// SPDX-License-Identifier: LGPL-2.1-only
// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>

use std::sync::Arc;
use crate::types::Rect;
use crate::render::Canvas;

/// A static image widget that renders RGBA pixel data.
///
/// Images are scaled to fill their allocated rect. Alpha blending against the
/// background is handled automatically (straight → premultiplied conversion).
///
/// The pixel buffer is shared via `Arc` so reusing the same image across
/// frames (e.g. a background decoded once at startup) is a cheap pointer
/// copy instead of a full `Vec<u8>` clone.
///
/// ```rust,no_run
/// # use std::sync::Arc;
/// # use ltk::{ img_widget, Element };
/// # #[ derive( Clone ) ] enum Msg {}
/// # fn _ex( rgba_bytes: Arc<Vec<u8>>, width: u32, height: u32 ) -> Element<Msg> {
/// img_widget( rgba_bytes, width, height )
///     .opacity( 0.8 )
/// .into()
/// # }
/// ```
pub struct Image
{
	/// Raw RGBA pixel data (4 bytes per pixel, straight alpha).
	pub rgba:    Arc<Vec<u8>>,
	/// Pixel width of the source image.
	pub width:   u32,
	/// Pixel height of the source image.
	pub height:  u32,
	/// When `true` the image scales to fill the available width (cover mode).
	pub cover:   bool,
	/// Optional explicit display size in logical pixels.
	pub display_size: Option<( f32, f32 )>,
	/// Opacity multiplier in `[0.0, 1.0]`. Default: `1.0`.
	pub opacity: f32,
}

impl Image
{
	/// Create an image from a shared RGBA buffer.
	///
	/// `width` and `height` must match the dimensions of `rgba`.
	pub fn new( rgba: Arc<Vec<u8>>, width: u32, height: u32 ) -> Self
	{
		Self { rgba, width, height, cover: false, display_size: None, opacity: 1.0 }
	}

	/// Load an image from a file path. Supports PNG, JPEG, and other formats
	/// supported by the [`image`](https://crates.io/crates/image) crate.
	pub fn from_path( path: &str ) -> Result<Self, Box<dyn std::error::Error>>
	{
		let img = image::open( path )?.into_rgba8();
		let ( width, height ) = img.dimensions();
		Ok( Self { rgba: Arc::new( img.into_raw() ), width, height, cover: false, display_size: None, opacity: 1.0 } )
	}

	/// Scale the image to fill the available width, preserving aspect ratio (cover mode).
	pub fn cover( mut self ) -> Self
	{
		self.cover = true;
		self
	}

	/// Set an explicit display size in logical pixels.
	pub fn size( mut self, width: f32, height: f32 ) -> Self
	{
		self.display_size = Some( ( width.max( 0.0 ), height.max( 0.0 ) ) );
		self
	}

	/// Set the opacity multiplier. Clamped to `[0.0, 1.0]`.
	pub fn opacity( mut self, o: f32 ) -> Self
	{
		self.opacity = o.clamp( 0.0, 1.0 );
		self
	}

	/// Return the preferred `(width, height)` given available `max_width`.
	pub fn preferred_size( &self, max_width: f32 ) -> (f32, f32)
	{
		if let Some( size ) = self.display_size
		{
			return size;
		}
		if self.cover
		{
			( max_width, max_width * self.height as f32 / self.width as f32 )
		} else {
			let scale = max_width / self.width as f32;
			( max_width, self.height as f32 * scale )
		}
	}

	/// Draw the image into `canvas` at `rect`.
	pub fn draw( &self, canvas: &mut Canvas, rect: Rect )
	{
		canvas.draw_image_data( &self.rgba[..], self.width, self.height, rect, self.opacity );
	}
}

#[ cfg( test ) ]
mod tests
{
	use super::*;

	fn solid_rgba( w: u32, h: u32 ) -> Arc<Vec<u8>>
	{
		Arc::new( vec![ 255u8; ( w * h * 4 ) as usize ] )
	}

