, ?, 0, ?, ?)",
    )
    .bind(&id)
    .bind(&input.name)
    .bind(&input.index_url)
    .bind(input.trusted_host.as_deref())
    .bind(input.enabled)
    .bind(now)
    .bind(now)
    .execute(pool)
    .await
    .map_err(map_mirror_error)?;

    get(pool, &id).await
}

pub async fn update(
    pool: &SqlitePool,
    id: &str,
    input: ValidatedMirror,
) -> ApiResult<PythonMirrorResponse> {
    if index_url_exists(pool, &input.index_url, Some(id)).await? {
        return Err(ApiError::mirror_conflict("该索引地址已经存在"));
    }

    let now = Utc::now();
    let result = sqlx::query(
        "UPDATE python_mirrors
         SET name = ?, index_url = ?, trusted_host = ?, enabled = ?,
             is_default = CASE WHEN ? = 0 THEN 0 ELSE is_default END,
             updated_at = ?
         WHERE id = ?",
    )
    .bind(&input.name)
    .bind(&input.index_url)
    .bind(input.trusted_host.as_deref())
    .bind(input.enabled)
    .bind(input.enabled)
    .bind(now)
    .bind(id)
    .execute(pool)
    .await
    .map_err(map_mirror_error)?;

    if result.rows_affected() == 0 {
        return Err(ApiError::mirror_not_found(format!("镜像 {id} 不存在")));
    }
    get(pool, id).await
}

pub async fn delete(pool: &SqlitePool, id: &str) -> ApiResult<()> {
    let result = sqlx::query("DELETE FROM python_mirrors WHERE id = ?")
        .bind(id)
        .execute(pool)
        .await?;
    if result.rows_affected() == 0 {
        return Err(ApiError::mirror_not_found(format!("镜像 {id} 不存在")));
    }
    Ok(())
}

/// 设为默认：同一事务里先清掉旧默认，再把目标设为默认并启用。
pub async fn set_default(pool: &SqlitePool, id: &str) -> ApiResult<PythonMirrorResponse> {
    let now = Utc::now();
    let mut transaction = pool.begin().await?;

    let exists: Option<(i64,)> = sqlx::query_as("SELECT 1 FROM python_mirrors WHERE id = ?")
        .bind(id)
        .fetch_optional(&mut *transaction)
        .await?;
    if exists.is_none() {
        transaction.rollback().await?;
        return Err(ApiError::mirror_not_found(format!("镜像 {id} 不存在")));
    }

    sqlx::query("UPDATE python_mirrors SET is_default = 0, updated_at = ? WHERE is_default = 1")
        .bind(now)
        .execute(&mut *transaction)
        .await?;
    sqlx::query(
        "UPDATE python_mirrors SET is_default = 1, enabled = 1, updated_at = ? WHERE id = ?",
    )
    .bind(now)
    .bind(id)
    .execute(&mut *transaction)
    .await?;
    transaction.commit().await?;

    get(pool, id).await
}

/// 执行器读取：只返回「启用且是默认」的镜像。
pub async fn default_enabled(pool: &SqlitePool) -> ApiResult<Option<DefaultPythonMirror>> {
    let row = sqlx::query_as::<_, (String, String, Option<String>)>(
        "SELECT name, index_url, trusted_host
         FROM python_mirrors
         WHERE enabled = 1 AND is_default = 1
         LIMIT 1",
    )
    .fetch_optional(pool)
    .await?;
    Ok(
        row.map(|(name, index_url, trusted_host)| DefaultPythonMirror {
            name,
            index_url,
            trusted_host,
        }),
    )
}

async fn index_url_exists(
    pool: &SqlitePool,
    index_url: &str,
    excluding_id: Option<&str>,
) -> ApiResult<bool> {
    let existing: Option<(String,)> = match excluding_id {
        Some(id) => {
            sqlx::query_as(
                "SELECT id FROM python_mirrors WHERE lower(index_url) = lower(?) AND id <> ?",
            )
            .bind(index_url)
            .bind(id)
            .fetch_optional(pool)
            .await?
        }
        None => {
            sqlx::query_as("SELECT id FROM python_mirrors WHERE lower(index_url) = lower(?)")
                .bind(index_url)
                .fetch_optional(pool)
                .await?
        }
    };
    Ok(existing.is_some())
}

fn map_mirror_error(error: sqlx::Error) -> ApiError {
    if let sqlx::Error::Database(database_error) = &error
        && database_error.is_unique_violation()
    {
        return ApiError::mirror_conflict("该索引地址已经存在");
    }
    ApiError::from(error)
}