// lib/review/critic-diff.mjs
// Rule A and the rule-B record for the plan gate (decision 43).
//
// Why: from round 2 on, the critic loop counts a new MAJOR that cites plan text
// outside the diff since the last reviewed round as minor (rule A), so a loop of
// critic rounds converges on what changed instead of re-litigating text that was
// already reviewed. That needs a line diff between two operative plan texts
// that is deterministic: the same two texts always give the same hunks, so the
// same findings always give the same verdict.
//
// lineDiff(oldText, newText) -> { inside, oldToNew, hunks }
//   Lines are 1-based operative lines; CRLF is normalized first.
//   inside   Set of every inserted or changed new line; for a pure-deletion
//            hunk also the new lines on both sides of the deletion point.
//   oldToNew oldToNew[o] = the new line an unchanged old line moved to, else
//            null (index 0 is null).
//   hunks    [{oldStart, oldEnd, newStart, newEnd}], inclusive ranges in order;
//            an empty side has end = start - 1.
//   How: trim the common prefix and suffix; anchor on lines that occur exactly
//   once in both texts, keep the longest increasing subsequence of anchors and
//   recurse between them; a gap with no unique line uses an LCS table, ties
//   resolved toward matching the earliest old line.
//
// countRound({round, previous, base, baseNote, current, planPaths, findings, marks})
//   -> { findings, resolved, diffBase, diffNote, lowered }
//   Decides each finding's counted severity for one critic round (RULE_A,
//   RULE_B below). `current` = {text, sha256, fullToOp, opToFull}, built by the
//   caller from the plan gate's operativeLines and planHash; `base` = {sha256,
//   text} is the operative text the previous round reviewed, or null.
//   Rule A is on only from round 2, with a base whose sha256 is the previous
//   verdict's plan_sha256 and differs from the plan now. Otherwise the round is
//   counted as before (each finding at its reported severity, plus the rule-B
//   record) and `diffNote` says why in one line. With rule A on, a current
//   finding outside the diff is matched to a previous one only when their
//   texts overlap (`contentOverlap` ≥ `DEFAULT_THRESHOLD`) and the current one
//   sits at the previous one's mapped line, or (for a previous finding with no
//   plan line) has its id, or both texts hold `ANCHOR_MIN_CONTENT_WORDS`
//   content words in the same file class; a new finding never carries a
//   previous finding's id: a repeated id gets `<rule_key>#n`, as in dedup.
//   A previous finding stays counted until every reviewer that raised it marks
//   it resolved, no reviewer says it is not, and nobody re-reports it.
//   Carried findings come first (previous order), then new ones (dedup order).
//
// Trust limit: anything that can write the plan can rewrite the previous
// verdict's plan_sha256 and plant a matching base snapshot. That was already
// the stated limit of the verdict block; rule A raises what such a forgery
// buys. An unchanged base lowers nothing.
//
// Pure: no I/O, and it never reads the plan gate (one dependency direction).
//
// Credit: patience-style anchoring (unique-line anchors kept by their longest
// increasing subsequence), the idea behind Bram Cohen's patience diff; the code
// here is written fresh.

import { resolve } from 'node:path';
import {
  normalizeSeverity, contentOverlap, contentTokens, DEFAULT_THRESHOLD, ANCHOR_MIN_CONTENT_WORDS, SEVERITIES,
  isSecurityKey, keysOf, isSecurity, ruleB,
} from './plan-review-dedup.mjs';
import { computeFindingId } from '../parsers/finding-id.mjs';

export { isSecurityKey };

export const RULE_A = 'Rule A: from round 2 on, a new major finding that cites a plan line outside the diff since the last reviewed text counts as minor; a blocker, a security finding and a finding with no plan line count at full severity, and a previous finding stays counted until it is marked resolved.';
export const RULE_B = 'Rule B: a major that a named test, `Regression:` command or gate in the plan will fail on during execution is minor — never a blocker, never a security finding.';

