use std::collections::HashMap;
use std::path::{Path, PathBuf};

use tantivy::collector::TopDocs;
use tantivy::query::{
    BooleanQuery, BoostQuery, FuzzyTermQuery, Occur, Query, QueryParser, TermQuery,
};
use tantivy::schema::{IndexRecordOption, Value};
use tantivy::{Index, TantivyDocument, Term};
use tonic::{Request, Response, Status};

use common::proto::komp_ac::search::searcher_server::Searcher;
use common::proto::komp_ac::search::{search_response::Hit, SearchRequest, SearchResponse};
pub use common::proto::komp_ac::search::searcher_server::SearcherServer;
use common::search::{register_slovak_tokenizers, search_index_path};
use sqlx::{PgPool, Row};
use tracing::info;

const INDEX_ROOT: &str = "./tantivy_indexes";
const DEFAULT_RESULT_LIMIT: usize = 5;
const SEARCH_RESULT_LIMIT: usize = 100;

pub struct SearcherService {
    pub pool: PgPool,
}

struct SearchTarget {
    table_name: String,
    qualified_table: String,
    index_path: PathBuf,
}

fn normalize_slovak_text(text: &str) -> String {
    text.chars()
        .map(|c| match c {
            'á' | 'à' | 'â' | 'ä' | 'ă' | 'ā' => 'a',
            'Á' | 'À' | 'Â' | 'Ä' | 'Ă' | 'Ā' => 'A',
            'é' | 'è' | 'ê' | 'ë' | 'ě' | 'ē' => 'e',
            'É' | 'È' | 'Ê' | 'Ë' | 'Ě' | 'Ē' => 'E',
            'í' | 'ì' | 'î' | 'ï' | 'ī' => 'i',
            'Í' | 'Ì' | 'Î' | 'Ï' | 'Ī' => 'I',
            'ó' | 'ò' | 'ô' | 'ö' | 'ō' | 'ő' => 'o',
            'Ó' | 'Ò' | 'Ô' | 'Ö' | 'Ō' | 'Ő' => 'O',
            'ú' | 'ù' | 'û' | 'ü' | 'ū' | 'ű' => 'u',
            'Ú' | 'Ù' | 'Û' | 'Ü' | 'Ū' | 'Ű' => 'U',
            'ý' | 'ỳ' | 'ŷ' | 'ÿ' => 'y',
            'Ý' | 'Ỳ' | 'Ŷ' | 'Ÿ' => 'Y',
            'č' => 'c',
            'Č' => 'C',
            'ď' => 'd',
            'Ď' => 'D',
            'ľ' => 'l',
            'Ľ' => 'L',
            'ň' => 'n',
            'Ň' => 'N',
            'ř' => 'r',
            'Ř' => 'R',
            'š' => 's',
            'Š' => 'S',
            'ť' => 't',
            'Ť' => 'T',
            'ž' => 'z',
            'Ž' => 'Z',
            _ => c,
        })
        .collect()
}

fn validate_identifier(value: &str, field_name: &str) -> Result<(), Status> {
    let mut chars = value.chars();
    let Some(first) = chars.next() else {
        return Err(Status::invalid_argument(format!(
            "{field_name} must not be empty"
        )));
    };

    if !(first.is_ascii_alphabetic() || first == '_')
        || !chars.all(|ch| ch.is_ascii_alphanumeric() || ch == '_')
    {
        return Err(Status::invalid_argument(format!(
            "{field_name} contains invalid characters"
        )));
    }

    Ok(())
}

fn qualify_profile_table(profile_name: &str, table_name: &str) -> String {
    format!("\"{}\".\"{}\"", profile_name, table_name)
}

async fn profile_exists(pool: &PgPool, profile_name: &str) -> Result<bool, Status> {
    let exists = sqlx::query_scalar::<_, bool>("SELECT EXISTS(SELECT 1 FROM schemas WHERE name = $1)")
        .bind(profile_name)
        .fetch_one(pool)
        .await
        .map_err(|e| Status::internal(format!("Profile lookup failed: {}", e)))?;
    Ok(exists)
}

// Scope resolution
async fn resolve_search_targets(
    pool: &PgPool,
    profile_name: &str,
    requested_table: Option<&str>,
) -> Result<Vec<SearchTarget>, Status> {
    validate_identifier(profile_name, "profile_name")?;

    if !profile_exists(pool, profile_name).await? {
        return Err(Status::not_found(format!(
            "Profile '{}' was not found",
            profile_name
        )));
    }

    let tables = if let Some(table_name) = requested_table.filter(|value| !value.trim().is_empty()) {
        validate_identifier(table_name, "table_name")?;

        let row = sqlx::query_scalar::<_, String>(
            r#"
            SELECT td.table_name
            FROM table_definitions td
            JOIN schemas s ON td.schema_id = s.id
            WHERE s.name = $1 AND td.table_name = $2
            "#,
        )
        .bind(profile_name)
        .bind(table_name)
        .fetch_optional(pool)
        .await
        .map_err(|e| Status::internal(format!("Table lookup failed: {}", e)))?;

        let table_name = row.ok_or_else(|| {
            Status::not_found(format!(
                "Table '{}' was not found in profile '{}'",
                table_name, profile_name
            ))
        })?;

        vec![table_name]
    } else {
        sqlx::query_scalar::<_, String>(
            r#"
            SELECT td.table_name
            FROM table_definitions td
            JOIN schemas s ON td.schema_id = s.id
            WHERE s.name = $1
            ORDER BY td.table_name
            "#,
        )
        .bind(profile_name)
        .fetch_all(pool)
        .await
        .map_err(|e| Status::internal(format!("Profile table lookup failed: {}", e)))?
    };

