src/lib/editor/validation.ts

/**
 * Subtitle validation — CPL, CPS, overlap, min duration checks.
 */

import type { SubtitleData } from "./event-bus";

export interface ValidationIssue {
  type: "cpl" | "cps" | "overlap" | "min_duration" | "gap";
  severity: "error" | "warning";
  message: string;
  value?: number;
  limit?: number;
}

export interface ValidationConfig {
  maxCPL: number;       // Max characters per line (default 42)
  maxCPS: number;       // Max characters per second (default 25)
  minDurationMs: number; // Min subtitle duration in ms (default 833 = 20 frames at 24fps)
  minGapMs: number;     // Min gap between subtitles in ms (default 83 = 2 frames at 24fps)
}

export const DEFAULT_VALIDATION: ValidationConfig = {
  maxCPL: 42,
  maxCPS: 25,
  minDurationMs: 833,
  minGapMs: 83,
};

/** Parse a timecode string (HH:MM:SS:FF or HH:MM:SS.mmm) to milliseconds */
export function tcToMs(tc: string, fps: number = 23.976): number {
  if (!tc) return 0;

  // Handle HH:MM:SS:FF (frame-based)
  const frameParts = tc.match(/^(\d{2}):(\d{2}):(\d{2}):(\d{2})$/);
  if (frameParts) {
    const h = parseInt(frameParts[1]);
    const m = parseInt(frameParts[2]);
    const s = parseInt(frameParts[3]);
    const f = parseInt(frameParts[4]);
    return Math.round((h * 3600 + m * 60 + s) * 1000 + (f / fps) * 1000);
  }

  // Handle HH:MM:SS.mmm (millisecond-based, SRT style)
  const msParts = tc.match(/^(\d{2}):(\d{2}):(\d{2})[.,](\d{3})$/);
  if (msParts) {
    const h = parseInt(msParts[1]);
    const m = parseInt(msParts[2]);
    const s = parseInt(msParts[3]);
    const ms = parseInt(msParts[4]);
    return h * 3600000 + m * 60000 + s * 1000 + ms;
  }

  return 0;
}

/** Get the longest line length in a subtitle text */
export function getMaxLineLength(text: string): number {
  return Math.max(...text.split("\n").map((line) => line.length));
}

/** Get total visible character count (excluding tags) */
export function getCharCount(text: string): number {
  // Strip basic formatting tags
  return text
    .replace(/<[^>]+>/g, "")
    .replace(/\{[^}]+\}/g, "")
    .replace(/\n/g, "")
    .length;
}

/** Validate a single subtitle */
export function validateSubtitle(
  sub: SubtitleData,
  index: number,
  allSubs: SubtitleData[],
  config: ValidationConfig = DEFAULT_VALIDATION,
  fps: number = 23.976
): ValidationIssue[] {
  const issues: ValidationIssue[] = [];

  // CPL check
  const maxLine = getMaxLineLength(sub.text);
  if (maxLine > config.maxCPL) {
    issues.push({
      type: "cpl",
      severity: "error",
      message: `CPL ${maxLine}/${config.maxCPL}`,
      value: maxLine,
      limit: config.maxCPL,
    });
  }

  // CPS check
  const durationMs = tcToMs(sub.tcOut, fps) - tcToMs(sub.tcIn, fps);
  if (durationMs > 0) {
    const charCount = getCharCount(sub.text);
    const cps = charCount / (durationMs / 1000);
    if (cps > config.maxCPS) {
      issues.push({
        type: "cps",
        severity: "warning",
        message: `CPS ${cps.toFixed(1)}/${config.maxCPS}`,
        value: Math.round(cps * 10) / 10,
        limit: config.maxCPS,
      });
    }
  }

  // Min duration check
  if (durationMs > 0 && durationMs < config.minDurationMs) {
    issues.push({
      type: "min_duration",
      severity: "warning",
      message: `Duration ${durationMs}ms < ${config.minDurationMs}ms`,
      value: durationMs,
      limit: config.minDurationMs,
    });
  }

  // Overlap with next subtitle
  if (index < allSubs.length - 1) {
    const nextSub = allSubs[index + 1];
    const tcOut = tcToMs(sub.tcOut, fps);
    const nextTcIn = tcToMs(nextSub.tcIn, fps);
    if (tcOut > nextTcIn) {
      issues.push({
        type: "overlap",
        severity: "error",
        message: `Overlaps next subtitle by ${tcOut - nextTcIn}ms`,
        value: tcOut - nextTcIn,
      });
    } else if (nextTcIn - tcOut < config.minGapMs && nextTcIn - tcOut > 0) {
      issues.push({
        type: "gap",
        severity: "warning",
        message: `Gap ${nextTcIn - tcOut}ms < ${config.minGapMs}ms`,
        value: nextTcIn - tcOut,
        limit: config.minGapMs,
      });
    }
  }

  return issues;
}