// The optional voyage.plan-verdict/1 fields of decision 43; absent means round-1 behaviour.
export const DIFF_FIELDS = Object.freeze([
  // top level
  'diff_base', 'diff_note', 'resolved',
  // per finding
  'op_line', 'op_line_end', 'line_end', 'rule_keys', 'original_severity', 'lowered_by', 'caught_by',
  'lowering_refused', 'carried_from',
]);

const toLines = (text) => {
  const t = String(text ?? '').replace(/\r\n?/g, '\n');
  if (t === '') return [];
  const out = t.split('\n');
  if (out[out.length - 1] === '') out.pop();
  return out;
};

/** Indexes (into `items`) of a longest strictly increasing subsequence of items[k].b; earliest on ties. */
function lisByB(items) {
  const tails = []; // tails[len-1] = index into items of the smallest tail
  const prev = new Array(items.length).fill(-1);
  for (let k = 0; k < items.length; k++) {
    const v = items[k].b;
    let lo = 0;
    let hi = tails.length;
    while (lo < hi) {
      const mid = (lo + hi) >> 1;
      if (items[tails[mid]].b < v) lo = mid + 1; else hi = mid;
    }
    if (lo > 0) prev[k] = tails[lo - 1];
    tails[lo] = k;
  }
  const out = [];
  for (let k = tails.length ? tails[tails.length - 1] : -1; k !== -1; k = prev[k]) out.push(k);
  return out.reverse();
}

/** LCS over a[aLo..aHi) x b[bLo..bHi); pushes matched [i, j] pairs in order. */
function lcsGap(a, aLo, aHi, b, bLo, bHi, pairs) {
  const n = aHi - aLo;
  const m = bHi - bLo;
  const w = m + 1;
  // L[i*w + j] = LCS length of a[aLo+i..aHi) and b[bLo+j..bHi)
  const L = new Uint32Array((n + 1) * w);
  for (let i = n - 1; i >= 0; i--) {
    for (let j = m - 1; j >= 0; j--) {
      L[i * w + j] = a[aLo + i] === b[bLo + j]
        ? L[(i + 1) * w + j + 1] + 1
        : Math.max(L[(i + 1) * w + j], L[i * w + j + 1]);
    }
  }
  let i = 0;
  let j = 0;
  while (i < n && j < m) {
    if (a[aLo + i] === b[bLo + j]) {
      pairs.push([aLo + i, bLo + j]);
      i += 1;
      j += 1;
    } else if (L[i * w + j + 1] >= L[(i + 1) * w + j]) {
      j += 1; // keep old line i for the earliest match
    } else {
      i += 1;
    }
  }
}

/** Match a[aLo..aHi) against b[bLo..bHi); pushes matched [i, j] pairs (0-based) in order. */
function matchRange(a, aLo, aHi, b, bLo, bHi, pairs) {
  while (aLo < aHi && bLo < bHi && a[aLo] === b[bLo]) {
    pairs.push([aLo, bLo]);
    aLo += 1;
    bLo += 1;
  }
  const tail = [];
  while (aLo < aHi && bLo < bHi && a[aHi - 1] === b[bHi - 1]) {
    aHi -= 1;
    bHi -= 1;
    tail.push([aHi, bHi]);
  }
  if (aLo < aHi && bLo < bHi) {
    const count = new Map(); // line -> {na, nb, a, b}
    for (let i = aLo; i < aHi; i++) {
      const c = count.get(a[i]) ?? { na: 0, nb: 0, a: -1, b: -1 };
      c.na += 1;
      c.a = i;
      count.set(a[i], c);
    }
    for (let j = bLo; j < bHi; j++) {
      const c = count.get(b[j]);
      if (!c) continue;
      c.nb += 1;
      c.b = j;
    }
    const anchors = [];
    for (let i = aLo; i < aHi; i++) {
      const c = count.get(a[i]);
      if (c.na === 1 && c.nb === 1) anchors.push({ a: c.a, b: c.b });
    }
    if (anchors.length > 0) {
      let pa = aLo;
      let pb = bLo;
      for (const k of lisByB(anchors)) {
        const { a: ia, b: ib } = anchors[k];
        matchRange(a, pa, ia, b, pb, ib, pairs);
        pairs.push([ia, ib]);
        pa = ia + 1;
        pb = ib + 1;
      }
      matchRange(a, pa, aHi, b, pb, bHi, pairs);
    } else {
      lcsGap(a, aLo, aHi, b, bLo, bHi, pairs);
    }
  }
  for (let k = tail.length - 1; k >= 0; k--) pairs.push(tail[k]);
}