    Ok(tables
        .into_iter()
        .map(|table_name| SearchTarget {
            qualified_table: qualify_profile_table(profile_name, &table_name),
            index_path: search_index_path(Path::new(INDEX_ROOT), profile_name, &table_name),
            table_name,
        })
        .collect())
}

// Query building
fn build_query(index: &Index, normalized_query: &str) -> Result<Option<BooleanQuery>, Status> {
    let schema = index.schema();
    let prefix_edge_field = schema
        .get_field("prefix_edge")
        .map_err(|_| Status::internal("Schema is missing the 'prefix_edge' field."))?;
    let prefix_full_field = schema
        .get_field("prefix_full")
        .map_err(|_| Status::internal("Schema is missing the 'prefix_full' field."))?;
    let text_ngram_field = schema
        .get_field("text_ngram")
        .map_err(|_| Status::internal("Schema is missing the 'text_ngram' field."))?;

    let words: Vec<&str> = normalized_query.split_whitespace().collect();
    if words.is_empty() {
        return Ok(None);
    }

    let mut query_layers: Vec<(Occur, Box<dyn Query>)> = Vec::new();

    // Layer 1: prefix
    {
        let mut must_clauses: Vec<(Occur, Box<dyn Query>)> = Vec::new();
        for word in &words {
            let edge_term = Term::from_field_text(prefix_edge_field, word);
            let full_term = Term::from_field_text(prefix_full_field, word);

            let per_word_query = BooleanQuery::new(vec![
                (
                    Occur::Should,
                    Box::new(TermQuery::new(edge_term, IndexRecordOption::Basic)),
                ),
                (
                    Occur::Should,
                    Box::new(TermQuery::new(full_term, IndexRecordOption::Basic)),
                ),
            ]);
            must_clauses.push((Occur::Must, Box::new(per_word_query)));
        }

        if !must_clauses.is_empty() {
            let prefix_query = BooleanQuery::new(must_clauses);
            let boosted_query = BoostQuery::new(Box::new(prefix_query), 4.0);
            query_layers.push((Occur::Should, Box::new(boosted_query)));
        }
    }

    // Layer 2: fuzzy
    {
        let last_word = words
            .last()
            .ok_or_else(|| Status::internal("Query normalization lost all tokens"))?;
        let fuzzy_term = Term::from_field_text(prefix_full_field, last_word);
        let fuzzy_query = FuzzyTermQuery::new(fuzzy_term, 2, true);
        let boosted_query = BoostQuery::new(Box::new(fuzzy_query), 3.0);
        query_layers.push((Occur::Should, Box::new(boosted_query)));
    }

    // Layer 3: phrase
    if words.len() > 1 {
        let slop_parser = QueryParser::for_index(index, vec![prefix_full_field]);
        let slop_query_str = format!("\"{}\"~3", normalized_query);
        if let Ok(slop_query) = slop_parser.parse_query(&slop_query_str) {
            let boosted_query = BoostQuery::new(slop_query, 2.0);
            query_layers.push((Occur::Should, Box::new(boosted_query)));
        }
    }

    // Layer 4: ngram
    {
        let ngram_parser = QueryParser::for_index(index, vec![text_ngram_field]);
        if let Ok(ngram_query) = ngram_parser.parse_query(normalized_query) {
            let boosted_query = BoostQuery::new(ngram_query, 1.0);
            query_layers.push((Occur::Should, Box::new(boosted_query)));
        }
    }

    Ok(Some(BooleanQuery::new(query_layers)))
}

// Empty query
async fn fetch_default_hits(pool: &PgPool, target: &SearchTarget) -> Result<Vec<Hit>, Status> {
    let sql = format!(
        "SELECT id, to_jsonb(t) AS data FROM {} t WHERE deleted = FALSE ORDER BY id DESC LIMIT {}",
        target.qualified_table, DEFAULT_RESULT_LIMIT
    );

    let rows = sqlx::query(&sql)
        .fetch_all(pool)
        .await
        .map_err(|e| Status::internal(format!("DB query for default results failed: {}", e)))?;

    Ok(rows
        .into_iter()
        .map(|row| {
            let id: i64 = row.try_get("id").unwrap_or_default();
            let json_data: serde_json::Value = row.try_get("data").unwrap_or_default();
            Hit {
                id,
                score: 0.0,
                content_json: json_data.to_string(),
                table_name: target.table_name.clone(),
            }
        })
        .collect())
}

