use async_trait::async_trait;
use atuin_client::{
    database::{Database, DbSearchMode, OptFilters},
    history::{AUTHOR_FILTER_ALL_USER, History},
    settings::Settings,
};
use atuin_daemon::client::{DaemonClientErrorKind, SearchClient, SearchParams, classify_error};
use atuin_nucleo_matcher::{
    Config, Matcher, Utf32Str,
    pattern::{CaseMatching, Normalization, Pattern},
};
use eyre::Result;
use tracing::{Level, debug, instrument, span};
use uuid::Uuid;

use super::{SearchEngine, SearchState};
use crate::command::client::daemon;

pub struct Search {
    client: Option<SearchClient>,
    query_id: u64,
    settings: Settings,
    #[cfg(unix)]
    socket_path: String,
    #[cfg(not(unix))]
    tcp_port: u64,
}

impl Search {
    pub fn new(settings: &Settings) -> Self {
        Search {
            client: None,
            query_id: 0,
            settings: settings.clone(),
            #[cfg(unix)]
            socket_path: settings.daemon.socket_path.clone(),
            #[cfg(not(unix))]
            tcp_port: settings.daemon.tcp_port,
        }
    }

    #[instrument(skip_all, level = Level::TRACE, name = "get_daemon_client")]
    async fn get_client(&mut self) -> Result<&mut SearchClient> {
        if self.client.is_none() {
            self.connect().await?;
        }
        Ok(self.client.as_mut().unwrap())
    }

    async fn connect(&mut self) -> Result<()> {
        #[cfg(unix)]
        let client = SearchClient::new(self.socket_path.clone()).await?;

        #[cfg(not(unix))]
        let client = SearchClient::new(self.tcp_port).await?;

        self.client = Some(client);
        Ok(())
    }

    fn should_retry(err: &eyre::Report) -> bool {
        matches!(
            classify_error(err),
            DaemonClientErrorKind::Connect
                | DaemonClientErrorKind::Unavailable
                | DaemonClientErrorKind::Unimplemented
        )
    }

    fn next_query_id(&mut self) -> u64 {
        self.query_id += 1;
        self.query_id
    }

    /// Check if query contains regex pattern (r/.../)
    /// Nucleo doesn't support regex, so we fall back to database search
    fn contains_regex_pattern(query: &str) -> bool {
        query.starts_with("r/") || query.contains(" r/")
    }

    #[instrument(skip_all, level = Level::TRACE, name = "daemon_db_fallback")]
    async fn fallback_to_db_search(
        &self,
        state: &SearchState,
        db: &dyn Database,
    ) -> Result<Vec<History>> {
        let results = db
            .search(
                DbSearchMode::FullText,
                state.filter_mode,
                &state.context,
                state.input.as_str(),
                OptFilters {
                    limit: Some(200),
                    authors: &[AUTHOR_FILTER_ALL_USER.to_owned()],
                    shells: state.shells.to_list().as_slice(),
                    ..Default::default()
                },
            )
            .await
            .map_or(Vec::new(), |r| r.into_iter().collect());
        Ok(results)
    }

    #[instrument(skip_all, level = Level::TRACE, name = "hydrate_from_db", fields(count = ids.len()))]
    async fn hydrate_from_db(&self, db: &dyn Database, ids: &[String]) -> Result<Vec<History>> {
        let placeholders: Vec<String> = ids.iter().map(|id| format!("'{id}'")).collect();
        let sql_query = format!(
            "SELECT * FROM history WHERE id IN ({}) ORDER BY timestamp DESC",
            placeholders.join(",")
        );
        Ok(db.query_history(&sql_query).await?)
    }
}

#[async_trait]
impl SearchEngine for Search {
    #[instrument(skip_all, level = Level::TRACE, name = "daemon_search", fields(query = %state.input.as_str()))]
    async fn full_query(
        &mut self,
        state: &SearchState,
        db: &mut dyn Database,
    ) -> Result<Vec<History>> {
        let query = state.input.as_str().to_string();

