const Self = @This();
const rl = @import("raylib");
const std = @import("std");
const Gltf = @import("zgltf");
const GlobalContext = @import("./global-context.zig");
const EmulatorModel = @import("./emulator-model.zig");

const ChipContext = @import("chip.zig");
const RaylibChip = @import("raylib-chip.zig");

const assert = std.debug.assert;
const Allocator = std.mem.Allocator;
const StringList = std.ArrayList([]const u8);

ctx: *GlobalContext,
allocator: Allocator,

emulator: EmulatorModel,

camera_turn_vel: rl.Vector3 = rl.Vector3{ .x = 0, .y = 0, .z = 0 },
camera_target_orientation: ?rl.Vector3 = null,
previous_click_time: f64 = 0.0,

shader: rl.Shader,
lights: [2]Light,

chip: *ChipContext,
raylib_chip: *RaylibChip,
chip_sound: rl.Sound,

pub fn genSinWave(wave: *rl.Wave, frequency: f32) void {
    assert(wave.sampleSize == 16); // Only 16 bits are supported

    const sample_rate: f32 = @floatFromInt(wave.sampleRate);
    const sample_size: u5 = @truncate(wave.sampleSize);
    const max_sample_value: f32 = @floatFromInt(@shlExact(@as(u32, 1), sample_size - 1));

    const data: [*]i16 = @ptrCast(@alignCast(wave.data));
    for (0..wave.frameCount) |i| {
        const i_f32: f32 = @floatFromInt(i);
        const sin_value: f32 = @sin(std.math.pi*2*frequency/sample_rate*i_f32);
        data[i] = @intFromFloat(sin_value*max_sample_value);
    }
}

const Light = struct {
    const LightType = enum(i32) {
        DIRECTIONAL = 0,
        POINT = 1,
    };

    type: LightType,
    enabled: bool,
    position: rl.Vector3,
    target: rl.Vector3,
    color: rl.Color,
    attenuation: f32 = 0.0,

    enabledLoc: i32,
    typeLoc: i32,
    positionLoc: i32,
    targetLoc: i32,
    colorLoc: i32,
    attenuationLoc: i32 = 0,

    fn getLightShaderLocation(shader: rl.Shader, idx: usize, comptime name: []const u8) i32 {
        var buf: [128]u8 = undefined;
        var fba = std.heap.FixedBufferAllocator.init(&buf);
        const prop_name = std.fmt.allocPrintZ(fba.allocator(), "lights[{d}]." ++ name, .{idx}) catch unreachable;
        return rl.GetShaderLocation(shader, prop_name);
    }

    pub fn init(idx: usize, light_type: LightType, postion: rl.Vector3, target: rl.Vector3, color: rl.Color, shader: rl.Shader) Light {
        var light = Light{
            .type = light_type,
            .enabled = true,
            .position = postion,
            .target = target,
            .color = color,
            .enabledLoc = Light.getLightShaderLocation(shader, idx, "enabled"),
            .typeLoc = Light.getLightShaderLocation(shader, idx, "type"),
            .positionLoc = Light.getLightShaderLocation(shader, idx, "position"),
            .targetLoc = Light.getLightShaderLocation(shader, idx, "target"),
            .colorLoc = Light.getLightShaderLocation(shader, idx, "color"),
        };
        light.update_values(shader);
        return light;
    }

    pub fn update_values(self: *Light, shader: rl.Shader) void {
        const enabled: i32 = @intFromBool(self.enabled);
        rl.SetShaderValue(shader, self.enabledLoc, &enabled, rl.ShaderUniformDataType.SHADER_UNIFORM_INT);

        const lightType: i32 = @intFromEnum(self.type);
        rl.SetShaderValue(shader, self.typeLoc, &lightType, rl.ShaderUniformDataType.SHADER_UNIFORM_INT);

        const position = [3]f32{ self.position.x, self.position.y, self.position.z };
        rl.SetShaderValue(shader, self.positionLoc, &position, rl.ShaderUniformDataType.SHADER_UNIFORM_VEC3);

        const target = [3]f32{ self.target.x, self.target.y, self.target.z };
        rl.SetShaderValue(shader, self.targetLoc, &target, rl.ShaderUniformDataType.SHADER_UNIFORM_VEC3);

