use std::sync::Arc;

use axum::extract::{Query, State};
use axum::response::Json;
use serde::{Deserialize, Serialize};
use tracing::info;

use crate::api_error::ApiError;
use crate::consts::MAX_POIS_PER_REQUEST;
use crate::data::{resolve_poi_category_filter, POICategoryGroup, SchoolMetadata};
use crate::parsing::require_bounds;
use crate::state::SharedState;

#[derive(Serialize)]
#[allow(clippy::upper_case_acronyms)]
pub struct POI {
    id: String,
    name: String,
    category: String,
    icon_category: String,
    group: String,
    lat: f32,
    lng: f32,
    emoji: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    school: Option<SchoolMetadata>,
}

#[derive(Serialize)]
pub struct POIsResponse {
    pois: Vec<POI>,
}

#[derive(Deserialize)]
pub struct POIParams {
    bounds: Option<String>,
    /// Comma-separated list of categories to filter by
    categories: Option<String>,
}

pub async fn get_pois(
    State(shared): State<Arc<SharedState>>,
    Query(params): Query<POIParams>,
) -> Result<Json<POIsResponse>, ApiError> {
    let state = shared.load_state();
    let (south, west, north, east) = require_bounds(params.bounds).map_err(ApiError::from)?;

    let category_filter: Option<rustc_hash::FxHashSet<u16>> = params
        .categories
        .as_deref()
        .filter(|text| !text.is_empty())
        .map(|text| resolve_poi_category_filter(&state.poi_data.category.values, text));
    let categories_raw = params.categories;

    let num_categories = category_filter.as_ref().map(|cats| cats.len()).unwrap_or(0);

    let pois = tokio::task::spawn_blocking(move || {
        let t0 = std::time::Instant::now();
        let row_indices = state.poi_grid.query(south, west, north, east);

        let matching_rows: Vec<usize> = row_indices
            .iter()
            .filter_map(|&row_idx| {
                let row = row_idx as usize;
                if let Some(ref categories) = category_filter {
                    if !categories.contains(&state.poi_data.category.indices[row]) {
                        return None;
                    }
                }
                Some(row)
            })
            .collect();

        let mut matching_pois = matching_rows;

        if matching_pois.len() > MAX_POIS_PER_REQUEST {
            let ratio = (matching_pois.len() / MAX_POIS_PER_REQUEST) as u32;
            let step = ratio.next_power_of_two();
            let mask = step - 1;
            matching_pois.retain(|&row| state.poi_data.priority[row] & mask == 0);
            if matching_pois.len() > MAX_POIS_PER_REQUEST {
                matching_pois.sort_unstable_by_key(|&row| state.poi_data.priority[row]);
                matching_pois.truncate(MAX_POIS_PER_REQUEST);
            }
        }

        let pois: Vec<POI> = matching_pois
            .iter()
            .map(|&row| POI {
                id: state.poi_data.id(row).to_string(),
                name: state.poi_data.name[row].clone(),
                category: state.poi_data.category.get(row).to_string(),
                icon_category: state.poi_data.icon_category.get(row).to_string(),
                group: state.poi_data.group.get(row).to_string(),
                lat: state.poi_data.lat[row],
                lng: state.poi_data.lng[row],
                emoji: state.poi_data.emoji.get(row).to_string(),
                school: state.poi_data.school(row).cloned(),
            })
            .collect();

        let elapsed = t0.elapsed();
        info!(
            results = pois.len(),
            candidates = row_indices.len(),
            categories = num_categories,
            categories_raw = categories_raw.as_deref().unwrap_or("-"),
            ms = format_args!("{:.1}", elapsed.as_secs_f64() * 1000.0),
            "GET /api/pois"
        );

        pois
    })
    .await
    .map_err(|error| ApiError::Internal(error.to_string()))?;

    Ok(Json(POIsResponse { pois }))
}

#[derive(Serialize)]
pub struct POICategoriesResponse {
    groups: Vec<POICategoryGroup>,
}

pub async fn get_poi_categories(
    State(shared): State<Arc<SharedState>>,
) -> Json<POICategoriesResponse> {
    let state = shared.load_state();
    let groups: Vec<POICategoryGroup> = state.poi_category_groups.to_vec();

    let total: usize = groups.iter().map(|group| group.categories.len()).sum();
    info!(
        count = total,
        groups = groups.len(),
        "GET /api/poi-categories"
    );

    Json(POICategoriesResponse { groups })
}