use crate::command::context::CommandContext;
use crate::command::handler::{CommandHandler, CommandMetadata};
use crate::command::handlers::list_topics::TopicSummary;
use crate::command::response::{CommandError, CommandResponse, MessageKind};
use crate::command::Command;
use crate::storage::SessionStore;
use async_trait::async_trait;
use std::sync::Arc;

/// 重命名话题命令处理器
pub struct RenameTopicCommandHandler {
    store: Arc<SessionStore>,
}

impl RenameTopicCommandHandler {
    pub fn new(store: Arc<SessionStore>) -> Self {
        Self { store }
    }
}

#[async_trait]
impl CommandHandler for RenameTopicCommandHandler {
    fn can_handle(&self, cmd: &Command) -> bool {
        matches!(cmd, Command::RenameTopic { .. })
    }

    fn metadata(&self) -> Option<CommandMetadata> {
        Some(CommandMetadata {
            name: "rename",
            description: "重命名指定话题",
            usage: "/rename <topic_id> <new_title>",
        })
    }

    async fn handle(
        &self,
        cmd: Command,
        ctx: CommandContext,
    ) -> Result<CommandResponse, CommandError> {
        match cmd {
            Command::RenameTopic { topic_id, title } => {
                handle_rename_topic(self, topic_id, title, ctx).await
            }
            _ => unreachable!(),
        }
    }
}

async fn handle_rename_topic(
    handler: &RenameTopicCommandHandler,
    topic_id: String,
    title: String,
    ctx: CommandContext,
) -> Result<CommandResponse, CommandError> {
    let session_id = ctx
        .session_id
        .as_deref()
        .ok_or_else(|| CommandError::new("NO_SESSION", "No active session"))?;

    // 校验新标题非空
    let trimmed_title = title.trim();
    if trimmed_title.is_empty() {
        return Err(CommandError::new(
            "INVALID_TITLE",
            "Topic title must not be empty",
        ));
    }

    // 验证话题存在
    let topic = handler
        .store
        .get_topic(&topic_id)
        .map_err(|e| CommandError::new("GET_TOPIC_ERROR", e.to_string()))?
        .ok_or_else(|| {
            CommandError::new("TOPIC_NOT_FOUND", format!("Topic not found: {}", topic_id))
        })?;

    let old_title = topic.title.clone();

    // 标题未变化时直接返回当前列表，避免无意义写入
    if old_title == trimmed_title {
        let topics = handler
            .store
            .list_topics(session_id)
            .map_err(|e| CommandError::new("LIST_TOPICS_ERROR", e.to_string()))?;
        let topic_summaries = serialize_summaries(&topics);

        return Ok(CommandResponse::success(ctx.request_id)
            .with_message(MessageKind::Notification, &format!("✓ 话题标题未变化: {}", trimmed_title))
            .with_metadata("topics", &topic_summaries)
            .with_metadata("topic_id", &topic_id)
            .with_metadata("title", trimmed_title)
            .with_metadata("session_id", session_id));
    }

    // 执行重命名（存储层方法已存在）
    handler
        .store
        .update_topic_title(&topic_id, trimmed_title)
        .map_err(|e| CommandError::new("RENAME_TOPIC_ERROR", e.to_string()))?;

    // 查询更新后的话题列表，返回给前端刷新侧边栏
    let topics = handler
        .store
        .list_topics(session_id)
        .map_err(|e| CommandError::new("LIST_TOPICS_ERROR", e.to_string()))?;

    let topic_summaries = serialize_summaries(&topics);

    let message = format!("✓ 已重命名话题: {} → {}", old_title, trimmed_title);

    Ok(CommandResponse::success(ctx.request_id)
        .with_message(MessageKind::Notification, &message)
        .with_metadata("topics", &topic_summaries)
        .with_metadata("topic_id", &topic_id)
        .with_metadata("title", trimmed_title)
        .with_metadata("session_id", session_id))
}

fn serialize_summaries(topics: &[crate::storage::TopicRecord]) -> String {
    let summaries: Vec<TopicSummary> = topics
        .iter()
        .map(|t| TopicSummary {
            topic_id: t.id.clone(),
            session_id: t.session_id.clone(),
            title: t.title.clone(),
            description: t.description.clone().filter(|d| !d.is_empty()),
            message_count: t.message_count,
            created_at: t.created_at,
            last_active_at: t.last_active_at,
        })
        .collect();
    serde_json::to_string(&summaries).unwrap_or_else(|_| "[]".to_string())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::storage::SessionStore;

    fn create_test_handler() -> RenameTopicCommandHandler {
        let store = Arc::new(SessionStore::in_memory().unwrap());
        RenameTopicCommandHandler::new(store)
    }

