/**
 * Pure phase-id parsing/matching helpers — normalize, token match,
 * milestone/phase-dir id parsing, phase-markdown regex builders.
 *
 * Extracted from core.cts (ADR-857 rollout phase 2a / issue #865).
 * The hand-written bodies are preserved byte-for-behaviour; only the module
 * boundary moved. The core.cjs re-export spine was retired in epic #1267;
 * callers import phase-id helpers from phase-id.cjs directly.
 *
 * Dependencies: none (pure string/regex, no Node built-ins required).
 */

// ─── Phase-id helpers ─────────────────────────────────────────────────────────

function escapeRegex(value: unknown): string {
  return String(value).replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
}

// project_code values start with an uppercase letter (e.g. PROJ, APP_CODE);
// leading underscores are not valid project codes per .planning/config.json.
const PROJECT_CODE_PREFIX_STRIP_RE = /^[A-Z][A-Z0-9_]*-(?=\d)/;
const PROJECT_CODE_PREFIX_STRIP_RE_I = /^[A-Z][A-Z0-9_]*-(?=\d)/i;
const PROJECT_CODE_PREFIX_CAPTURE_RE_I = /^([A-Z][A-Z0-9_]*)-(\d.*)/i;
const OPTIONAL_PROJECT_CODE_PREFIX_SOURCE = '(?:[A-Z][A-Z0-9_]*-)?';

// #1729: phase headers may carry a parenthetical tag between the number and the
// colon, e.g. `### Phase 26 (Cluster B): Title`. This optional, non-capturing
// fragment is injected at every phase-header regex call site (immediately after
// the phase-number token, before the colon/space delimiter) so the resolver
// tolerates the tag — mirroring how `[...]` is already tolerated before `Phase`.
// `[^)\n]*` keeps the match single-line (headers are one line) to avoid
// over-consuming across a malformed multi-line document. Injected at the call
// site (not baked into phaseMarkdownRegexSource) so it applies uniformly to
// both the numeric and project-code-exact escaped sources, and so the decimal
// sub-phase patterns can place it after the `.N` segment.
//
// Enumeration/parse call sites that read phase headers from a regex *literal*
// (rather than a `new RegExp` built from an interpolated phase number) cannot
// reference this constant; they inline its literal-regex mirror instead —
// `(?:\s*\([^)\n]*\))?` — kept character-for-character equivalent to this
// source. Both forms must change together; see the #1729 regression test.
const OPTIONAL_PHASE_TAG_SOURCE = '(?:\\s*\\([^)\\n]*\\))?';

function stripProjectCodePrefix(value: unknown, caseInsensitive = true): string {
  const input = String(value);
  const re = caseInsensitive ? PROJECT_CODE_PREFIX_STRIP_RE_I : PROJECT_CODE_PREFIX_STRIP_RE;
  return input.replace(re, '');
}

function hasProjectCodePrefix(value: unknown): boolean {
  return PROJECT_CODE_PREFIX_STRIP_RE_I.test(String(value));
}

function normalizePhaseName(phase: unknown): string {
  const str = String(phase);
  // Strip optional project_code prefix (e.g., 'CK-01' → '01')
  const stripped = stripProjectCodePrefix(str, false);
  // Milestone-prefixed phase IDs: M-NN or M-N-N (deep decomposition).
  const milestoneMatch = stripped.match(/^(\d+)((?:-\d+)+)([A-Z]?(?:\.\d+)*)$/i);
  if (milestoneMatch) {
    const major = milestoneMatch[1].padStart(2, '0');
    const subSegments = milestoneMatch[2].slice(1).split('-').map(s => s.padStart(2, '0'));
    const suffix = milestoneMatch[3] || '';
    return `${major}-${subSegments.join('-')}${suffix}`;
  }
  // Standard numeric phases: 1, 01, 12A, 12.1
  const match = stripped.match(/^(\d+)([A-Z])?((?:\.\d+)*)/i);
  if (match) {
    const padded = match[1].padStart(2, '0');
    // Preserve original case of letter suffix (#1962).
    const letter = match[2] || '';
    const decimal = match[3] || '';
    return padded + letter + decimal;
  }
  // Custom phase IDs (e.g. PROJ-42, AUTH-101): return as-is
  return str;
}

