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1	import XCTest
2	import CoreGraphics
3	@testable import LChatCore
4
5	// 🤖 Pins the CGImage adaptation of the reference BlurHash (woltapp/blurhash's
6	// Swift files are UIImage-only and copy-in by design — no package): structure,
7	// round-trip colour fidelity, and malformed-hash rejection. A DCT port's bugs
8	// are subtle; these tests are the confidence the adaptation didn't drift.
9	final class BlurhashTests: XCTestCase {
10	private func solid(_ r: CGFloat, _ g: CGFloat, _ b: CGFloat,
11	w: Int = 32, h: Int = 24) -> CGImage {
12	let cs = CGColorSpaceCreateDeviceRGB()
13	let ctx = CGContext(data: nil, width: w, height: h, bitsPerComponent: 8,
14	bytesPerRow: w * 4, space: cs,
15	bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)!
16	// Components in the context's OWN space — the CGColor(red:green:blue:)
17	// convenience creates a generic-space colour that CG converts on draw
18	// (0.3 arrived as 0.405), which read as a codec bug.
19	ctx.setFillColor(CGColor(colorSpace: cs, components: [r, g, b, 1])!)
20	ctx.fill(CGRect(x: 0, y: 0, width: w, height: h))
21	return ctx.makeImage()!
22	}
23
24	private func averageRGB(_ image: CGImage) -> (Double, Double, Double) {
25	let w = image.width, h = image.height
26	var data = [UInt8](repeating: 0, count: w * h * 4)
27	let cs = CGColorSpaceCreateDeviceRGB()
28	let ctx = CGContext(data: &data, width: w, height: h, bitsPerComponent: 8,
29	bytesPerRow: w * 4, space: cs,
30	bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)!
31	ctx.draw(image, in: CGRect(x: 0, y: 0, width: w, height: h))
32	var r = 0.0, g = 0.0, b = 0.0
33	for i in stride(from: 0, to: data.count, by: 4) {
34	r += Double(data[i]); g += Double(data[i + 1]); b += Double(data[i + 2])
35	}
36	let n = Double(w * h)
37	return (r / n, g / n, b / n)
38	}
39
40	func testHashShape() throws {
41	let hash = try XCTUnwrap(Blurhash.encode(solid(0.8, 0.3, 0.2)))
42	// 4×3 components: 1 (size) + 1 (max AC) + 4 (DC) + 2×11 (AC) = 28 chars.
43	XCTAssertEqual(hash.count, 28)
44	}
45
46	// The shared vector grid: 8×6 RGBA, red ramps left→right, green top→bottom,
47	// blue fixed at 64 — keep IDENTICAL to vectorGrid() in test/blurhash.test.mjs.
48	private func vectorImage() -> CGImage {
49	let w = 8, h = 6
50	var px = [UInt8](repeating: 0, count: w * h * 4)
51	for y in 0..<h {
52	for x in 0..<w {
53	let o = (y * w + x) * 4
54	px[o] = UInt8((x * 255 + (w - 1) / 2) / (w - 1))
55	px[o + 1] = UInt8((y * 255 + (h - 1) / 2) / (h - 1))
56	px[o + 2] = 64
57	px[o + 3] = 255
58	}
59	}
60	let cs = CGColorSpaceCreateDeviceRGB()
61	let provider = CGDataProvider(data: Data(px) as CFData)!
62	return CGImage(width: w, height: h, bitsPerComponent: 8, bitsPerPixel: 32,
63	bytesPerRow: w * 4, space: cs,
64	bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.noneSkipLast.rawValue),
65	provider: provider, decode: nil, shouldInterpolate: false,
66	intent: .defaultIntent)!
67	}
68
69	func testCrossImplementationVector() throws {
70	// The one true hash for the vector grid — test/blurhash.test.mjs pins
71	// the same string. A change here without the twin is a platform drift.
72	XCTAssertEqual(try XCTUnwrap(Blurhash.encode(vectorImage())),
73	"LyI5d=39a|%0z2NKfQnSeXf7fQf7")
74	}
75
76	func testRoundTripPreservesColour() throws {
77	for (r, g, b) in [(1.0, 0.2, 0.2), (0.1, 0.7, 0.3), (0.2, 0.3, 0.9)] {
78	let hash = try XCTUnwrap(Blurhash.encode(solid(r, g, b)))
79	let decoded = try XCTUnwrap(Blurhash.decode(hash))
80	let avg = averageRGB(decoded)
81	XCTAssertEqual(avg.0 / 255, r, accuracy: 0.06, "red channel for \(hash)")
82	XCTAssertEqual(avg.1 / 255, g, accuracy: 0.06, "green channel for \(hash)")
83	XCTAssertEqual(avg.2 / 255, b, accuracy: 0.06, "blue channel for \(hash)")
84	}
85	}
86
87	func testGradientRoundTripKeepsOrientation() throws {
88	// Left-red, right-blue: the decode must keep the gradient's direction.
89	let w = 32, h = 24
90	let cs = CGColorSpaceCreateDeviceRGB()
91	let ctx = CGContext(data: nil, width: w, height: h, bitsPerComponent: 8,
92	bytesPerRow: w * 4, space: cs,
93	bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)!
94	ctx.setFillColor(CGColor(colorSpace: cs, components: [1, 0, 0, 1])!)
95	ctx.fill(CGRect(x: 0, y: 0, width: w / 2, height: h))
96	ctx.setFillColor(CGColor(colorSpace: cs, components: [0, 0, 1, 1])!)
97	ctx.fill(CGRect(x: w / 2, y: 0, width: w / 2, height: h))
98	let hash = try XCTUnwrap(Blurhash.encode(ctx.makeImage()!))
99	let decoded = try XCTUnwrap(Blurhash.decode(hash, width: 32, height: 24))
100	var left = [UInt8](repeating: 0, count: 4), right = left
101	let dctx = { (px: Int, out: inout [UInt8]) in
102	let c = CGContext(data: &out, width: 1, height: 1, bitsPerComponent: 8,
103	bytesPerRow: 4, space: cs,
104	bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)!
105	c.draw(decoded, in: CGRect(x: -px, y: 0, width: 32, height: 24))
106	}
107	dctx(2, &left)
108	dctx(29, &right)
109	XCTAssertGreaterThan(left[0], left[2], "left edge reads red")
110	XCTAssertGreaterThan(right[2], right[0], "right edge reads blue")
111	}
112
113	func testMalformedHashesRejected() {
114	XCTAssertNil(Blurhash.decode(""))
115	XCTAssertNil(Blurhash.decode("LEHV6")) // truncated
116	XCTAssertNil(Blurhash.decode("LEHV6nWB2yk8pyo0adR*.7kCMdnj!!")) // wrong length
117	XCTAssertNil(Blurhash.decode(String(repeating: "\u{1F600}", count: 28))) // non-base83
118	}
119	}
120