import {
  clamp,
  easeInOutCubic,
  easeOutBack,
  easeOutCubic,
  easeOutExpo,
  fadeEnvelope,
  hash01,
  lerp,
  progress,
} from "../easing.js";
import type { MotionFrameContext, MotionTemplate } from "../template.js";
import {
  el,
  escapeXml,
  fitText,
  fontStack,
  fullBackground,
  logoEl,
  num,
  stringParam,
  svgDocument,
  textEl,
  unit,
} from "../template.js";

const INTRO_PARAMS = [
  { name: "title", type: "string", required: false },
  { name: "tagline", type: "string", required: false },
] as const;

function title(ctx: MotionFrameContext): string {
  return stringParam(ctx, "title") ?? ctx.kit.name;
}

/** Fades the whole intro, background included, so it hands over to the video. */
function outro(t: number, ctx: MotionFrameContext): number {
  return fadeEnvelope(t, ctx.durationMs, 0, Math.min(400, ctx.durationMs * 0.15));
}

function tagline(ctx: MotionFrameContext, t: number, y: number, startPct: number): string {
  const text = stringParam(ctx, "tagline");
  if (!text) return "";
  const appear = easeOutCubic(
    progress(t, ctx.durationMs * startPct, ctx.durationMs * (startPct + 0.2)),
  );
  const fitted = fitText(text, ctx.width * 0.8, unit(ctx) * 0.055, unit(ctx) * 0.03);
  return textEl(fitted.text, {
    x: ctx.width / 2,
    y: y + (1 - appear) * unit(ctx) * 0.03,
    "text-anchor": "middle",
    "font-family": fontStack(ctx.fonts.body, "sans-serif"),
    "font-size": fitted.size,
    fill: ctx.kit.colors.text,
    opacity: appear,
  });
}

export const introLogoReveal: MotionTemplate = {
  info: {
    id: "intro_logo_reveal",
    kind: "intro",
    name: "Logo reveal",
    minDurationMs: 1500,
    maxDurationMs: 4000,
    params: [...INTRO_PARAMS],
  },
  frame(t, ctx) {
    const u = unit(ctx);
    const cx = ctx.width / 2;
    const cy = ctx.height * 0.46;
    const d = ctx.durationMs;
    const circle = easeOutExpo(progress(t, 0, d * 0.3));
    const pop = progress(t, d * 0.18, d * 0.48);
    const scale = pop <= 0 ? 0 : easeOutBack(pop);
    const radius = u * 0.24;
    let mark: string;
    if (ctx.logos.length > 0) {
      const size = radius * 1.3 * scale;
      mark = logoEl(ctx, { x: cx - size / 2, y: cy - size / 2, w: size, h: size });
    } else {
      const fitted = fitText(title(ctx), ctx.width * 0.8, u * 0.14, u * 0.05);
      mark = textEl(fitted.text, {
        x: cx,
        y: cy,
        "text-anchor": "middle",
        "dominant-baseline": "central",
        "font-family": fontStack(ctx.fonts.heading, "sans-serif"),
        "font-weight": 700,
        "font-size": fitted.size * Math.max(scale, 0.001),
        fill: ctx.kit.colors.text,
      });
    }
    const ring = el("circle", {
      cx,
      cy,
      r: Math.max(radius * circle, 0.01),
      fill: ctx.logos.length > 0 ? ctx.kit.colors.primary : "none",
      stroke: ctx.kit.colors.accent,
      "stroke-width": u * 0.01,
      opacity: ctx.logos.length > 0 ? 1 : 0.9,
    });
    const body = fullBackground(ctx) + ring + mark + tagline(ctx, t, cy + radius + u * 0.12, 0.42);
    return svgDocument(ctx, el("g", { opacity: outro(t, ctx) }, body));
  },
};

export const introKineticType: MotionTemplate = {
  info: {
    id: "intro_kinetic_type",
    kind: "intro",
    name: "Kinetic type",
    minDurationMs: 1500,
    maxDurationMs: 4000,
    params: [...INTRO_PARAMS],
  },
  frame(t, ctx) {
    const u = unit(ctx);
    const d = ctx.durationMs;
    const fitted = fitText(title(ctx), ctx.width * 0.86, u * 0.16, u * 0.05);
    const words = fitted.text.split(/\s+/).filter(Boolean).slice(0, 12);
    const stagger = (d * 0.35) / Math.max(words.length, 1);
    const baseY = ctx.height * 0.48;
    let previousOffset = 0;
    const spans = words.map((word, index) => {
      const appear = easeOutExpo(progress(t, index * stagger, index * stagger + d * 0.25));
      const offset = (1 - appear) * u * 0.18;
      const dy = offset - previousOffset;
      previousOffset = offset;
      const last = index === words.length - 1 && words.length > 1;
      return el(
        "tspan",
        {
          dy,
          fill: last ? ctx.kit.colors.primary : ctx.kit.colors.text,
          "fill-opacity": clamp(appear * 1.4),
        },
        escapeXml(index === words.length - 1 ? word : `${word} `),
      );
    });
    const heading = el(
      "text",
      {
        x: ctx.width / 2,
        y: baseY,
        "text-anchor": "middle",
        "font-family": fontStack(ctx.fonts.heading, "sans-serif"),
        "font-weight": 800,
        "font-size": fitted.size,
      },
      spans.join("") || " ",
    );
    const barGrow = easeInOutCubic(progress(t, d * 0.3, d * 0.6));
    const barWidth = ctx.width * 0.3 * barGrow;
    const bar = el("rect", {
      x: ctx.width / 2 - barWidth / 2,
      y: baseY + fitted.size * 0.3,
      width: barWidth,
      height: u * 0.012,
      fill: ctx.kit.colors.accent,
    });
    const body = fullBackground(ctx) + heading + bar + tagline(ctx, t, baseY + u * 0.16, 0.45);
    return svgDocument(ctx, el("g", { opacity: outro(t, ctx) }, body));
  },
};

