//! This library provide a single function [`make_quote_image`] to turn somebody's quote into an
//! image.
//!
//! This is not an feature rich library. You may meet some draw issue. Feel free to open issue
//! at GitHub to help me improve this library. Currently the best practice is to set the output
//! size to 1920x1080.
//!
//! # Usage
//!
//! ```rust
//! use make_quote::{QuoteProducer, ImgConfig};
//!
//! // First of all, load an font into memory
//! let font = std::fs::read("/usr/share/fonts/noto-cjk/NotoSansCJK-Regular.ttc").unwrap();
//!
//! // Create a image producer
//! let producer = QuoteProducer::builder()
//!     .font(&font)
//!     .output_size(1920, 1080) // optional
//!     .font_scale(120.0)       // optional
//!     .build();
//!
//! // Create image configuration
//! let config = ImgConfig::builder()
//!     .username("V5电竞俱乐部中单选手 Otto")
//!     .avatar_path("./assets/avatar.png")
//!     .quote("大家好，今天来点大家想看的东西。")
//!     .build();
//!
//! // Then generate the image and get the image buffer
//! let buffer = producer.make_image(&config).unwrap();
//!
//! // You can do anything you like to the buffer, save it or just send it through the net.
//! std::fs::write("./assets/test.jpg", buffer).unwrap();
//! ```
//!
//! This will generate the below output:
//!
//! <img src="https://github.com/Avimitin/make-quote/raw/master/assets/test.jpg"/>

use std::fmt::Display;
use std::io::Cursor;
use std::path::{Path, PathBuf};

use image::{
    imageops::{self, FilterType},
    ImageBuffer, ImageError, ImageFormat, Pixel, Rgba, RgbaImage,
};
use imageproc::drawing::draw_text_mut;
use rusttype::{Font, Scale};
use typed_builder::TypedBuilder;

#[derive(TypedBuilder)]
pub struct QuoteProducer<'font> {
    #[builder(default = (1920, 1080), setter( transform = |width: u32, height: u32| (width, height) ))]
    output_size: (u32, u32),
    #[builder(default = 120.0)]
    font_scale: f32,
    #[builder(setter( transform = |raw: &'font [u8]|
        Font::try_from_bytes(raw).unwrap_or_else(|| panic!("invalid font data"))
    ))]
    font: Font<'font>,
}

#[derive(TypedBuilder)]
pub struct ImgConfig {
    #[builder(setter( transform = |s: impl Display| s.to_string() ))]
    quote: String,
    #[builder(setter( transform = |s: impl Display| s.to_string() ))]
    username: String,
    #[builder(setter( transform = |p: impl AsRef<Path>| p.as_ref().to_path_buf() ))]
    avatar_path: PathBuf,
}

impl<'font> QuoteProducer<'font> {
    pub fn make_image(&self, config: &ImgConfig) -> Result<Vec<u8>> {
        let black = Rgba([0, 0, 0, 255]);
        let (bg_width, bg_height) = self.output_size;

        let mut background = RgbaImage::from_pixel(bg_width, bg_height, black);
        let avatar = self.produce_avatar(&config.avatar_path)?;
        let gradient = self.produce_gradient(avatar.width());

        // Step 1: Overlay avatar to background
        imageops::overlay(&mut background, &avatar, 0, 0);

        // Step 2: Overlay black gradient to avatar
        let offset = (avatar.width() - gradient.width()) as i64;
        imageops::overlay(&mut background, &gradient, offset, 0);

        // Step 3: Draw font on background
        self.draw_quote(&mut background, config, avatar.width())?;

        let mut buffer = Cursor::new(Vec::new());
        background.write_to(&mut buffer, ImageFormat::Jpeg)?;
        Ok(buffer.into_inner())
    }

    /// Scale and crop the avatar to fit the background.
    fn produce_avatar(&self, avatar: impl AsRef<Path>) -> Result<RgbaImgBuf> {
        let buffer = image::open(avatar)?.into_rgba8();

        let ratio = buffer.width() as f32 / buffer.height() as f32;
        let bg_height = self.output_size.1;
        let new_width = (bg_height as f32 * ratio) as u32;

