tilt-shift-camera/app/src/main/java/no/naiv/tiltshift/effect/TiltShiftRenderer.kt

package no.naiv.tiltshift.effect

import android.content.Context
import android.graphics.SurfaceTexture
import android.opengl.GLES11Ext
import android.opengl.GLES20
import android.opengl.GLSurfaceView
import android.util.Log
import android.view.Surface
import java.nio.ByteBuffer
import java.nio.ByteOrder
import java.nio.FloatBuffer
import javax.microedition.khronos.egl.EGLConfig
import javax.microedition.khronos.opengles.GL10

/**
 * OpenGL renderer for applying tilt-shift effect to camera preview
 * using a two-pass separable Gaussian blur.
 *
 * Rendering pipeline (3 draw calls per frame):
 * 1. **Passthrough**: camera texture → FBO-A (handles coordinate transform via vertex/texcoord)
 * 2. **Horizontal blur**: FBO-A → FBO-B (13-tap Gaussian, tilt-shift mask)
 * 3. **Vertical blur**: FBO-B → screen (13-tap Gaussian, tilt-shift mask)
 *
 * The passthrough decouples the camera's rotated coordinate system from the blur
 * passes, which work entirely in screen space.
 */
class TiltShiftRenderer(
    private val context: Context,
    private val onSurfaceTextureAvailable: (SurfaceTexture) -> Unit,
    private val onFrameAvailable: () -> Unit
) : GLSurfaceView.Renderer {

    companion object {
        private const val TAG = "TiltShiftRenderer"
    }

    private lateinit var shader: TiltShiftShader
    private var surfaceTexture: SurfaceTexture? = null
    private var cameraTextureId: Int = 0

    // Camera quad: crop-to-fill vertices + rotated texcoords (pass 1 only)
    private lateinit var cameraVertexBuffer: FloatBuffer
    private lateinit var cameraTexCoordBuffer: FloatBuffer

    // Fullscreen quad for blur passes (no crop, standard texcoords)
    private lateinit var fullscreenVertexBuffer: FloatBuffer
    private lateinit var fullscreenTexCoordBuffer: FloatBuffer

    private var surfaceWidth: Int = 0
    private var surfaceHeight: Int = 0

    // FBO resources: one framebuffer, two color textures for ping-pong
    private var fboId: Int = 0
    private var fboTexA: Int = 0
    private var fboTexB: Int = 0

    // Current effect parameters (updated from UI thread)
    @Volatile
    var blurParameters: BlurParameters = BlurParameters.DEFAULT

    @Volatile
    private var isFrontCamera: Boolean = false

    // Camera resolution for aspect ratio correction (set from UI thread)
    @Volatile
    private var cameraWidth: Int = 0
    @Volatile
    private var cameraHeight: Int = 0
    @Volatile
    private var vertexBufferDirty: Boolean = false

    // Texture coordinates for the back camera, indexed by Surface.ROTATION_*.
    // The base orientation (index 0) applies the 90° CCW rotation that maps
    // the landscape sensor frame to a portrait display. Indices 1/2/3 layer
    // additional CCW rotations on top so the activity's rotation is
    // compensated and world-up stays at clip-space-top.
    private val texCoordsBackByRotation = arrayOf(
        floatArrayOf(1f, 1f, 1f, 0f, 0f, 1f, 0f, 0f), // ROTATION_0
        floatArrayOf(1f, 0f, 0f, 0f, 1f, 1f, 0f, 1f), // ROTATION_90
        floatArrayOf(0f, 0f, 0f, 1f, 1f, 0f, 1f, 1f), // ROTATION_180
        floatArrayOf(0f, 1f, 1f, 1f, 0f, 0f, 1f, 0f)  // ROTATION_270
    )

    // Front camera variants: same as back, but horizontally mirrored
    // for the natural selfie view.
    private val texCoordsFrontByRotation = arrayOf(
        floatArrayOf(0f, 1f, 0f, 0f, 1f, 1f, 1f, 0f), // ROTATION_0
        floatArrayOf(0f, 0f, 1f, 0f, 0f, 1f, 1f, 1f), // ROTATION_90
        floatArrayOf(1f, 0f, 1f, 1f, 0f, 0f, 0f, 1f), // ROTATION_180
        floatArrayOf(1f, 1f, 0f, 1f, 1f, 0f, 0f, 0f)  // ROTATION_270
    )

    @Volatile
    private var displayRotation: Int = Surface.ROTATION_0

    @Volatile
    private var currentTexCoords = texCoordsBackByRotation[Surface.ROTATION_0]

    @Volatile
    private var updateTexCoordBuffer = false

    override fun onSurfaceCreated(gl: GL10?, config: EGLConfig?) {
        GLES20.glClearColor(0f, 0f, 0f, 1f)

        shader = TiltShiftShader(context)
        shader.initialize()

