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 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.
 *
 * This renderer receives camera frames via SurfaceTexture and applies
 * the tilt-shift blur effect using GLSL shaders.
 */
class TiltShiftRenderer(
    private val context: Context,
    private val onSurfaceTextureAvailable: (SurfaceTexture) -> Unit,
    private val onFrameAvailable: () -> Unit
) : GLSurfaceView.Renderer {

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

    private lateinit var vertexBuffer: FloatBuffer
    private lateinit var texCoordBuffer: FloatBuffer

    private var surfaceWidth: Int = 0
    private var surfaceHeight: 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 rotated 90° for portrait mode (back camera)
    // (Camera sensors are landscape-oriented, we rotate to portrait)
    private val texCoordsBack = floatArrayOf(
        1f, 1f,  // Bottom left of screen  -> bottom right of texture
        1f, 0f,  // Bottom right of screen -> top right of texture
        0f, 1f,  // Top left of screen     -> bottom left of texture
        0f, 0f   // Top right of screen    -> top left of texture
    )

    // Texture coordinates for front camera (mirrored + rotated)
    // Front camera needs horizontal mirror for natural selfie view
    private val texCoordsFront = floatArrayOf(
        0f, 1f,  // Bottom left of screen
        0f, 0f,  // Bottom right of screen
        1f, 1f,  // Top left of screen
        1f, 0f   // Top right of screen
    )

    @Volatile
    private var currentTexCoords = texCoordsBack

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

        // Initialize shader
        shader = TiltShiftShader(context)
        shader.initialize()

        // Allocate vertex buffer (8 floats = 4 vertices × 2 components)
        vertexBuffer = ByteBuffer.allocateDirect(8 * 4)
            .order(ByteOrder.nativeOrder())
            .asFloatBuffer()
        // Fill with default full-screen quad; will be recomputed when camera resolution is known
        vertexBuffer.put(floatArrayOf(-1f, -1f, 1f, -1f, -1f, 1f, 1f, 1f))
        vertexBuffer.position(0)

        // Create texture coordinate buffer
        texCoordBuffer = ByteBuffer.allocateDirect(currentTexCoords.size * 4)
            .order(ByteOrder.nativeOrder())
            .asFloatBuffer()
            .put(currentTexCoords)
        texCoordBuffer.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
    }

    override fun onDrawFrame(gl: GL10?) {
        // Update texture with latest camera frame
        surfaceTexture?.updateTexImage()

        // Recompute vertex buffer for crop-to-fill when camera or surface dimensions change
        if (vertexBufferDirty) {
            recomputeVertices()
            vertexBufferDirty = false
        }

        // Update texture coordinate buffer if camera changed
        if (updateTexCoordBuffer) {
            texCoordBuffer.clear()
            texCoordBuffer.put(currentTexCoords)
            texCoordBuffer.position(0)
            updateTexCoordBuffer = false
        }

        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT)

        // Use shader and set parameters
        shader.use(cameraTextureId, blurParameters, surfaceWidth, surfaceHeight, isFrontCamera)

        // Set vertex positions
        GLES20.glEnableVertexAttribArray(shader.aPositionLocation)
        GLES20.glVertexAttribPointer(
            shader.aPositionLocation,
            2,
            GLES20.GL_FLOAT,
            false,
            0,
            vertexBuffer
        )

        // Set texture coordinates
        GLES20.glEnableVertexAttribArray(shader.aTexCoordLocation)
        GLES20.glVertexAttribPointer(
            shader.aTexCoordLocation,
            2,
            GLES20.GL_FLOAT,
            false,
            0,
            texCoordBuffer
        )

        // Draw quad
        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4)

        // Cleanup
        GLES20.glDisableVertexAttribArray(shader.aPositionLocation)
        GLES20.glDisableVertexAttribArray(shader.aTexCoordLocation)
    }

    /**
     * Updates blur parameters. Thread-safe.
     */
    fun updateParameters(params: BlurParameters) {
        blurParameters = params
    }

    /**
     * Sets whether using front camera. Updates texture coordinates accordingly.
     * Thread-safe - actual buffer update happens on next frame.
     */
    fun setFrontCamera(front: Boolean) {
        if (isFrontCamera != front) {
            isFrontCamera = front
            currentTexCoords = if (front) texCoordsFront else texCoordsBack
            // Buffer will be updated on next draw
            updateTexCoordBuffer = true
        }
    }

    @Volatile
    private var updateTexCoordBuffer = false

    /**
     * Sets the camera preview resolution for crop-to-fill aspect ratio correction.
     * Thread-safe — vertex buffer is recomputed on the next frame.
     */
    fun setCameraResolution(width: Int, height: Int) {
        if (cameraWidth != width || cameraHeight != height) {
            cameraWidth = width
            cameraHeight = height
            vertexBufferDirty = true
        }
    }

    /**
     * Recomputes vertex positions to achieve crop-to-fill.
     *
     * The camera sensor is landscape; after the 90° rotation applied via texture coordinates,
     * the effective portrait dimensions are (cameraHeight × cameraWidth). We scale the vertex
     * quad so the camera frame fills the screen 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) {
            // After 90° rotation: portrait width = cameraHeight, portrait height = cameraWidth
            val cameraRatio = cameraHeight.toFloat() / cameraWidth
            val screenRatio = surfaceWidth.toFloat() / surfaceHeight

            if (cameraRatio > screenRatio) {
                // Camera wider than screen → crop sides
                scaleX = cameraRatio / screenRatio
            } else {
                // Camera taller than screen → crop top/bottom
                scaleY = screenRatio / cameraRatio
            }
        }

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

    /**
     * Releases OpenGL resources.
     * Must be called from GL thread.
     */
    fun release() {
        shader.release()
        surfaceTexture?.release()
        surfaceTexture = null

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