	// ── builders / defaults ───────────────────────────────────────────────────

	#[ test ]
	fn new_uses_documented_defaults()
	{
		let img = Image::new( solid_rgba( 4, 4 ), 4, 4 );
		assert_eq!( img.width,  4 );
		assert_eq!( img.height, 4 );
		assert!( !img.cover );
		assert!( img.display_size.is_none() );
		assert_eq!( img.opacity, 1.0 );
	}

	#[ test ]
	fn cover_builder_sets_cover_flag()
	{
		let img = Image::new( solid_rgba( 4, 4 ), 4, 4 ).cover();
		assert!( img.cover );
	}

	#[ test ]
	fn size_builder_sets_explicit_display_size()
	{
		let img = Image::new( solid_rgba( 4, 4 ), 4, 4 ).size( 120.0, 80.0 );
		assert_eq!( img.display_size, Some( ( 120.0, 80.0 ) ) );
	}

	#[ test ]
	fn size_builder_clamps_negative_dimensions_to_zero()
	{
		let img = Image::new( solid_rgba( 4, 4 ), 4, 4 ).size( -10.0, -20.0 );
		assert_eq!( img.display_size, Some( ( 0.0, 0.0 ) ) );
	}

	#[ test ]
	fn opacity_clamps_to_unit_interval()
	{
		assert_eq!( Image::new( solid_rgba( 1, 1 ), 1, 1 ).opacity( -0.5 ).opacity, 0.0 );
		assert_eq!( Image::new( solid_rgba( 1, 1 ), 1, 1 ).opacity(  1.5 ).opacity, 1.0 );
		assert_eq!( Image::new( solid_rgba( 1, 1 ), 1, 1 ).opacity(  0.5 ).opacity, 0.5 );
	}

	// ── preferred_size ────────────────────────────────────────────────────────

	#[ test ]
	fn preferred_size_default_scales_height_to_match_width_aspect()
	{
		// 200×100 source image at max_width = 400 → scale = 2 → height 200.
		let img = Image::new( solid_rgba( 200, 100 ), 200, 100 );
		let ( w, h ) = img.preferred_size( 400.0 );
		assert_eq!( w, 400.0 );
		assert_eq!( h, 200.0 );
	}

	#[ test ]
	fn preferred_size_with_explicit_size_wins_over_aspect_logic()
	{
		let img = Image::new( solid_rgba( 200, 100 ), 200, 100 ).size( 50.0, 25.0 );
		assert_eq!( img.preferred_size( 1000.0 ), ( 50.0, 25.0 ) );
	}

	#[ test ]
	fn preferred_size_cover_mode_keeps_aspect_ratio()
	{
		// 100×50 source in cover mode at max_width = 300 → height = 300 * (50/100) = 150.
		let img = Image::new( solid_rgba( 100, 50 ), 100, 50 ).cover();
		let ( w, h ) = img.preferred_size( 300.0 );
		assert_eq!( w, 300.0 );
		assert_eq!( h, 150.0 );
	}

	#[ test ]
	fn preferred_size_cover_and_default_match_for_uniform_scaling()
	{
		// When the source aspect matches the requested width, cover and the
		// default fit-width path produce identical sizes — they only diverge
		// when the source is taller than wide.
		let normal  = Image::new( solid_rgba( 100, 50 ), 100, 50 );
		let covered = Image::new( solid_rgba( 100, 50 ), 100, 50 ).cover();
		assert_eq!( normal.preferred_size( 200.0 ), covered.preferred_size( 200.0 ) );
	}

	// ── Arc sharing ───────────────────────────────────────────────────────────

	#[ test ]
	fn rgba_buffer_is_shared_via_arc_not_cloned_per_image()
	{
		let bytes = solid_rgba( 8, 8 );
		let strong_before = Arc::strong_count( &bytes );

		let img = Image::new( bytes.clone(), 8, 8 );
		assert_eq!( Arc::strong_count( &bytes ), strong_before + 1 );

		// Same buffer goes into a second image — strong count rises again.
		let img2 = Image::new( bytes.clone(), 8, 8 );
		assert_eq!( Arc::strong_count( &bytes ), strong_before + 2 );

		drop( img );
		drop( img2 );
		assert_eq!( Arc::strong_count( &bytes ), strong_before );
	}
}