function getMilestoneFromPhaseId(phaseId: unknown): string | null {
  const stripped = stripProjectCodePrefix(phaseId);
  const m = stripped.match(/^0*(\d+)-\d/);
  if (!m) return null;
  const major = parseInt(m[1], 10);
  if (major === 0 || major === 999) return null;
  return `v${major}.0`;
}

function getPhaseDirFromPhaseId(phaseId: unknown, phaseName: string | null | undefined, projectCode: string | null | undefined): string | null {
  const stripped = stripProjectCodePrefix(phaseId);
  const m = stripped.match(/^0*(\d+)-(0*(\d+(?:-\d+)*))$/);
  if (!m) return null;
  const milestone = String(parseInt(m[1], 10)).padStart(2, '0');
  const subParts = m[2].split('-').map(p => String(parseInt(p, 10)).padStart(2, '0'));
  const sub = subParts.join('-');
  const slug = phaseName
    ? phaseName.toLowerCase().replace(/[^a-z0-9]+/g, '-').replace(/^-+|-+$/g, '')
    : '';
  const parts = [milestone, sub, slug].filter(Boolean);
  const base = parts.join('-');
  return projectCode ? `${projectCode}-${base}` : base;
}

/**
 * Render a regex source fragment matching a phase number against ROADMAP/STATE
 * prose regardless of zero-padding on either side.
 */
function phaseMarkdownRegexSource(phaseNum: unknown): string {
  const stripped = stripProjectCodePrefix(phaseNum);

  // Milestone-prefixed IDs: M-NN or M-N-N (deep).
  const milestoneSegments = stripped.match(/^(\d+)((?:-\d+)*)([A-Z]?(?:\.\d+)*)$/i);
  if (milestoneSegments && milestoneSegments[2]) {
    const majorUnpadded = milestoneSegments[1].replace(/^0+/, '') || '0';
    const subParts = milestoneSegments[2].slice(1).split('-');
    const subFragments = subParts.map(s => {
      const unpadded = s.replace(/^0+/, '') || '0';
      return `0*${escapeRegex(unpadded)}`;
    });
    const suffix = milestoneSegments[3] || '';
    const suffixFragment = suffix ? escapeRegex(suffix) : '';
    return `0*${escapeRegex(majorUnpadded)}-${subFragments.join('-')}${suffixFragment}`;
  }

  // Plain numeric phase: 1, 01, 12A, 12.1
  const match = stripped.match(/^0*(\d+)([A-Z])?((?:\.\d+)*)$/i);
  if (!match) return escapeRegex(phaseNum);

  const integer = match[1].replace(/^0+/, '') || '0';
  const letter = match[2] ? escapeRegex(match[2]) : '';
  const decimal = match[3] ? escapeRegex(match[3]) : '';
  return `0*${escapeRegex(integer)}${letter}${decimal}`;
}

/**
 * #3599: when the caller passed a project-code-prefixed ID like `PROJ-42`,
 * return the exact-escaped form.
 */
function phaseMarkdownRegexSourceExact(phaseNum: unknown): string | null {
  const raw = String(phaseNum);
  if (!hasProjectCodePrefix(raw)) return null;
  return escapeRegex(raw);
}

function comparePhaseNum(a: unknown, b: unknown): number {
  // Strip optional project_code prefix before comparing
  const sa = stripProjectCodePrefix(a);
  const sb = stripProjectCodePrefix(b);

  const milestoneA = sa.match(/^(\d+)((?:-\d+)+)([A-Z]?(?:\.\d+)*)$/i);
  const milestoneB = sb.match(/^(\d+)((?:-\d+)+)([A-Z]?(?:\.\d+)*)$/i);

