//! Poll CRUD operations on `MessageRepo`.
//!
//! Handles poll creation (with options), voting (with denormalized counts),
//! and result retrieval.

use chrono::Utc;
use sqlx::Row;
use uuid::Uuid;

use crate::ImksResult;
use crate::models::message_poll::{MessagePoll, MessagePollOption, MessagePollVote, PollResult};

use super::message_repo::MessageRepo;

/// Canonical poll target resolved from the database.
#[derive(Debug, Clone, Copy)]
pub struct PollTarget {
    pub poll_id: Uuid,
    pub message_id: Uuid,
    pub channel_id: Uuid,
}

impl MessageRepo {
    /// Resolve and validate a poll option's canonical message/channel target.
    pub async fn get_poll_target(&self, poll_id: Uuid, option_id: Uuid) -> ImksResult<PollTarget> {
        let row = sqlx::query(
            r#"
            SELECT p.id AS poll_id, p.message_id, m.channel_id, o.id AS option_id
            FROM message_poll p
            JOIN message m ON m.id = p.message_id
            JOIN message_poll_option o ON o.poll_id = p.id AND o.id = $2
            WHERE p.id = $1 AND m.deleted_at IS NULL
            "#,
        )
        .bind(poll_id)
        .bind(option_id)
        .fetch_optional(self.pool())
        .await?
        .ok_or_else(|| crate::ImksError::NotFound(format!("poll {poll_id} option {option_id}")))?;

        Ok(PollTarget {
            poll_id: row.get("poll_id"),
            message_id: row.get("message_id"),
            channel_id: row.get("channel_id"),
        })
    }

    /// Create a poll with its options. Returns the poll (options fetched separately).
    pub async fn create_poll(
        &self,
        message_id: Uuid,
        question: &str,
        allow_multiselect: bool,
        max_selections: Option<i32>,
        expires_at: Option<chrono::DateTime<Utc>>,
        options: &[(String, Option<String>)],
    ) -> ImksResult<MessagePoll> {
        let poll_id = Uuid::now_v7();
        let now = Utc::now();

        let poll = sqlx::query_as::<_, MessagePoll>(
            r#"
            INSERT INTO message_poll (
                id, message_id, question, allow_multiselect,
                max_selections, expires_at, total_votes, created_at, updated_at
            ) VALUES ($1, $2, $3, $4, $5, $6, 0, $7, $7)
            RETURNING *
            "#,
        )
        .bind(poll_id)
        .bind(message_id)
        .bind(question)
        .bind(allow_multiselect)
        .bind(max_selections)
        .bind(expires_at)
        .bind(now)
        .fetch_one(self.pool())
        .await?;

        for (i, (text, emoji)) in options.iter().enumerate() {
            let opt_id = Uuid::now_v7();
            sqlx::query(
                r#"
                INSERT INTO message_poll_option (id, poll_id, text, emoji, vote_count, position)
                VALUES ($1, $2, $3, $4, 0, $5)
                "#,
            )
            .bind(opt_id)
            .bind(poll_id)
            .bind(text)
            .bind(emoji.as_deref())
            .bind(i as i32)
            .execute(self.pool())
            .await?;
        }

        Ok(poll)
    }

    /// Cast a validated vote and return the canonical message/channel target.
    pub async fn cast_vote_checked(
        &self,
        poll_id: Uuid,
        option_id: Uuid,
        user_id: Uuid,
    ) -> ImksResult<PollTarget> {
        let mut tx = self.pool().begin().await?;
        let now = Utc::now();

        let row = sqlx::query(
            r#"
            SELECT p.id AS poll_id, p.message_id, p.allow_multiselect, p.max_selections,
                   p.expires_at, m.channel_id, o.id AS option_id
            FROM message_poll p
            JOIN message m ON m.id = p.message_id
            JOIN message_poll_option o ON o.poll_id = p.id AND o.id = $2
            WHERE p.id = $1 AND m.deleted_at IS NULL
            FOR UPDATE OF p
            "#,
        )
        .bind(poll_id)
        .bind(option_id)
        .fetch_optional(&mut *tx)
        .await?
        .ok_or_else(|| crate::ImksError::NotFound(format!("poll {poll_id} option {option_id}")))?;