// Search + hydrate
async fn search_target(
    pool: &PgPool,
    target: &SearchTarget,
    query_str: &str,
) -> Result<Vec<Hit>, Status> {
    if !target.index_path.exists() {
        return Ok(vec![]);
    }

    let index = Index::open_in_dir(&target.index_path)
        .map_err(|e| Status::internal(format!("Failed to open index: {}", e)))?;
    register_slovak_tokenizers(&index)
        .map_err(|e| Status::internal(format!("Failed to register Slovak tokenizers: {}", e)))?;

    let Some(master_query) = build_query(&index, &normalize_slovak_text(query_str))? else {
        return Ok(vec![]);
    };

    let reader = index
        .reader()
        .map_err(|e| Status::internal(format!("Failed to create index reader: {}", e)))?;
    let searcher = reader.searcher();
    let schema = index.schema();
    let pg_id_field = schema
        .get_field("pg_id")
        .map_err(|_| Status::internal("Schema is missing the 'pg_id' field."))?;

    let top_docs = searcher
        .search(&master_query, &TopDocs::with_limit(SEARCH_RESULT_LIMIT))
        .map_err(|e| Status::internal(format!("Search failed: {}", e)))?;

    if top_docs.is_empty() {
        return Ok(vec![]);
    }

    let mut scored_ids: Vec<(f32, u64)> = Vec::new();
    for (score, doc_address) in top_docs {
        let doc: TantivyDocument = searcher
            .doc(doc_address)
            .map_err(|e| Status::internal(format!("Failed to retrieve document: {}", e)))?;
        if let Some(pg_id_value) = doc.get_first(pg_id_field) {
            if let Some(pg_id) = pg_id_value.as_u64() {
                scored_ids.push((score, pg_id));
            }
        }
    }

    if scored_ids.is_empty() {
        return Ok(vec![]);
    }

    let pg_ids: Vec<i64> = scored_ids.iter().map(|(_, id)| *id as i64).collect();
    let sql = format!(
        "SELECT id, to_jsonb(t) AS data FROM {} t WHERE deleted = FALSE AND id = ANY($1)",
        target.qualified_table
    );

    let rows = sqlx::query(&sql)
        .bind(&pg_ids)
        .fetch_all(pool)
        .await
        .map_err(|e| Status::internal(format!("Database query failed: {}", e)))?;

    let mut content_map: HashMap<i64, String> = HashMap::new();
    for row in rows {
        let id: i64 = row.try_get("id").unwrap_or_default();
        let json_data: serde_json::Value = row.try_get("data").unwrap_or_default();
        content_map.insert(id, json_data.to_string());
    }

    Ok(scored_ids
        .into_iter()
        .filter_map(|(score, pg_id)| {
            content_map.get(&(pg_id as i64)).map(|content_json| Hit {
                id: pg_id as i64,
                score,
                content_json: content_json.clone(),
                table_name: target.table_name.clone(),
            })
        })
        .collect())
}

#[tonic::async_trait]
impl Searcher for SearcherService {
    async fn search_table(
        &self,
        request: Request<SearchRequest>,
    ) -> Result<Response<SearchResponse>, Status> {
        let req = request.into_inner();
        let profile_name = req.profile_name.trim();
        if profile_name.is_empty() {
            return Err(Status::invalid_argument("profile_name is required"));
        }

        // Request scope
        let requested_table = req.table_name.as_deref().map(str::trim);
        let targets = resolve_search_targets(&self.pool, profile_name, requested_table).await?;

        if targets.is_empty() {
            return Ok(Response::new(SearchResponse { hits: vec![] }));
        }

        let query = req.query.trim();
        if query.is_empty() {
            // Empty query
            if targets.len() != 1 {
                return Err(Status::invalid_argument(
                    "table_name is required when query is empty",
                ));
            }

            let hits = fetch_default_hits(&self.pool, &targets[0]).await?;
            info!(
                "Empty query for profile '{}' table '{}'. Returning {} default hits.",
                profile_name,
                targets[0].table_name,
                hits.len()
            );
            return Ok(Response::new(SearchResponse { hits }));
        }

        if requested_table.is_some() && targets.len() == 1 && !targets[0].index_path.exists() {
            return Err(Status::not_found(format!(
                "No search index found for table '{}'",
                targets[0].table_name
            )));
        }

        // Merge per-table hits
        let mut hits = Vec::new();
        for target in &targets {
            hits.extend(search_target(&self.pool, target, query).await?);
        }

        hits.sort_by(|left, right| right.score.total_cmp(&left.score));
        if hits.len() > SEARCH_RESULT_LIMIT {
            hits.truncate(SEARCH_RESULT_LIMIT);
        }

        info!(
            "Processed search for profile '{}' (table scope: {}). Returning {} hits.",
            profile_name,
            requested_table.unwrap_or("*"),
            hits.len()
        );

        Ok(Response::new(SearchResponse { hits }))
    }
}