        // scale avatar size to background height
        let mut buffer = imageops::resize(&buffer, new_width, bg_height, FilterType::Nearest);

        // crop 1/4 from left
        let keep_width = buffer.width() - (buffer.width() / 4);
        Ok(imageops::crop(&mut buffer, new_width / 4, 0, keep_width, bg_height).to_image())
    }

    /// Create a transparent to black gradient overlay
    fn produce_gradient(&self, avatar_width: u32) -> RgbaImgBuf {
        let mut gradient_overlay = RgbaImage::new(avatar_width / 3, self.output_size.1);
        let start = Rgba::from_slice(&[0, 0, 0, 0]);
        let end = Rgba::from_slice(&[0, 0, 0, 255]);
        imageops::horizontal_gradient(&mut gradient_overlay, start, end);
        gradient_overlay
    }

    /// Draw quote on background
    fn draw_quote(&self, bg: &mut RgbaImgBuf, config: &ImgConfig, avatar_width: u32) -> Result<()> {
        let font = &self.font;
        let white = Rgba([255, 255, 255, 255]);
        let gray = Rgba([147, 147, 147, 255]);
        let (bg_width, bg_height) = self.output_size;
        let quote_font_scale = self.font_scale;
        let username_font_scale = quote_font_scale - 40.0;
        let quote_text_scale = Scale::uniform(quote_font_scale);
        let username_text_scale = Scale::uniform(username_font_scale);

        let quote_lines = split_quotes(&config.quote);
        let (quote_text_width, quote_text_height) =
            imageproc::drawing::text_size(quote_text_scale, font, &quote_lines[0]);

        let blank_width = bg_width - avatar_width;
        let text_gap = blank_width as i32 - quote_text_width;
        let text_draw_x_offset: i32 = avatar_width as i32 + (text_gap / 2);
        let mut text_draw_y_offset: i32 = (bg_height as i32 / 3) - quote_text_height;

        for quote in split_quotes(&config.quote) {
            draw_text_mut(
                bg,
                white,
                text_draw_x_offset,
                text_draw_y_offset,
                quote_text_scale,
                font,
                &quote,
            );

            text_draw_y_offset += quote_font_scale as i32;
        }

        let (usr_text_width, _) =
            imageproc::drawing::text_size(username_text_scale, font, &config.username);
        let text_draw_x_offset = (text_draw_x_offset + quote_text_width / 2) - usr_text_width / 2;
        draw_text_mut(
            bg,
            gray,
            text_draw_x_offset,
            text_draw_y_offset + (quote_font_scale as i32),
            username_text_scale,
            font,
            &format!("– {}", config.username),
        );

        Ok(())
    }
}

#[derive(thiserror::Error, Debug)]
pub enum ErrorKind {
    #[error("internal image library error: {0}")]
    ImgErr(#[from] ImageError),
    #[error("fail to read font: {0}")]
    FontErr(#[from] std::io::Error),
}

type Result<T, E = ErrorKind> = core::result::Result<T, E>;

/// Alias to the RGBA image buffer type
type RgbaImgBuf = ImageBuffer<Rgba<u8>, Vec<u8>>;

/// Split long string to multiline
fn split_quotes(quote: &str) -> Vec<String> {
    let max_length = 12;
    quote
        .lines()
        .flat_map(|line| {
            let chars = line.chars().collect::<Vec<_>>();
            chars
                .chunks(max_length)
                .map(|chk| chk.iter().collect::<String>())
                .collect::<Vec<_>>()
        })
        .collect::<Vec<String>>()
}

#[test]
fn test_create_background_image() {
    use std::time::Instant;

    let font = std::fs::read("/usr/share/fonts/noto-cjk/NotoSansCJK-Regular.ttc").unwrap();
    let builder = QuoteProducer::builder().font(&font).build();

    let config = ImgConfig::builder()
        .username("V5电竞俱乐部中单选手 Otto")
        .avatar_path("./assets/avatar.png")
        .quote("大家好，今天来点大家想看的东西。")
        .build();

    let now = Instant::now();
    let buffer = builder.make_image(&config).unwrap();
    std::fs::write("./assets/test.jpg", buffer).unwrap();
    println!("elapsed: {} ms", now.elapsed().as_millis());
}