Initial external projectile type

src/projectiles.js

@@ -0,0 +1,79 @@
+import {H, PROJECTILE_ITERATIONS_PER_FRAME, PROJECTILE_ITERATION_PROGRESS, PROJECTILE_MAX_SOUND_FREQUENCY, PROJECTILE_MIN_SOUND_FREQUENCY, PROJECTILE_POWER_REDUCTION_FACTOR, PROJECTILE_WIND_REDUCTION_FACTOR, WEAPON_TYPES} from './constants.js';
+import {drawLineVirtual} from './gfx.js';
+import {isTank, createParticles} from './main.js';
+import {deg2rad, parable} from './math.js';
+import {audio, createOsc} from './sound.js';
+import {isTerrain} from './terrain.js';
+import {EXPLOSION_TYPES} from './weapons.js';
+
+
+export const PROJECTILE_TYPES = {
+  normal: {
+    create(spec, player, weapon, ox, oy, a, p, wind) {
+      const osc = createOsc('sine');
+      osc.start();
+
+      return {
+        type: 'normal',
+        player, weapon,
+        x:ox, y:oy, ox, oy, a, p,
+        t: 0, osc, wind,
+      };
+    },
+    stop(projectile) {
+      projectile.osc.stop(0);
+    },
+    update(projectile, terrain, trajectories, explosions) {
+      const prevProjectile = {...projectile};
+      const {weapon, player, wind} = projectile;
+      const weaponType = WEAPON_TYPES[weapon.type];
+      let exploded = false;
+
+      for (let i=0; i<PROJECTILE_ITERATIONS_PER_FRAME; i++) {
+        const {ox, oy, a, p, t} = projectile;
+
+        const [x, y] = parable(
+          t, ox, oy, deg2rad(180+a),
+          p / PROJECTILE_POWER_REDUCTION_FACTOR,
+          wind / PROJECTILE_WIND_REDUCTION_FACTOR,
+        );
+        projectile.x = x;
+        projectile.y = y;
+        projectile.t += PROJECTILE_ITERATION_PROGRESS;
+
+        const f = (
+          (1 - (1 / H * y)) *
+          (PROJECTILE_MAX_SOUND_FREQUENCY - PROJECTILE_MIN_SOUND_FREQUENCY) +
+          PROJECTILE_MIN_SOUND_FREQUENCY
+        );
+        projectile.osc.frequency.setValueAtTime(f, audio.currentTime);
+
+        if (
+          y > H ||
+          isTank(x, y) ||
+          isTerrain(terrain, x, y)
+        ) {
+          const explosionSpec = weaponType.explosion;
+          const explosionType = EXPLOSION_TYPES[explosionSpec.type];
+          explosions.push(explosionType.create(explosionSpec, x, y));
+          // @ts-ignore: canvas color hack
+          createParticles(x, y, p, terrain.color);
+          exploded = true;
+          break;
+        }
+      }
+
+      let trajectory = drawLineVirtual(
+        prevProjectile.x, prevProjectile.y,
+        projectile.x, projectile.y, player.c,
+      );
+
+      trajectory
+        .slice(0, trajectory.length-1) // Cut last pixel to prevent overlap
+        .map(x => ({...x, a:255}))     // Add alpha to all lines
+        .forEach(x => trajectories.push(x));
+
+      return !exploded;
+    },
+  }
+}