        const color = [4]f32{
            @as(f32, @floatFromInt(self.color.r)) / 255.0,
            @as(f32, @floatFromInt(self.color.g)) / 255.0,
            @as(f32, @floatFromInt(self.color.b)) / 255.0,
            @as(f32, @floatFromInt(self.color.a)) / 255.0,
        };
        rl.SetShaderValue(shader, self.colorLoc, &color, rl.ShaderUniformDataType.SHADER_UNIFORM_VEC4);
    }
};

fn getCameraProjection(camera: *const rl.Camera3D) rl.Matrix {
    const screen_width: f32 = @floatFromInt(rl.GetScreenWidth());
    const screen_height: f32 = @floatFromInt(rl.GetScreenHeight());

    if (camera.projection == .CAMERA_PERSPECTIVE) {
        return rl.MatrixPerspective(camera.fovy*rl.DEG2RAD, screen_width/screen_height, rl.RL_CULL_DISTANCE_NEAR, rl.RL_CULL_DISTANCE_FAR);
    } else if (camera.projection == .CAMERA_ORTHOGRAPHIC) {
        const aspect = screen_width/screen_height;
        const top = camera.fovy/2.0;
        const right = top*aspect;

        return rl.MatrixOrtho(-right, right, -top, top, rl.RL_CULL_DISTANCE_NEAR, rl.RL_CULL_DISTANCE_FAR);
    } else {
        unreachable;
    }
}

fn getScreenDirectionFromCamera(mat_proj: *const rl.Matrix, mat_view: *const rl.Matrix, point: rl.Vector2) rl.Vector3 {
    const screen_width: f32 = @floatFromInt(rl.GetScreenWidth());
    const screen_height: f32 = @floatFromInt(rl.GetScreenHeight());

    const ndc_x = (2.0*point.x) / screen_width - 1.0;
    const ndc_y = 1.0 - (2.0*point.y) / screen_height;

    var near_point = rl.Vector3Unproject(.{ .x = ndc_x, .y = ndc_y, .z = 0.0 }, mat_proj.*, mat_view.*);
    var far_point  = rl.Vector3Unproject(.{ .x = ndc_x, .y = ndc_y, .z = 1.0 }, mat_proj.*, mat_view.*);

    return rl.Vector3Subtract(far_point, near_point).normalize();
}

fn getPrefferedDistanceToBox(camera: *const rl.Camera3D, box: rl.BoundingBox) f32 {
    const screen_width: f32 = @floatFromInt(rl.GetScreenWidth());
    const screen_height: f32 = @floatFromInt(rl.GetScreenHeight());
    const margin = @min(screen_width, screen_height)*0.1;

    const box_size = box.max.sub(box.min);

    const max_model_scale = @min((screen_width-2*margin)/box_size.x, (screen_height-2*margin)/box_size.y);
    // const model_screen_width = box_size.x * max_model_scale;
    const model_screen_height = box_size.y * max_model_scale;

    const mat_proj = getCameraProjection(camera);
    const mat_view = rl.MatrixIdentity(); // rl.MatrixLookAt(camera.position, camera.target, camera.up);

    const screen_middle = rl.Vector2{ .x = screen_width/2, .y = screen_height/2 };
    const box_top_middle = screen_middle.add(.{ .y = -model_screen_height/2 });

    const middle_dir = getScreenDirectionFromCamera(&mat_proj, &mat_view, screen_middle);
    const top_middle_dir = getScreenDirectionFromCamera(&mat_proj, &mat_view, box_top_middle);
    const angle = top_middle_dir.angleBetween(middle_dir);
    const distance = 1/@tan(angle) * (box_size.y/2) + box_size.z/4;
    return distance;
}

pub fn init(allocator: Allocator, ctx: *GlobalContext) !Self {
    const shader = rl.LoadShader("src/shaders/main.vs", "src/shaders/main.fs");
    shader.locs.?[@intFromEnum(rl.ShaderLocationIndex.SHADER_LOC_VECTOR_VIEW)] = rl.GetShaderLocation(shader, "viewPos");

    const ambientLoc = rl.GetShaderLocation(shader, "ambient");
    rl.SetShaderValue(shader, ambientLoc, &[4]f32{ 0.6, 0.6, 1, 1.0 }, .SHADER_UNIFORM_VEC4);