        // Camera quad vertex buffer (crop-to-fill, recomputed when resolution is known)
        cameraVertexBuffer = allocateFloatBuffer(8)
        cameraVertexBuffer.put(floatArrayOf(-1f, -1f, 1f, -1f, -1f, 1f, 1f, 1f))
        cameraVertexBuffer.position(0)

        // Camera texcoord buffer (rotated for portrait)
        cameraTexCoordBuffer = allocateFloatBuffer(8)
        cameraTexCoordBuffer.put(currentTexCoords)
        cameraTexCoordBuffer.position(0)

        // Fullscreen quad for blur passes (standard coords)
        fullscreenVertexBuffer = allocateFloatBuffer(8)
        fullscreenVertexBuffer.put(floatArrayOf(-1f, -1f, 1f, -1f, -1f, 1f, 1f, 1f))
        fullscreenVertexBuffer.position(0)

        fullscreenTexCoordBuffer = allocateFloatBuffer(8)
        fullscreenTexCoordBuffer.put(floatArrayOf(0f, 0f, 1f, 0f, 0f, 1f, 1f, 1f))
        fullscreenTexCoordBuffer.position(0)

        // Create camera texture
        val textures = IntArray(1)
        GLES20.glGenTextures(1, textures, 0)
        cameraTextureId = textures[0]

        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, cameraTextureId)
        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR)
        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR)
        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE)
        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE)

        // Create SurfaceTexture for camera frames
        surfaceTexture = SurfaceTexture(cameraTextureId).also {
            it.setOnFrameAvailableListener { onFrameAvailable() }
            onSurfaceTextureAvailable(it)
        }
    }

    override fun onSurfaceChanged(gl: GL10?, width: Int, height: Int) {
        GLES20.glViewport(0, 0, width, height)
        surfaceWidth = width
        surfaceHeight = height
        vertexBufferDirty = true
        recreateFBOs(width, height)
    }

    override fun onDrawFrame(gl: GL10?) {
        surfaceTexture?.updateTexImage()

        if (vertexBufferDirty) {
            recomputeVertices()
            vertexBufferDirty = false
        }

        if (updateTexCoordBuffer) {
            cameraTexCoordBuffer.clear()
            cameraTexCoordBuffer.put(currentTexCoords)
            cameraTexCoordBuffer.position(0)
            updateTexCoordBuffer = false
        }

        val params = blurParameters

        // --- Pass 1: Camera → FBO-A (passthrough with crop-to-fill) ---
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, fboId)
        GLES20.glFramebufferTexture2D(
            GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0,
            GLES20.GL_TEXTURE_2D, fboTexA, 0
        )
        GLES20.glViewport(0, 0, surfaceWidth, surfaceHeight)
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT)
        shader.usePassthrough(cameraTextureId)
        drawQuad(
            shader.passthroughPositionLoc, shader.passthroughTexCoordLoc,
            cameraVertexBuffer, cameraTexCoordBuffer
        )

        // --- Pass 2: FBO-A → FBO-B (horizontal blur) ---
        GLES20.glFramebufferTexture2D(
            GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0,
            GLES20.GL_TEXTURE_2D, fboTexB, 0
        )
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT)
        shader.useBlurPass(fboTexA, params, surfaceWidth, surfaceHeight, 1f, 0f)
        drawQuad(
            shader.blurPositionLoc, shader.blurTexCoordLoc,
            fullscreenVertexBuffer, fullscreenTexCoordBuffer
        )

        // --- Pass 3: FBO-B → screen (vertical blur) ---
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0)
        GLES20.glViewport(0, 0, surfaceWidth, surfaceHeight)
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT)
        shader.useBlurPass(fboTexB, params, surfaceWidth, surfaceHeight, 0f, 1f)
        drawQuad(
            shader.blurPositionLoc, shader.blurTexCoordLoc,
            fullscreenVertexBuffer, fullscreenTexCoordBuffer
        )
    }

    fun updateParameters(params: BlurParameters) {
        blurParameters = params
    }

    fun setFrontCamera(front: Boolean) {
        if (isFrontCamera != front) {
            isFrontCamera = front
            refreshTexCoords()
        }
    }

    fun setCameraResolution(width: Int, height: Int) {
        if (cameraWidth != width || cameraHeight != height) {
            cameraWidth = width
            cameraHeight = height
            vertexBufferDirty = true
        }
    }

