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//! Service layer for plant layer.

use std::io::Cursor;

use actix_http::StatusCode;
use actix_web::web::Data;
use chrono::Utc;
use image::{ImageBuffer, Rgba};

use crate::{
    config::data::AppDataInner,
    error::ServiceError,
    model::{
        dto::{HeatMapQueryParams, RelationSearchParameters, RelationsDto},
        entity::plant_layer,
    },
};

/// Generates a heatmap signaling ideal locations for planting the plant.
/// The return values are raw bytes of an PNG image.
///
/// # Errors
/// * If the connection to the database could not be established.
/// * If no map with id `map_id` exists.
/// * If no layer with id `layer_id` exists, if the layer is not a plant layer or if the layer is not part of the map.
/// * If no plant with id `plant_id` exists.
/// * If the image could not be parsed to bytes.
pub async fn heatmap(
    map_id: i32,
    query_params: HeatMapQueryParams,
    app_data: &Data<AppDataInner>,
) -> Result<Vec<u8>, ServiceError> {
    let mut conn = app_data.pool.get().await?;
    let result = plant_layer::heatmap(
        map_id,
        query_params.plant_layer_id,
        query_params.shade_layer_id,
        query_params.plant_id,
        query_params.date.unwrap_or_else(|| Utc::now().date_naive()),
        &mut conn,
    )
    .await?;

    let buffer = matrix_to_image(&result)?;

    Ok(buffer)
}

/// Parses the matrix of scores with values 0-1 to raw bytes of a PNG image.
#[allow(
    clippy::cast_possible_truncation,   // ok, because size of matrix shouldn't ever be larger than u32 and casting to u8 in image should remove floating point values
    clippy::indexing_slicing,           // ok, because size of image is generated using matrix width and height
    clippy::cast_sign_loss              // ok, because we only care about positive values
)]
fn matrix_to_image(matrix: &Vec<Vec<(f32, f32)>>) -> Result<Vec<u8>, ServiceError> {
    let (width, height) = (matrix[0].len(), matrix.len());
    let mut imgbuf = ImageBuffer::new(width as u32, height as u32);

    for (x, y, pixel) in imgbuf.enumerate_pixels_mut() {
        let (preference, relevance) = matrix[y as usize][x as usize];

        // The closer data is to 1 the greener it gets.
        let red = preference.mul_add(-255.0, 255.0);
        let green = preference * 255.0;
        let blue = 0.0_f32;
        // For some reason every relevance value returned by the database is between
        // (about) 0.5 and 1 while it should be between 0 and 1.
        //
        // Unfortunately I could not figure out why this is the case and therefore just
        // rescaled the relevance value accordingly.
        // - Moritz (badnames)
        let alpha = (relevance - 0.5) * 512.0;

        *pixel = Rgba([red as u8, green as u8, blue as u8, alpha as u8]);
    }

    let mut buffer: Vec<u8> = Vec::new();
    imgbuf
        .write_to(&mut Cursor::new(&mut buffer), image::ImageOutputFormat::Png)
        .map_err(|err| ServiceError::new(StatusCode::INTERNAL_SERVER_ERROR, &err.to_string()))?;
    Ok(buffer)
}

/// Get spatial relations of a certain plant.
///
/// # Errors
/// * If the connection to the database could not be established.
/// * If the SQL query failed.
pub async fn find_relations(
    search_query: RelationSearchParameters,
    app_data: &Data<AppDataInner>,
) -> Result<RelationsDto, ServiceError> {
    let mut conn = app_data.pool.get().await?;
    let result = plant_layer::find_relations(search_query, &mut conn).await?;
    Ok(result)
}