    #[tokio::test]
    async fn test_rename_topic_success() {
        let handler = create_test_handler();
        let store = handler.store.clone();

        let session = store.create_session("test_channel", Some("test")).unwrap();
        let topic = store
            .create_topic(&session.id, "old title", None)
            .unwrap();

        let ctx = CommandContext::new("test", "test_channel")
            .with_session_id(&session.id)
            .with_chat_id(&session.id);
        let cmd = Command::RenameTopic {
            topic_id: topic.id.clone(),
            title: "new title".to_string(),
        };

        let result = handler.handle(cmd, ctx).await;
        assert!(result.is_ok());

        let resp = result.unwrap();
        assert!(resp.success);
        assert_eq!(resp.metadata.get("title").map(String::as_str), Some("new title"));
        assert_eq!(resp.metadata.get("topic_id").map(String::as_str), Some(topic.id.as_str()));
        assert!(resp.metadata.contains_key("topics"));

        // 验证存储层已更新
        let updated = store.get_topic(&topic.id).unwrap().unwrap();
        assert_eq!(updated.title, "new title");
    }

    #[tokio::test]
    async fn test_rename_topic_empty_title() {
        let handler = create_test_handler();
        let store = handler.store.clone();

        let session = store.create_session("test_channel", Some("test")).unwrap();
        let topic = store
            .create_topic(&session.id, "old title", None)
            .unwrap();

        let ctx = CommandContext::new("test", "test_channel")
            .with_session_id(&session.id)
            .with_chat_id(&session.id);
        let cmd = Command::RenameTopic {
            topic_id: topic.id.clone(),
            title: "   ".to_string(),
        };

        let result = handler.handle(cmd, ctx).await;
        assert!(result.is_err());
        let err = result.unwrap_err();
        assert_eq!(err.code, "INVALID_TITLE");

        // 标题未被修改
        let unchanged = store.get_topic(&topic.id).unwrap().unwrap();
        assert_eq!(unchanged.title, "old title");
    }

    #[tokio::test]
    async fn test_rename_nonexistent_topic() {
        let handler = create_test_handler();
        let store = handler.store.clone();

        let session = store.create_session("test_channel", Some("test")).unwrap();
        let ctx = CommandContext::new("test", "test_channel")
            .with_session_id(&session.id)
            .with_chat_id(&session.id);
        let cmd = Command::RenameTopic {
            topic_id: "nonexistent".to_string(),
            title: "new title".to_string(),
        };

        let result = handler.handle(cmd, ctx).await;
        assert!(result.is_err());
        let err = result.unwrap_err();
        assert_eq!(err.code, "TOPIC_NOT_FOUND");
    }

    #[tokio::test]
    async fn test_rename_topic_same_title_skips_write() {
        let handler = create_test_handler();
        let store = handler.store.clone();

        let session = store.create_session("test_channel", Some("test")).unwrap();
        let topic = store
            .create_topic(&session.id, "same title", None)
            .unwrap();
        let original_updated_at = store.get_topic(&topic.id).unwrap().unwrap().updated_at;

        // 等待一秒确保 updated_at 会变化（如果真的写入）
        tokio::time::sleep(std::time::Duration::from_secs(1)).await;

        let ctx = CommandContext::new("test", "test_channel")
            .with_session_id(&session.id)
            .with_chat_id(&session.id);
        let cmd = Command::RenameTopic {
            topic_id: topic.id.clone(),
            title: "same title".to_string(),
        };

        let result = handler.handle(cmd, ctx).await;
        assert!(result.is_ok());

        // updated_at 未变化说明未触发写入
        let after = store.get_topic(&topic.id).unwrap().unwrap();
        assert_eq!(after.updated_at, original_updated_at);
    }

    #[test]
    fn test_can_handle() {
        let handler = create_test_handler();
        assert!(handler.can_handle(&Command::RenameTopic {
            topic_id: "test".to_string(),
            title: "test".to_string(),
        }));
        assert!(!handler.can_handle(&Command::Help));
        assert!(!handler.can_handle(&Command::DeleteTopic {
            topic_id: "test".to_string(),
        }));
    }
}