//! Message read operations — get single, list by channel, list by thread.
//!
//! All list queries use UUID v7 cursor-based pagination (no OFFSET).

use sqlx::Row;
use uuid::Uuid;

use crate::ImksResult;
use crate::models::message::Message;

use super::message_repo::MessageRepo;
use super::pagination::{CursorPage, clamp_limit};

impl MessageRepo {
    /// Fetch a single message by ID.
    ///
    /// Returns `None` if the message doesn't exist or has been soft-deleted.
    pub async fn get(&self, message_id: Uuid) -> ImksResult<Option<Message>> {
        let row = sqlx::query_as::<_, Message>(
            "SELECT * FROM message WHERE id = $1 AND deleted_at IS NULL",
        )
        .bind(message_id)
        .fetch_optional(self.pool())
        .await?;

        Ok(row)
    }

    /// List messages in a channel with cursor-based pagination.
    ///
    /// Returns messages in reverse chronological order (newest first).
    /// Pass `before` as the last message ID from the previous page to
    /// fetch the next page.
    pub async fn list_by_channel(
        &self,
        channel_id: Uuid,
        before: Option<Uuid>,
        limit: Option<i64>,
    ) -> ImksResult<CursorPage<Message>> {
        let effective_limit = clamp_limit(limit);
        // Fetch one extra row to determine `has_more`.
        let fetch_limit = effective_limit + 1;

        let rows = match before {
            Some(cursor) => {
                sqlx::query_as::<_, Message>(
                    r#"
                    SELECT * FROM message
                    WHERE channel_id = $1
                      AND deleted_at IS NULL
                      AND id < $2
                    ORDER BY id DESC
                    LIMIT $3
                    "#,
                )
                .bind(channel_id)
                .bind(cursor)
                .bind(fetch_limit)
                .fetch_all(self.pool())
                .await?
            }
            None => {
                sqlx::query_as::<_, Message>(
                    r#"
                    SELECT * FROM message
                    WHERE channel_id = $1
                      AND deleted_at IS NULL
                    ORDER BY id DESC
                    LIMIT $2
                    "#,
                )
                .bind(channel_id)
                .bind(fetch_limit)
                .fetch_all(self.pool())
                .await?
            }
        };

        Ok(CursorPage::from_raw(rows, effective_limit, |m| m.id))
    }

    /// List messages in a thread with cursor-based pagination.
    pub async fn list_by_thread(
        &self,
        thread_id: Uuid,
        before: Option<Uuid>,
        limit: Option<i64>,
    ) -> ImksResult<CursorPage<Message>> {
        let effective_limit = clamp_limit(limit);
        let fetch_limit = effective_limit + 1;

        let rows = match before {
            Some(cursor) => {
                sqlx::query_as::<_, Message>(
                    r#"
                    SELECT * FROM message
                    WHERE thread_id = $1
                      AND deleted_at IS NULL
                      AND id < $2
                    ORDER BY id DESC
                    LIMIT $3
                    "#,
                )
                .bind(thread_id)
                .bind(cursor)
                .bind(fetch_limit)
                .fetch_all(self.pool())
                .await?
            }
            None => {
                sqlx::query_as::<_, Message>(
                    r#"
                    SELECT * FROM message
                    WHERE thread_id = $1
                      AND deleted_at IS NULL
                    ORDER BY id DESC
                    LIMIT $2
                    "#,
                )
                .bind(thread_id)
                .bind(fetch_limit)
                .fetch_all(self.pool())
                .await?
            }
        };

        Ok(CursorPage::from_raw(rows, effective_limit, |m| m.id))
    }

    /// Get message reaction counts grouped by emoji content.
    ///
    /// Returns `(content, count)` pairs for the given message.
    pub async fn get_reaction_counts(&self, message_id: Uuid) -> ImksResult<Vec<(String, i64)>> {
        let rows = sqlx::query(
            r#"
            SELECT content, COUNT(*)::BIGINT AS cnt
            FROM message_reaction
            WHERE message_id = $1
            GROUP BY content
            "#,
        )
        .bind(message_id)
        .fetch_all(self.pool())
        .await?;

        Ok(rows
            .into_iter()
            .map(|r| (r.get("content"), r.get("cnt")))
            .collect())
    }

    /// Count attachments and embeds for a message.
    pub async fn get_content_counts(&self, message_id: Uuid) -> ImksResult<(i64, i64)> {
        let att_row = sqlx::query(
            "SELECT COUNT(*)::BIGINT AS cnt FROM message_attachment WHERE message_id = $1",
        )
        .bind(message_id)
        .fetch_one(self.pool())
        .await?;

        let emb_row =
            sqlx::query("SELECT COUNT(*)::BIGINT AS cnt FROM message_embed WHERE message_id = $1")
                .bind(message_id)
                .fetch_one(self.pool())
                .await?;

        Ok((att_row.get("cnt"), emb_row.get("cnt")))
    }
}