        // Fall back to database for regex queries (Nucleo doesn't support regex)
        if Self::contains_regex_pattern(&query) {
            debug!(query = %query, "[daemon-client] regex detected, falling back to db");
            return self.fallback_to_db_search(state, db).await;
        }

        let query_id = self.next_query_id();

        let span =
            span!(Level::TRACE, "daemon_search.req_resp", query = %query, query_id = query_id);

        let params = || SearchParams {
            query: query.clone(),
            query_id,
            filter_mode: state.filter_mode,
            context: Some(state.context.clone()),
            shells: state.shells.to_list().to_vec(),
        };

        // Try to connect and search; if it fails with a retriable error,
        // auto-start the daemon and retry once.
        let first_attempt = async {
            let client = self.get_client().await?;
            client.search(params()).await
        }
        .await;

        let mut stream = match first_attempt {
            Ok(stream) => stream,
            Err(err) if self.settings.daemon.autostart && Self::should_retry(&err) => {
                debug!("daemon not available, attempting auto-start");
                self.client = None;

                daemon::ensure_daemon_running(&self.settings).await?;

                let client = self.get_client().await?;
                client.search(params()).await?
            }
            Err(err) => return Err(err),
        };

        let mut ids = Vec::with_capacity(200);
        span!(Level::TRACE, "daemon_search.resp")
            .in_scope(async || {
                while let Ok(Some(response)) = stream.message().await {
                    let span2 = span!(
                        Level::TRACE,
                        "daemon_search.resp.item",
                        query_id = response.query_id
                    );
                    let _span2 = span2.enter();
                    // Only process if the query_id matches (prevents stale responses)
                    if response.query_id == query_id {
                        let uuids = response
                            .ids
                            .iter()
                            .map(|id| {
                                let bytes: [u8; 16] =
                                    id.as_slice().try_into().expect("id should be 16 bytes");
                                Uuid::from_bytes(bytes).as_simple().to_string()
                            })
                            .collect::<Vec<_>>();
                        ids.extend(uuids);
                    }
                    drop(_span2);
                    drop(span2);
                }
            })
            .await;
        drop(span);

        if ids.is_empty() {
            debug!(query = %query, results = 0, "[daemon-client] empty results");
            return Ok(Vec::new());
        }

        // // Hydrate from local database
        let results = self.hydrate_from_db(db, &ids).await?;

        // // Reorder results to match the order from the daemon (which is ranked by relevance)
        let ordered_results = span!(Level::TRACE, "reorder_results").in_scope(|| {
            let mut ordered_results = Vec::with_capacity(results.len());
            for id in &ids {
                if let Some(history) = results.iter().find(|h| h.id.0 == *id) {
                    ordered_results.push(history.clone());
                }
            }
            ordered_results
        });

        debug!(
            query = %query,
            results = results.len(),
            "[daemon-client]"
        );

        Ok(ordered_results)
    }

    #[instrument(skip_all, level = Level::TRACE, name = "daemon_highlight")]
    fn get_highlight_indices(&self, command: &str, search_input: &str) -> Vec<usize> {
        // Use fulltext highlighting for regex queries
        if Self::contains_regex_pattern(search_input) {
            return super::db::get_highlight_indices_fulltext(command, search_input);
        }

        let mut matcher = Matcher::new(Config::DEFAULT);
        let pattern = Pattern::parse(search_input, CaseMatching::Smart, Normalization::Smart);

        let mut indices: Vec<u32> = Vec::new();
        let mut haystack_buf = Vec::new();

        let haystack = Utf32Str::new(command, &mut haystack_buf);
        pattern.indices(haystack, &mut matcher, &mut indices);

        // Convert u32 indices to usize
        indices.into_iter().map(|i| i as usize).collect()
    }
}