  if (milestoneA && milestoneB) {
    const segsA = [parseInt(milestoneA[1], 10), ...milestoneA[2].slice(1).split('-').map(s => parseInt(s, 10))];
    const segsB = [parseInt(milestoneB[1], 10), ...milestoneB[2].slice(1).split('-').map(s => parseInt(s, 10))];
    const maxSegs = Math.max(segsA.length, segsB.length);
    for (let i = 0; i < maxSegs; i++) {
      const av = segsA[i] !== undefined ? segsA[i] : 0;
      const bv = segsB[i] !== undefined ? segsB[i] : 0;
      if (av !== bv) return av - bv;
    }
    const sufA = milestoneA[3] || '';
    const sufB = milestoneB[3] || '';
    if (sufA !== sufB) return sufA < sufB ? -1 : 1;
    return 0;
  }

  if (milestoneA || milestoneB) return String(a).localeCompare(String(b));

  const pa = sa.match(/^(\d+)([A-Z])?((?:\.\d+)*)/i);
  const pb = sb.match(/^(\d+)([A-Z])?((?:\.\d+)*)/i);
  if (!pa || !pb) return String(a).localeCompare(String(b));
  const intDiff = parseInt(pa[1], 10) - parseInt(pb[1], 10);
  if (intDiff !== 0) return intDiff;
  const la = (pa[2] || '').toUpperCase();
  const lb = (pb[2] || '').toUpperCase();
  if (la !== lb) {
    if (!la) return -1;
    if (!lb) return 1;
    return la < lb ? -1 : 1;
  }
  const aDecParts = pa[3] ? pa[3].slice(1).split('.').map(p => parseInt(p, 10)) : [];
  const bDecParts = pb[3] ? pb[3].slice(1).split('.').map(p => parseInt(p, 10)) : [];
  const maxLen = Math.max(aDecParts.length, bDecParts.length);
  if (aDecParts.length === 0 && bDecParts.length > 0) return -1;
  if (bDecParts.length === 0 && aDecParts.length > 0) return 1;
  for (let i = 0; i < maxLen; i++) {
    const av = Number.isFinite(aDecParts[i]) ? aDecParts[i] : 0;
    const bv = Number.isFinite(bDecParts[i]) ? bDecParts[i] : 0;
    if (av !== bv) return av - bv;
  }
  return 0;
}

/**
 * Extract the phase token from a directory name.
 */
function extractPhaseToken(dirName: string): string {
  const codePrefixMatch = dirName.match(PROJECT_CODE_PREFIX_CAPTURE_RE_I);
  let prefix = '';
  let rest = dirName;
  if (codePrefixMatch) {
    prefix = codePrefixMatch[1] + '-';
    rest = codePrefixMatch[2];
  }

  const segments = rest.split('-');
  const tokenSegments: string[] = [];
  for (let i = 0; i < segments.length; i++) {
    const seg = segments[i];
    if (/^\d/.test(seg) || (i === 0 && /^[A-Za-z]{1,3}\d/.test(seg))) {
      tokenSegments.push(seg);
    } else {
      break;
    }
  }

  if (tokenSegments.length === 0) {
    return dirName;
  }

  return prefix + tokenSegments.join('-');
}

/**
 * Check if a directory name's phase token matches the normalized phase exactly.
 */
function phaseTokenMatches(dirName: string, normalized: string): boolean {
  const token = extractPhaseToken(dirName);
  if (token.toUpperCase() === normalized.toUpperCase()) return true;
  const stripped = stripProjectCodePrefix(dirName);
  if (stripped !== dirName) {
    const strippedToken = extractPhaseToken(stripped);
    if (strippedToken.toUpperCase() === normalized.toUpperCase()) return true;
  }
  return false;
}

export = {
  escapeRegex,
  OPTIONAL_PROJECT_CODE_PREFIX_SOURCE,
  OPTIONAL_PHASE_TAG_SOURCE,
  stripProjectCodePrefix,
  normalizePhaseName,
  getMilestoneFromPhaseId,
  getPhaseDirFromPhaseId,
  phaseMarkdownRegexSource,
  phaseMarkdownRegexSourceExact,
  comparePhaseNum,
  extractPhaseToken,
  phaseTokenMatches,
};