/**
 * Glitch bursts are scheduled at a fixed 2 Hz. Photosensitivity guidance
 * (WCAG 2.3.1) allows at most three flashes per second; the template never
 * changes full-frame brightness, and the bursts stay below that rate even if
 * they were counted as flashes.
 */
export const GLITCH_BURST_INTERVAL_MS = 500;
const GLITCH_BURST_MS = 120;
const GLITCH_SLICES = 6;

export const introGlitch: MotionTemplate = {
  info: {
    id: "intro_glitch",
    kind: "intro",
    name: "Glitch",
    minDurationMs: 1500,
    maxDurationMs: 4000,
    params: [...INTRO_PARAMS],
  },
  frame(t, ctx) {
    const u = unit(ctx);
    const d = ctx.durationMs;
    const fitted = fitText(title(ctx).toUpperCase(), ctx.width * 0.84, u * 0.15, u * 0.05);
    const cy = ctx.height * 0.47;
    const burstIndex = Math.floor((t - 200) / GLITCH_BURST_INTERVAL_MS);
    const inBurst =
      t >= 200 && t - 200 - burstIndex * GLITCH_BURST_INTERVAL_MS < GLITCH_BURST_MS && t < d * 0.85;
    const reveal = easeOutCubic(progress(t, 0, d * 0.25));
    const textAttrs = {
      x: ctx.width / 2,
      y: cy,
      "text-anchor": "middle",
      "dominant-baseline": "central",
      "font-family": fontStack(ctx.fonts.heading, "sans-serif"),
      "font-weight": 900,
      "font-size": fitted.size,
    };
    const bandTop = cy - fitted.size * 0.7;
    const bandHeight = fitted.size * 1.4;
    const sliceHeight = bandHeight / GLITCH_SLICES;
    const defs = [
      el(
        "clipPath",
        { id: "reveal" },
        el("rect", { x: 0, y: 0, width: ctx.width * reveal, height: ctx.height }),
      ),
      ...Array.from({ length: GLITCH_SLICES }, (_, index) =>
        el(
          "clipPath",
          { id: `slice${index}` },
          el("rect", {
            x: 0,
            y: bandTop + index * sliceHeight,
            width: ctx.width,
            height: sliceHeight,
          }),
        ),
      ),
    ].join("");
    let title_: string;
    if (inBurst) {
      const split = u * 0.012;
      const ghosts =
        textEl(fitted.text, {
          ...textAttrs,
          x: ctx.width / 2 - split,
          fill: ctx.kit.colors.primary,
          opacity: 0.8,
        }) +
        textEl(fitted.text, {
          ...textAttrs,
          x: ctx.width / 2 + split,
          fill: ctx.kit.colors.accent,
          opacity: 0.8,
        });
      const slices = Array.from({ length: GLITCH_SLICES }, (_, index) => {
        const shift = (hash01(burstIndex, index) - 0.5) * u * 0.08;
        return el(
          "g",
          { "clip-path": `url(#slice${index})`, transform: `translate(${num(shift)} 0)` },
          textEl(fitted.text, { ...textAttrs, fill: ctx.kit.colors.text }),
        );
      }).join("");
      title_ = ghosts + slices;
    } else {
      title_ = textEl(fitted.text, { ...textAttrs, fill: ctx.kit.colors.text });
    }
    const scan = el("rect", {
      x: 0,
      y: lerp(bandTop, bandTop + bandHeight, (t % 900) / 900),
      width: ctx.width * reveal,
      height: u * 0.004,
      fill: ctx.kit.colors.accent,
      opacity: 0.6,
    });
    const body =
      fullBackground(ctx) +
      el("g", { "clip-path": "url(#reveal)" }, title_ + scan) +
      tagline(ctx, t, cy + fitted.size * 0.7 + u * 0.08, 0.4);
    return svgDocument(ctx, el("g", { opacity: outro(t, ctx) }, body), defs);
  },
};

export const introElegantFade: MotionTemplate = {
  info: {
    id: "intro_elegant_fade",
    kind: "intro",
    name: "Elegant fade",
    minDurationMs: 1500,
    maxDurationMs: 4000,
    params: [...INTRO_PARAMS],
  },
  frame(t, ctx) {
    const u = unit(ctx);
    const d = ctx.durationMs;
    const cy = ctx.height * 0.46;
    const line = easeInOutCubic(progress(t, 0, d * 0.4));
    const appear = easeOutCubic(progress(t, d * 0.15, d * 0.6));
    const spacing = lerp(0.4, 0.15, appear);
    const fitted = fitText(title(ctx), ctx.width * 0.8, u * 0.11, u * 0.04, spacing);
    const heading = textEl(fitted.text, {
      x: ctx.width / 2,
      y: cy - u * 0.03 + (1 - appear) * u * 0.02,
      "text-anchor": "middle",
      "font-family": fontStack(ctx.fonts.heading, "serif"),
      "font-weight": 400,
      "font-size": fitted.size,
      "letter-spacing": `${num(spacing)}em`,
      fill: ctx.kit.colors.text,
      opacity: appear,
    });
    const lineWidth = ctx.width * 0.4 * line;
    const rule = el("rect", {
      x: ctx.width / 2 - lineWidth / 2,
      y: cy + u * 0.02,
      width: lineWidth,
      height: Math.max(1, u * 0.003),
      fill: ctx.kit.colors.accent,
    });
    const body = fullBackground(ctx) + heading + rule + tagline(ctx, t, cy + u * 0.12, 0.5);
    return svgDocument(ctx, el("g", { opacity: outro(t, ctx) }, body));
  },
};