// -*- coding: utf-8 -*-
//
// Copyright 2021-2023 Michael Büsch <m@bues.ch>
//
// Derived from https://github.com/mlochen/dungeon.git
// Copyright (C) 2020 Marco Lochen
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//

use crate::draw::Draw;
use crate::util::{degrees, radians};
use crate::vec2d::Vec2D;
use crate::wall::{VisibleWallsIter, Wall};
use crate::world::World;
use graphics::{Landscape3D, Point3D, Render3D, View3D};
use std::f32::{consts::FRAC_PI_2, EPSILON};

const EYE_LEVEL: f32 = 1.4; // 1.0 => wall top edge; 2.0 => wall hor. center line.

pub struct Render {
    world: World,
    sky_color: u32,
    image_height: f32,
    image_width: f32,
    image_height_half: f32,
    image_width_half: f32,
}

impl Render {
    pub fn new(world: World) -> Render {
        let mut self_ = Render {
            world,
            sky_color: 0,
            image_height: 0.0,
            image_width: 0.0,
            image_height_half: 0.0,
            image_width_half: 0.0,
        };
        self_.set_sky_color(0xFF007CB0);
        self_.set_fov_angle(86.0);
        self_
    }

    pub fn set_sky_color(&mut self, color: u32) {
        self.sky_color = color;
    }

    fn project_point(&self, point: Vec2D) -> Vec2D {
        let player = self.world.get_player();
        let player_pos = player.get_pos();
        let player_dir = player.get_dir();

        // Vector from player to point.
        let player_to_point = point - player_pos;
        let to_point_dir = player_to_point.normalized();

        // 1 -> point is right hand side of player fov center line.
        let rhs = if player_dir.phi_to_is_positive(&to_point_dir) {
            1.0
        } else {
            -1.0
        };

        // Angle diff on horizontal x/z plane from player view angle to point.
        let h_phi = player_dir.phi_to(&to_point_dir);

        // Z depth of the horizontal (x/z plane) fov triangle.
        let h_z_fov = self.image_width_half / (player.get_fov_phi() / 2.0).tan();

        // Get abs horiz. dist from player to point in view direction. (triangle in x/z plane)
        let h_z_pt = (player_to_point.len() * h_phi.cos()).abs();
        let v_fact = 1.0 / h_z_pt.max(EPSILON);

        // Calculate offsets from screen center point.
        let x_center_offs = h_z_fov * h_phi.tan() * rhs;
        let y_center_offs = h_z_fov * v_fact;

        // Calculate the projected coordinates.
        let lim = self.image_width.max(self.image_height) * 64.0;
        let x = (self.image_width_half + x_center_offs).clamp(-lim, lim);
        let y = (self.image_height_half + y_center_offs).clamp(-lim, lim);
        Vec2D::new(x, y)
    }

    fn corrected_wall_points(&self, wall: &Wall) -> (Vec2D, Vec2D) {
        let (p1, p2) = (wall.get_p1(), wall.get_p2());

        //TODO

        (p1, p2)
    }
}

impl View3D for Render {
    fn set_position(&mut self, pos: &Point3D) {
        self.world
            .get_player_mut()
            .set_pos(Vec2D::new(pos.x() * -1.0, pos.z()))
    }

    fn get_position(&self) -> Point3D {
        let player_pos = self.world.get_player().get_pos();
        Point3D::new(player_pos.x() * -1.0, 0.0, player_pos.y())
    }

    fn set_view_distance(&mut self, _view_dist: i32) {}

    fn get_view_distance(&self) -> i32 {
        i32::MAX
    }

    fn set_fov_angle(&mut self, fov_angle: f32) {
        self.world.get_player_mut().set_fov_phi(radians(fov_angle));
    }

    fn get_fov_angle(&self) -> f32 {
        degrees(self.world.get_player().get_fov_phi())
    }

    fn set_yaw_angle(&mut self, yaw_angle: f32) {
        self.world
            .get_player_mut()
            .set_phi(radians((yaw_angle * -1.0) + 90.0));
    }

    fn get_yaw_angle(&self) -> f32 {
        (degrees(self.world.get_player().get_phi()) * -1.0) - 90.0
    }

    fn set_roll_angle(&mut self, _roll_angle: f32) {}

    fn get_roll_angle(&self) -> f32 {
        0.0
    }

    fn set_pitch_angle(&mut self, _pitch_angle: f32) {}

    fn get_pitch_angle(&self) -> f32 {
        0.0
    }
}

impl Render3D for Render {
    fn render_scene(&mut self, render_buf: &mut [u32], image_width: usize, image_height: usize) {
        self.image_width = image_width as f32;
        self.image_height = image_height as f32;
        self.image_width_half = self.image_width / 2.0;
        self.image_height_half = self.image_height / 2.0;

        render_buf.fill(self.sky_color);
        let mut draw = Draw::new(render_buf, image_width, image_height);

        // Draw sky and ground.
        //TODO

        // Draw switches.
        //TODO

        // Draw walls and enemies.
        let player_dir = self.world.get_player().get_dir();
        let player_pos = self.world.get_player().get_pos();
        let walls =
            VisibleWallsIter::new(&self.world, self.world.get_player()).sorted_by_distance(false);
        for wall in walls {
            let (mut p1, mut p2) = (wall.get_p1(), wall.get_p2());
            let player_to_p1 = p1 - player_pos;
            let player_to_p2 = p2 - player_pos;
            let p1_phi = player_dir.phi_to(&player_to_p1);
            let p2_phi = player_dir.phi_to(&player_to_p2);
            if p1_phi > FRAC_PI_2 || p2_phi > FRAC_PI_2 {
                // > 90 deg
                // Wall is partially behind player. Correct the points.
                let res = self.corrected_wall_points(wall);
                p1 = res.0;
                p2 = res.1;
            }

            // Project the wall bottom points.
            let p1_proj = self.project_point(p1);
            let p2_proj = self.project_point(p2);

            // Calculate the top points.
            let a = p1_proj; // bottom
            let b = Vec2D::new(
                // top
                p1_proj.x(),
                p1_proj.y() - ((p1_proj.y() - self.image_height_half) * EYE_LEVEL),
            );
            let c = Vec2D::new(
                // top
                p2_proj.x(),
                p2_proj.y() - ((p2_proj.y() - self.image_height_half) * EYE_LEVEL),
            );
            let d = p2_proj; // bottom

            // Draw the wall tetragon.
            //TODO color
            draw.fill_tetragon((&a, &b, &c, &d), 0);
        }

        // Draw crosshair.
        //TODO

        // Draw health.
        //TODO

        // Draw ammo.
        //TODO

        // Draw overlay.
        //TODO
    }
}

impl Landscape3D for Render {
    fn get_terrain_height_at(&self, _point: Point3D) -> f32 {
        0.0
    }
}

// vim: ts=4 sw=4 expandtab