package org.terst.feedreader.ui

import org.junit.Assert.assertEquals
import org.junit.Assert.assertNull
import org.junit.Assert.assertTrue
import org.junit.Test

class ImageZoomTest {

    @Test
    fun `a bare image is wrapped in a zoom link pointing at its own source`() {
        val html = linkifyImagesForZoom("""<p>hi</p><img src="https://ex.com/a.jpg" alt="x">""")
        assertEquals(
            """<p>hi</p><a href="feedreader-image:https://ex.com/a.jpg"><img src="https://ex.com/a.jpg" alt="x"></a>""",
            html
        )
    }

    @Test
    fun `an image already inside a link is left alone`() {
        // The YouTube thumbnail ReaderExtractor synthesizes is exactly this shape -- wrapping it
        // again would swallow the tap that's supposed to play the video.
        val original =
            """<a href="https://www.youtube.com/watch?v=abcdefghijk"><img src="https://i.ytimg.com/vi/x/hq720.jpg"></a>"""
        assertEquals(original, linkifyImagesForZoom(original))
    }

    @Test
    fun `an image after a closed link is still wrapped`() {
        val html = linkifyImagesForZoom("""<a href="https://ex.com/">t</a><img src="https://ex.com/a.png">""")
        assertTrue(html.endsWith("""<a href="feedreader-image:https://ex.com/a.png"><img src="https://ex.com/a.png"></a>"""))
    }

    @Test
    fun `a protocol-relative image source becomes an https zoom target`() {
        val html = linkifyImagesForZoom("""<img src="//ex.com/a.jpg">""")
        assertEquals("""<a href="feedreader-image:https://ex.com/a.jpg"><img src="//ex.com/a.jpg"></a>""", html)
    }

    @Test
    fun `a relative image source is left alone`() {
        // Relative srcs resolve against the WebView's base URL, which a custom-scheme href
        // can't reproduce -- better to leave the image un-zoomable than to build a dead link.
        val original = """<img src="/local/a.jpg">"""
        assertEquals(original, linkifyImagesForZoom(original))
    }

    @Test
    fun `a data uri image is left alone`() {
        val original = """<img src="data:image/png;base64,AAAA">"""
        assertEquals(original, linkifyImagesForZoom(original))
    }

    @Test
    fun `wrapping is not confused by tags that merely start with the letter a`() {
        val html = linkifyImagesForZoom("""<abbr title="x">y</abbr><img src="https://ex.com/a.jpg">""")
        assertTrue(html.contains("""<a href="feedreader-image:https://ex.com/a.jpg">"""))
    }

    @Test
    fun `a zoom-scheme url resolves back to the image it wraps`() {
        assertEquals("https://ex.com/a.jpg", zoomableImageTarget("feedreader-image:https://ex.com/a.jpg"))
    }

    @Test
    fun `a plain link straight to an image file is a zoom target too`() {
        // WordPress's default "link to media file" wraps article images in exactly this --
        // the image is inside an <a>, so it never gets a zoom-scheme href of its own.
        assertEquals("https://ex.com/photo.JPEG?w=900", zoomableImageTarget("https://ex.com/photo.JPEG?w=900"))
    }

    @Test
    fun `an ordinary article link is not a zoom target`() {
        assertNull(zoomableImageTarget("https://ex.com/2026/09/some-article"))
    }

    @Test
    fun `an svg link is not a zoom target`() {
        // Coil's default decoders can't render SVG, so a viewer opened on one shows nothing.
        assertNull(zoomableImageTarget("https://ex.com/icon.svg"))
    }

    @Test
    fun `reader html makes an article's own images zoomable`() {
        val html = wrapReaderHtml("""<p>x</p><img src="https://ex.com/a.jpg">""")
        assertTrue(html.contains("""<a href="feedreader-image:https://ex.com/a.jpg"><img src="https://ex.com/a.jpg"></a>"""))
    }

    @Test
    fun `reader html makes the synthesized hero image zoomable too`() {
        val html = wrapReaderHtml("<p>no image of its own</p>", imageUrl = "https://ex.com/hero.jpg")
        assertTrue(html.contains("""<a href="feedreader-image:https://ex.com/hero.jpg">"""))
        assertTrue(html.contains("""class="article-hero""""))
    }