        let expires_at: Option<chrono::DateTime<Utc>> = row.get("expires_at");
        if expires_at.is_some_and(|exp| now >= exp) {
            return Err(crate::ImksError::InvalidInput("Poll has expired".into()));
        }

        let allow_multiselect: bool = row.get("allow_multiselect");
        let max_selections: Option<i32> = row.get("max_selections");
        let current_votes: Vec<Uuid> = sqlx::query_scalar(
            "SELECT option_id FROM message_poll_vote WHERE poll_id = $1 AND user_id = $2",
        )
        .bind(poll_id)
        .bind(user_id)
        .fetch_all(&mut *tx)
        .await?;

        if current_votes.contains(&option_id) {
            return Err(crate::ImksError::InvalidInput(
                "Already voted for this option".into(),
            ));
        }
        if !allow_multiselect && !current_votes.is_empty() {
            return Err(crate::ImksError::InvalidInput(
                "Poll allows only one selection".into(),
            ));
        }
        if let Some(max) = max_selections
            && current_votes.len() >= max.max(1) as usize
        {
            return Err(crate::ImksError::InvalidInput(
                "Poll selection limit exceeded".into(),
            ));
        }

        let vote_id = Uuid::now_v7();
        sqlx::query(
            r#"
            INSERT INTO message_poll_vote (id, poll_id, option_id, user_id, created_at)
            VALUES ($1, $2, $3, $4, $5)
            "#,
        )
        .bind(vote_id)
        .bind(poll_id)
        .bind(option_id)
        .bind(user_id)
        .bind(now)
        .execute(&mut *tx)
        .await?;

        sqlx::query("UPDATE message_poll_option SET vote_count = vote_count + 1 WHERE id = $1")
            .bind(option_id)
            .execute(&mut *tx)
            .await?;

        sqlx::query(
            "UPDATE message_poll SET total_votes = total_votes + 1, updated_at = $1 WHERE id = $2",
        )
        .bind(now)
        .bind(poll_id)
        .execute(&mut *tx)
        .await?;

        tx.commit().await?;
        Ok(PollTarget {
            poll_id,
            message_id: row.get("message_id"),
            channel_id: row.get("channel_id"),
        })
    }

    /// Remove a validated vote and return the canonical message/channel target.
    pub async fn remove_vote_checked(
        &self,
        poll_id: Uuid,
        option_id: Uuid,
        user_id: Uuid,
    ) -> ImksResult<Option<PollTarget>> {
        let mut tx = self.pool().begin().await?;
        let now = Utc::now();

        let row = sqlx::query(
            r#"
            SELECT p.id AS poll_id, p.message_id, m.channel_id, o.id AS option_id
            FROM message_poll p
            JOIN message m ON m.id = p.message_id
            JOIN message_poll_option o ON o.poll_id = p.id AND o.id = $2
            WHERE p.id = $1 AND m.deleted_at IS NULL
            FOR UPDATE OF p
            "#,
        )
        .bind(poll_id)
        .bind(option_id)
        .fetch_optional(&mut *tx)
        .await?
        .ok_or_else(|| crate::ImksError::NotFound(format!("poll {poll_id} option {option_id}")))?;

        let result = sqlx::query(
            r#"
            DELETE FROM message_poll_vote
            WHERE poll_id = $1 AND option_id = $2 AND user_id = $3
            "#,
        )
        .bind(poll_id)
        .bind(option_id)
        .bind(user_id)
        .execute(&mut *tx)
        .await?;

        if result.rows_affected() == 0 {
            tx.commit().await?;
            return Ok(None);
        }

        sqlx::query(
            "UPDATE message_poll_option SET vote_count = GREATEST(vote_count - 1, 0) WHERE id = $1",
        )
        .bind(option_id)
        .execute(&mut *tx)
        .await?;

        sqlx::query(
            "UPDATE message_poll SET total_votes = GREATEST(total_votes - 1, 0), updated_at = $1 WHERE id = $2",
        )
        .bind(now)
        .bind(poll_id)
        .execute(&mut *tx)
        .await?;

        tx.commit().await?;
        Ok(Some(PollTarget {
            poll_id,
            message_id: row.get("message_id"),
            channel_id: row.get("channel_id"),
        }))
    }