    /**
     * Updates the active display rotation. The texture-coordinate buffer is
     * rebuilt so the camera image stays world-aligned as the activity rotates
     * with the device under screenOrientation="fullSensor", and the
     * crop-to-fill math picks the correct effective aspect ratio.
     */
    fun setDisplayRotation(rotation: Int) {
        if (displayRotation != rotation) {
            displayRotation = rotation
            refreshTexCoords()
            vertexBufferDirty = true
        }
    }

    private fun refreshTexCoords() {
        val table = if (isFrontCamera) texCoordsFrontByRotation else texCoordsBackByRotation
        val idx = displayRotation.coerceIn(0, table.size - 1)
        currentTexCoords = table[idx]
        updateTexCoordBuffer = true
    }

    fun release() {
        shader.release()
        surfaceTexture?.release()
        surfaceTexture = null

        if (cameraTextureId != 0) {
            GLES20.glDeleteTextures(1, intArrayOf(cameraTextureId), 0)
            cameraTextureId = 0
        }

        deleteFBOs()
    }

    // --- Private helpers ---

    private fun drawQuad(
        positionLoc: Int,
        texCoordLoc: Int,
        vertices: FloatBuffer,
        texCoords: FloatBuffer
    ) {
        GLES20.glEnableVertexAttribArray(positionLoc)
        GLES20.glVertexAttribPointer(positionLoc, 2, GLES20.GL_FLOAT, false, 0, vertices)

        GLES20.glEnableVertexAttribArray(texCoordLoc)
        GLES20.glVertexAttribPointer(texCoordLoc, 2, GLES20.GL_FLOAT, false, 0, texCoords)

        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4)

        GLES20.glDisableVertexAttribArray(positionLoc)
        GLES20.glDisableVertexAttribArray(texCoordLoc)
    }

    /**
     * Recomputes camera vertex positions to achieve crop-to-fill.
     *
     * The camera sensor is landscape; after the orientation-dependent texcoord
     * rotation, the effective dimensions seen on screen are either swapped
     * (portrait orientations) or kept (landscape orientations). We scale the
     * vertex quad so the camera frame fills the surface without stretching —
     * the GPU clips the overflow.
     */
    private fun recomputeVertices() {
        var scaleX = 1f
        var scaleY = 1f

        if (cameraWidth > 0 && cameraHeight > 0 && surfaceWidth > 0 && surfaceHeight > 0) {
            val isPortrait = displayRotation == Surface.ROTATION_0 ||
                displayRotation == Surface.ROTATION_180
            val effectiveW = if (isPortrait) cameraHeight else cameraWidth
            val effectiveH = if (isPortrait) cameraWidth else cameraHeight
            val cameraRatio = effectiveW.toFloat() / effectiveH
            val screenRatio = surfaceWidth.toFloat() / surfaceHeight

            if (cameraRatio > screenRatio) {
                scaleX = cameraRatio / screenRatio
            } else {
                scaleY = screenRatio / cameraRatio
            }
        }

        cameraVertexBuffer.clear()
        cameraVertexBuffer.put(floatArrayOf(
            -scaleX, -scaleY,
             scaleX, -scaleY,
            -scaleX,  scaleY,
             scaleX,  scaleY
        ))
        cameraVertexBuffer.position(0)
    }

    private fun recreateFBOs(width: Int, height: Int) {
        deleteFBOs()

        // Create two color textures for ping-pong
        val texIds = IntArray(2)
        GLES20.glGenTextures(2, texIds, 0)
        fboTexA = texIds[0]
        fboTexB = texIds[1]

        for (texId in texIds) {
            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texId)
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR)
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR)
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE)
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE)
            GLES20.glTexImage2D(
                GLES20.GL_TEXTURE_2D, 0, GLES20.GL_RGBA,
                width, height, 0,
                GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, null
            )
        }

        // Create single FBO (we swap the attached texture for ping-pong)
        val fbos = IntArray(1)
        GLES20.glGenFramebuffers(1, fbos, 0)
        fboId = fbos[0]

        // Verify with texture A
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, fboId)
        GLES20.glFramebufferTexture2D(
            GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0,
            GLES20.GL_TEXTURE_2D, fboTexA, 0
        )
        val status = GLES20.glCheckFramebufferStatus(GLES20.GL_FRAMEBUFFER)
        if (status != GLES20.GL_FRAMEBUFFER_COMPLETE) {
            Log.e(TAG, "FBO incomplete: $status")
        }
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0)
    }

    private fun deleteFBOs() {
        if (fboId != 0) {
            GLES20.glDeleteFramebuffers(1, intArrayOf(fboId), 0)
            fboId = 0
        }
        if (fboTexA != 0 || fboTexB != 0) {
            GLES20.glDeleteTextures(2, intArrayOf(fboTexA, fboTexB), 0)
            fboTexA = 0
            fboTexB = 0
        }
    }

    private fun allocateFloatBuffer(floatCount: Int): FloatBuffer {
        return ByteBuffer.allocateDirect(floatCount * 4)
            .order(ByteOrder.nativeOrder())
            .asFloatBuffer()
    }
}