    var light1 = Light.init(0, .DIRECTIONAL, rl.Vector3.new(0.2, 0, -0.2), rl.Vector3.zero(), rl.WHITE, shader);
    var light2 = Light.init(1, .DIRECTIONAL, rl.Vector3.new(0.2, 0, 0.2), rl.Vector3.zero(), rl.WHITE, shader);

    var chip = try allocator.create(ChipContext);
    chip.* = try ChipContext.init(allocator);

    const sample_rate = 44100;
    var data = try allocator.alloc(i16, sample_rate);
    defer allocator.free(data);
    var chip_wave = rl.Wave{
        .frameCount = sample_rate,
        .sampleRate = sample_rate,
        .sampleSize = 16,
        .channels = 1,
        .data = @ptrCast(data.ptr),
    };

    genSinWave(&chip_wave, 440);
    var chip_sound = rl.LoadSoundFromWave(chip_wave);
    rl.SetSoundVolume(chip_sound, 0.2);

    var raylib_chip = try allocator.create(RaylibChip);
    raylib_chip.* = RaylibChip.init(chip, chip_sound);

    var emulator = try EmulatorModel.init(allocator, raylib_chip);
    emulator.setShader(shader);

    return Self {
        .allocator = allocator,
        .ctx = ctx,
        .emulator = emulator,
        .shader = shader,
        .lights = .{light1, light2},

        .chip = chip,
        .raylib_chip = raylib_chip,
        .chip_sound = chip_sound,
    };
}

pub fn deinit(self: *Self) void {
    self.emulator.deinit();
    rl.UnloadSound(self.chip_sound);
    self.chip.deinit();
    self.allocator.destroy(self.raylib_chip);
    self.allocator.destroy(self.chip);
}

fn updateCamera(self: *Self, dt: f32) void {
    const mouse_delta = rl.GetMouseDelta();
    const camera = &self.ctx.camera;
    const emulator = &self.emulator;

    if (rl.IsWindowResized()) {
        const distance = getPrefferedDistanceToBox(camera, emulator.bbox);
        const direction = camera.position.sub(emulator.position).normalize();
        camera.position = emulator.position.add(direction.scale(distance));
    }

    if (rl.Vector3Equals(camera.position, rl.Vector3Zero()) == 1) {
        const distance = getPrefferedDistanceToBox(camera, self.emulator.bbox);
        camera.target = emulator.position;
        camera.position = emulator.position.sub(rl.Vector3.new(0, 0, 1).scale(distance));
    }

    var camera_turn_acc = rl.Vector3Zero();
    if (rl.IsMouseButtonDown(rl.MouseButton.MOUSE_BUTTON_LEFT)) {
        if (@fabs(mouse_delta.x) > 5) {
            const rotation_speed = 2; // Radians/second
            camera_turn_acc.x = -rotation_speed*mouse_delta.x;
        }
        if (@fabs(mouse_delta.x) < 5) {
            self.camera_turn_vel = self.camera_turn_vel.scale(0.90); // Holding drag
        }
    }

    if (rl.IsMouseButtonPressed(rl.MouseButton.MOUSE_BUTTON_LEFT)) {
        self.camera_target_orientation = null;

        const now = rl.GetTime();
        const duration_between_clicks = now - self.previous_click_time;
        if (duration_between_clicks < 0.3) {
            const ray = rl.GetMouseRay(rl.GetMousePosition(), camera.*);
            const collision = rl.GetRayCollisionBox(ray, self.emulator.bbox);
            if (collision.hit) {
                const front_face_normal = rl.Vector3.new(0, 0, -1);
                const back_face_normal = rl.Vector3.new(0, 0, 1);
                if (rl.Vector3Equals(collision.normal, front_face_normal) == 1) {
                    self.camera_target_orientation = front_face_normal;
                } else if (rl.Vector3Equals(collision.normal, back_face_normal) == 1) {
                    self.camera_target_orientation = back_face_normal;
                }
            }
        }
        self.previous_click_time = now;
    }

    if (self.camera_target_orientation) |target| {
        const current_direction = camera.position.sub(emulator.position).normalize();
        const current_angle = std.math.atan2(f32, current_direction.z, current_direction.x);
        const target_angle = std.math.atan2(f32, target.z, target.x);
        const diff_angle = std.math.pi - @mod((target_angle - current_angle) + 3*std.math.pi, 2*std.math.pi);
        if (@fabs(diff_angle) < 0.001) {
            self.camera_turn_vel.x = 0;
            self.camera_target_orientation = null;
        } else {
            self.camera_turn_vel.x = diff_angle*3;
        }
    }