    @Test
    fun `reader html leaves a youtube thumbnail tapping through to the video`() {
        // The thumbnail is synthesized from an <iframe> during wrapping, after which it's an
        // image inside a link -- the zoom pass has to run late enough to see it as one.
        val html = wrapReaderHtml("""<iframe src="https://www.youtube.com/embed/abcdefghijk"></iframe>""")
        assertTrue(html.contains("""<a href="https://www.youtube.com/watch?v=abcdefghijk">"""))
        assertTrue(!html.contains("feedreader-image:https://i.ytimg.com"))
    }

    @Test
    fun `long-pressing a zoom-wrapped image offers the real image url, not the internal scheme`() {
        assertEquals("https://ex.com/a.jpg", withoutImageZoomScheme("feedreader-image:https://ex.com/a.jpg"))
        assertEquals("https://ex.com/page", withoutImageZoomScheme("https://ex.com/page"))
    }

    @Test
    fun `pinching out scales the image up`() {
        assertEquals(2f, imageZoomScale(1f, 2f), 0.001f)
    }

    @Test
    fun `the image never zooms out past its fitted size`() {
        assertEquals(1f, imageZoomScale(1.2f, 0.1f), 0.001f)
    }

    @Test
    fun `the image never zooms in past the maximum scale`() {
        assertEquals(IMAGE_ZOOM_MAX_SCALE, imageZoomScale(4f, 10f), 0.001f)
    }

    @Test
    fun `double-tapping an unzoomed image zooms it in`() {
        assertTrue(imageZoomDoubleTapScale(1f) > 1f)
    }

    @Test
    fun `double-tapping a zoomed image returns it to its fitted size`() {
        assertEquals(1f, imageZoomDoubleTapScale(imageZoomDoubleTapScale(1f)), 0.001f)
    }

    @Test
    fun `an unzoomed image cannot be panned`() {
        assertEquals(0f, clampImagePanOffset(400f, viewportSize = 1000f, contentSize = 1000f, scale = 1f), 0.001f)
    }

    @Test
    fun `a zoomed image pans up to the edge of its scaled self`() {
        // At 2x over a 1000px viewport the image is 2000px wide, so 500px of it hangs off
        // each side -- that's exactly how far it may be dragged before showing empty space.
        assertEquals(500f, clampImagePanOffset(9000f, 1000f, 1000f, 2f), 0.001f)
        assertEquals(-500f, clampImagePanOffset(-9000f, 1000f, 1000f, 2f), 0.001f)
        assertEquals(120f, clampImagePanOffset(120f, 1000f, 1000f, 2f), 0.001f)
    }

    @Test
    fun `panning is bounded by the image itself, not by the viewport it sits in`() {
        // A wide photo letterboxed into a square viewport: at 2x it's 1000x1000 again, so it
        // still fills the viewport exactly and there's nothing off-screen to pan to
        // vertically -- bounding by the viewport instead would let it be dragged into the
        // black bars above and below it.
        assertEquals(0f, clampImagePanOffset(400f, 1000f, 500f, 2f), 0.001f)
        // ...but at 4x it's 2000px tall over a 1000px viewport, so 500px hangs off each edge.
        assertEquals(500f, clampImagePanOffset(9000f, 1000f, 500f, 4f), 0.001f)
    }

    @Test
    fun `a wide image is fitted to the viewport's width, leaving bars above and below`() {
        assertEquals(1000f to 500f, fittedImageSize(1000f, 1000f, 2000f, 1000f))
    }

    @Test
    fun `a tall image is fitted to the viewport's height`() {
        assertEquals(500f to 1000f, fittedImageSize(1000f, 1000f, 1000f, 2000f))
    }

    @Test
    fun `a drag on a zoomed image pans it`() {
        // The regression this function exists for: the viewer computed its pan bounds from
        // values captured once at composition (viewport still zero, image not yet decoded),
        // which pinned every offset to 0 -- a zoomed image simply refused to pan.
        val panned = imageZoomTransform(
            ImageZoomState(scale = 2f),
            viewportSize = 1000f to 1000f,
            intrinsicSize = 1000f to 1000f,
            pan = -100f to -50f,
            gestureZoom = 1f
        )
        assertEquals(2f, panned.scale, 0.001f)
        assertEquals(-100f, panned.offsetX, 0.001f)
        assertEquals(-50f, panned.offsetY, 0.001f)
    }