    /// Cast a vote. Increments denormalized counts atomically.
    pub async fn vote(
        &self,
        poll_id: Uuid,
        option_id: Uuid,
        user_id: Uuid,
    ) -> ImksResult<MessagePollVote> {
        let id = Uuid::now_v7();
        let now = Utc::now();

        let vote = sqlx::query_as::<_, MessagePollVote>(
            r#"
            INSERT INTO message_poll_vote (id, poll_id, option_id, user_id, created_at)
            VALUES ($1, $2, $3, $4, $5)
            ON CONFLICT (poll_id, user_id, option_id) DO NOTHING
            RETURNING *
            "#,
        )
        .bind(id)
        .bind(poll_id)
        .bind(option_id)
        .bind(user_id)
        .bind(now)
        .fetch_optional(self.pool())
        .await?
        .ok_or_else(|| crate::ImksError::InvalidInput("Already voted for this option".into()))?;

        sqlx::query("UPDATE message_poll_option SET vote_count = vote_count + 1 WHERE id = $1")
            .bind(option_id)
            .execute(self.pool())
            .await?;

        sqlx::query(
            "UPDATE message_poll SET total_votes = total_votes + 1, updated_at = $1 WHERE id = $2",
        )
        .bind(now)
        .bind(poll_id)
        .execute(self.pool())
        .await?;

        Ok(vote)
    }

    /// Remove a vote. Decrements denormalized counts.
    pub async fn remove_vote(
        &self,
        poll_id: Uuid,
        option_id: Uuid,
        user_id: Uuid,
    ) -> ImksResult<bool> {
        let result = sqlx::query(
            r#"
            DELETE FROM message_poll_vote
            WHERE poll_id = $1 AND option_id = $2 AND user_id = $3
            "#,
        )
        .bind(poll_id)
        .bind(option_id)
        .bind(user_id)
        .execute(self.pool())
        .await?;

        if result.rows_affected() == 0 {
            return Ok(false);
        }

        sqlx::query(
            "UPDATE message_poll_option SET vote_count = GREATEST(vote_count - 1, 0) WHERE id = $1",
        )
        .bind(option_id)
        .execute(self.pool())
        .await?;

        sqlx::query(
            "UPDATE message_poll SET total_votes = GREATEST(total_votes - 1, 0), updated_at = $1 WHERE id = $2",
        )
        .bind(Utc::now())
        .bind(poll_id)
        .execute(self.pool())
        .await?;

        Ok(true)
    }

    /// Get full poll results including options, vote counts, and the given user's votes.
    pub async fn get_poll_result(
        &self,
        message_id: Uuid,
        user_id: Uuid,
    ) -> ImksResult<Option<PollResult>> {
        let poll =
            sqlx::query_as::<_, MessagePoll>("SELECT * FROM message_poll WHERE message_id = $1")
                .bind(message_id)
                .fetch_optional(self.pool())
                .await?;

        let Some(poll) = poll else {
            return Ok(None);
        };

        let options: Vec<MessagePollOption> = sqlx::query_as(
            "SELECT * FROM message_poll_option WHERE poll_id = $1 ORDER BY position",
        )
        .bind(poll.id)
        .fetch_all(self.pool())
        .await?;

        let my_votes: Vec<Uuid> = sqlx::query_scalar(
            "SELECT option_id FROM message_poll_vote WHERE poll_id = $1 AND user_id = $2",
        )
        .bind(poll.id)
        .bind(user_id)
        .fetch_all(self.pool())
        .await?;

        Ok(Some(PollResult::from_poll(poll, options, my_votes)))
    }

    /// Close a poll by setting its expiration to now.
    pub async fn close_poll(&self, message_id: Uuid) -> ImksResult<()> {
        let now = Utc::now();
        sqlx::query(
            r#"
            UPDATE message_poll
            SET expires_at = $1, updated_at = $1
            WHERE message_id = $2 AND (expires_at IS NULL OR expires_at > $1)
            "#,
        )
        .bind(now)
        .bind(message_id)
        .execute(self.pool())
        .await?;
        Ok(())
    }
}