//! What the IMAP sync loop reads to decide what to fetch: existence checks by
//! message-id and sender, the message-id lookup, and the folder/label sets.

use std::collections::HashSet;

use goingson_core::{CoreError, Email, Result, UserId};
use rusqlite::{Connection, params, params_from_iter};

use crate::utils::{bind_placeholders, query_all, query_opt};

use super::row::{EMAIL_SELECT_COLUMNS, EmailRow};

/// Whether an email with this message-id is already stored.
pub(super) fn exists_by_message_id(
    conn: &Connection,
    user_id: UserId,
    message_id: &str,
) -> Result<bool> {
    let count: i64 = conn
        .query_row(
            "SELECT COUNT(*) FROM emails WHERE user_id = ? AND message_id = ?",
            params![user_id.to_string(), message_id],
            |row| row.get(0),
        )
        .map_err(CoreError::database)?;
    Ok(count > 0)
}

/// Which of the given message-ids are already stored.
pub(super) fn exists_by_message_ids(
    conn: &Connection,
    user_id: UserId,
    message_ids: &[&str],
) -> Result<HashSet<String>> {
    if message_ids.is_empty() {
        return Ok(HashSet::new());
    }

    let placeholders = bind_placeholders(message_ids.len());
    let query = format!(
        "SELECT message_id FROM emails WHERE user_id = ? AND message_id IN ({placeholders})"
    );

    // user_id binds first, then one placeholder per message id.
    let mut binds: Vec<String> = vec![user_id.to_string()];
    binds.extend(message_ids.iter().map(|m| (*m).to_string()));

    let rows: Vec<String> = query_all(conn, &query, params_from_iter(binds.iter()), |row| {
        row.get(0)
    })?;

    Ok(rows.into_iter().collect())
}

/// Which of the given addresses have ever sent the user an email.
pub(super) fn exists_as_senders(
    conn: &Connection,
    user_id: UserId,
    addresses: &[&str],
) -> Result<HashSet<String>> {
    if addresses.is_empty() {
        return Ok(HashSet::new());
    }

    let placeholders = bind_placeholders(addresses.len());
    let query = format!(
        "SELECT DISTINCT LOWER(from_address) FROM emails WHERE user_id = ? AND LOWER(from_address) IN ({placeholders})"
    );

    let mut binds: Vec<String> = Vec::with_capacity(addresses.len() + 1);
    binds.push(user_id.to_string());
    binds.extend(addresses.iter().map(|a| a.to_lowercase()));

    let rows: Vec<String> = query_all(conn, &query, params_from_iter(binds), |row| row.get(0))?;

    Ok(rows.into_iter().collect())
}

/// One email by its RFC message-id.
pub(super) fn get_by_message_id(
    conn: &Connection,
    user_id: UserId,
    message_id: &str,
) -> Result<Option<Email>> {
    let query = format!(
        "SELECT {EMAIL_SELECT_COLUMNS} FROM emails e LEFT JOIN projects p ON e.project_id = p.id AND p.user_id = ? WHERE e.user_id = ? AND e.message_id = ?"
    );
    let row = query_opt(
        conn,
        &query,
        params![user_id.to_string(), user_id.to_string(), message_id],
        EmailRow::from_row,
    )?;
    row.map(Email::try_from).transpose()
}

/// Distinct IMAP source folders seen across the user's non-draft emails.
pub(super) fn list_folders(conn: &Connection, user_id: UserId) -> Result<Vec<String>> {
    query_all(
        conn,
        "SELECT DISTINCT source_folder FROM emails WHERE user_id = ? AND source_folder IS NOT NULL AND is_draft = 0 ORDER BY source_folder ASC",
        params![user_id.to_string()],
        |row| row.get(0),
    )
}

/// Distinct labels across the user's non-draft emails.
pub(super) fn list_labels(conn: &Connection, user_id: UserId) -> Result<Vec<String>> {
    // Extract all unique labels across all emails via JSON parsing
    query_all(
        conn,
        "SELECT DISTINCT j.value FROM emails e, json_each(e.labels) j WHERE e.user_id = ? AND e.is_draft = 0 ORDER BY j.value ASC",
        params![user_id.to_string()],
        |row| row.get(0),
    )
}