    @Test
    fun `a drag on an unzoomed image leaves it where it is`() {
        val panned = imageZoomTransform(
            ImageZoomState(scale = 1f),
            viewportSize = 1000f to 1000f,
            intrinsicSize = 1000f to 1000f,
            pan = 100f to 100f,
            gestureZoom = 1f
        )
        assertEquals(0f, panned.offsetX, 0.001f)
        assertEquals(0f, panned.offsetY, 0.001f)
    }

    @Test
    fun `a pan stops at the edge of the scaled image`() {
        val panned = imageZoomTransform(
            ImageZoomState(scale = 2f, offsetX = 400f),
            viewportSize = 1000f to 1000f,
            intrinsicSize = 1000f to 1000f,
            pan = 300f to 0f,
            gestureZoom = 1f
        )
        assertEquals(500f, panned.offsetX, 0.001f)
    }

    @Test
    fun `a pinch zooms and clamps the existing pan to the new scale`() {
        val zoomedOut = imageZoomTransform(
            ImageZoomState(scale = 2f, offsetX = 500f, offsetY = 500f),
            viewportSize = 1000f to 1000f,
            intrinsicSize = 1000f to 1000f,
            pan = 0f to 0f,
            gestureZoom = 0.1f
        )
        assertEquals(1f, zoomedOut.scale, 0.001f)
        assertEquals(0f, zoomedOut.offsetX, 0.001f)
        assertEquals(0f, zoomedOut.offsetY, 0.001f)
    }

    @Test
    fun `a letterboxed image pans along its long axis only`() {
        // A 2000x1000 photo fitted into a 1000x1000 viewport is 1000x500 on screen, so at 2x
        // it fills the viewport exactly -- there's nothing above or below it to pan to, but
        // dragging sideways still works.
        val panned = imageZoomTransform(
            ImageZoomState(scale = 2f),
            viewportSize = 1000f to 1000f,
            intrinsicSize = 2000f to 1000f,
            pan = -200f to 300f,
            gestureZoom = 1f
        )
        assertEquals(-200f, panned.offsetX, 0.001f)
        assertEquals(0f, panned.offsetY, 0.001f)
    }

    @Test
    fun `an image that hasn't reported its size yet can still be panned`() {
        // Coil reports intrinsic size only once the image decodes; a pinch-and-drag before
        // then is bounded by the viewport rather than refusing to move.
        val panned = imageZoomTransform(
            ImageZoomState(scale = 2f),
            viewportSize = 1000f to 1000f,
            intrinsicSize = 0f to 0f,
            pan = -300f to 0f,
            gestureZoom = 1f
        )
        assertEquals(-300f, panned.offsetX, 0.001f)
    }

    @Test
    fun `double-tapping zooms in from the fitted size`() {
        val zoomed = imageZoomDoubleTap(ImageZoomState(), 1000f to 1000f, 1000f to 1000f)
        assertTrue(zoomed.scale > 1f)
    }

    @Test
    fun `double-tapping a panned, zoomed image returns it to fitted and centered`() {
        val reset = imageZoomDoubleTap(
            ImageZoomState(scale = 3f, offsetX = 300f, offsetY = -200f),
            1000f to 1000f,
            1000f to 1000f
        )
        assertEquals(1f, reset.scale, 0.001f)
        assertEquals(0f, reset.offsetX, 0.001f)
        assertEquals(0f, reset.offsetY, 0.001f)
    }

    @Test
    fun `an image whose size isn't known yet is assumed to fill the viewport`() {
        // Coil only reports intrinsic size once the image has actually decoded; until then
        // panning has to be bounded by something, and the viewport is the safe guess.
        assertEquals(1000f to 800f, fittedImageSize(1000f, 800f, 0f, 0f))
        assertEquals(1000f to 800f, fittedImageSize(1000f, 800f, Float.NaN, Float.NaN))
    }
}