    self.camera_turn_vel = self.camera_turn_vel.scale(0.95); // Ambient drag
    self.camera_turn_vel = self.camera_turn_vel.add(camera_turn_acc.scale(dt));

    const camera_min_vel = 0;
    if (self.camera_turn_vel.length() > camera_min_vel) {
        const rotation = rl.MatrixRotate(camera.up.normalize(), self.camera_turn_vel.x*dt);
        var view = rl.Vector3Subtract(camera.position, camera.target);
        view = rl.Vector3Transform(view, rotation);
        camera.position = rl.Vector3Add(camera.target, view);
    }
}

pub fn update(self: *Self, dt: f32) void {
    self.updateCamera(dt);

    const camera = &self.ctx.camera;
    const cameraPos = [3]f32{ camera.position.x, camera.position.y, camera.position.z };
    rl.SetShaderValue(self.shader, self.shader.locs.?[@intFromEnum(rl.ShaderLocationIndex.SHADER_LOC_VECTOR_VIEW)], &cameraPos, rl.ShaderUniformDataType.SHADER_UNIFORM_VEC3);
    for (&self.lights) |*light| {
        light.update_values(self.shader);
    }

    self.emulator.updateDisplay();

    // {
    //     var matProj = rl.MatrixIdentity();
    //     // projection = CAMERA_PERSPECTIVE
    //     matProj = rl.MatrixPerspective(camera.fovy*rl.DEG2RAD, (screen_width/screen_height), rl.RL_CULL_DISTANCE_NEAR, rl.RL_CULL_DISTANCE_FAR);
    //
    //     var matView = rl.MatrixLookAt(camera.position, camera.target, camera.up);
    //     // Convert world position vector to quaternion
    //     var worldPos = rl.Vector4{ .x = position.x, .y = position.y, .z = position.z, .w = 1.0 };
    //
    //     std.debug.print("worldPos {}\n", .{worldPos});
    //     // Transform world position to view
    //     worldPos = rl.QuaternionTransform(worldPos, matView);
    //
    //     // Transform result to projection (clip space position)
    //     worldPos = rl.QuaternionTransform(worldPos, matProj);
    //
    //     // Calculate normalized device coordinates (inverted y)
    //     var ndcPos = rl.Vector3.new( worldPos.x/worldPos.w, -worldPos.y/worldPos.w, worldPos.z/worldPos.w );
    //
    //     // Calculate 2d screen position vector
    //     screen_position = rl.Vector2{ .x = (ndcPos.x + 1.0)/2.0*screen_width, .y = (ndcPos.y + 1.0)/2.0*screen_height };
    // }

    // const target_screen_position = rl.Vector2{ .x = screen_width/2, .y = screen_height*0.1 };
    // {
    //     var matProj = get_camera_projection(&camera);
    //     var matView = rl.MatrixLookAt(camera.position, camera.target, camera.up);
    //
    //     const ndc_x = (2.0*target_screen_position.x) / screen_width - 1.0;
    //     const ndc_y = 1.0 - (2.0*target_screen_position.y) / screen_height;
    //
    //     var near_point = rl.Vector3Unproject(.{ .x = ndc_x, .y = ndc_y, .z = 0.0 }, matProj, matView);
    //     var far_point  = rl.Vector3Unproject(.{ .x = ndc_x, .y = ndc_y, .z = 1.0 }, matProj, matView);
    //
    //     var direction = rl.Vector3Subtract(far_point, near_point).normalize();
    //
    //     var origin: rl.Vector3 = undefined;
    //     if (camera.projection == .CAMERA_PERSPECTIVE) {
    //         origin = camera.position;
    //     } else {
    //         origin = rl.Vector3Unproject(.{ .x = ndc_x, .y = ndc_y, .z = -1.0 }, matProj, matView);
    //     }
    //
    //     var world_pos = origin.add(direction.scale(3));
    //
    //     model_position = world_pos;
    // }
}

pub fn draw(self: *Self) void {
    rl.BeginShaderMode(self.shader);
    {
        self.emulator.draw();
    }
    rl.EndShaderMode();
}