/**
 * Deterministic line diff of two operative texts.
 * @param {string} oldText
 * @param {string} newText
 * @returns {{inside: Set<number>, oldToNew: Array<number|null>, hunks: Array<{oldStart: number, oldEnd: number, newStart: number, newEnd: number}>}}
 */
export function lineDiff(oldText, newText) {
  const a = toLines(oldText);
  const b = toLines(newText);
  const pairs = [];
  matchRange(a, 0, a.length, b, 0, b.length, pairs);
  const oldToNew = new Array(a.length + 1).fill(null);
  for (const [i, j] of pairs) oldToNew[i + 1] = j + 1;
  const hunks = [];
  const inside = new Set();
  let pi = -1;
  let pj = -1;
  for (const [qi, qj] of [...pairs, [a.length, b.length]]) {
    if (qi > pi + 1 || qj > pj + 1) {
      const h = { oldStart: pi + 2, oldEnd: qi, newStart: pj + 2, newEnd: qj };
      hunks.push(h);
      if (h.newEnd >= h.newStart) {
        for (let n = h.newStart; n <= h.newEnd; n++) inside.add(n);
      } else {
        if (h.newStart - 1 >= 1) inside.add(h.newStart - 1);
        if (h.newStart <= b.length) inside.add(h.newStart);
      }
    }
    pi = qi;
    pj = qj;
  }
  return { inside, oldToNew, hunks };
}

// ---- counting (rule A, rule B) ----------------------------------------------------

// Lower index = more severe; an unrated severity counts as blocker.
const rankOf = s => SEVERITIES.indexOf(s);
const countedOf = s => normalizeSeverity(s) ?? 'blocker';
const higher = (a, b) => (rankOf(a) <= rankOf(b) ? a : b);
const hasOwn = (o, k) => Object.prototype.hasOwnProperty.call(o, k);

function union(...lists) {
  const out = [];
  for (const list of lists) {
    for (const x of Array.isArray(list) ? list : []) if (!out.includes(x)) out.push(x);
  }
  return out;
}

/** A current finding in today's verdict shape, plus the pass-through fields. */
function project(f) {
  const rated = normalizeSeverity(f.severity);
  const out = {
    id: f.id ?? null,
    severity: rated ?? 'blocker',
    rule_key: f.rule_key ?? null,
    file: f.file ?? null,
    line: f.line ?? null,
    text: typeof f.text === 'string' ? f.text : '',
    raised_by: Array.isArray(f.raised_by) ? [...f.raised_by] : [],
  };
  if (rated === null) out.severity_defaulted = true;
  if (Number.isInteger(f.line_end)) out.line_end = f.line_end;
  if (Array.isArray(f.rule_keys)) out.rule_keys = [...f.rule_keys];
  return out;
}

/**
 * Where a current finding sits in the operative text, or null when it has no
 * plan line (another file, no line, a line in the review log, past the end,
 * or a `line_end` that does not map).
 */
function placeOf(f, fullToOp, planSet) {
  if (typeof f.file !== 'string' || f.file === '' || !planSet.has(resolve(f.file))) return null;
  const at = l => (Number.isInteger(l) && l >= 1 && l < fullToOp.length ? fullToOp[l] ?? null : null);
  const start = at(f.line);
  if (start === null) return null;
  const hasEnd = f.line_end !== undefined && f.line_end !== null;
  let end = start;
  if (hasEnd) {
    const e = Number.isInteger(f.line_end) && f.line_end >= f.line ? at(f.line_end) : null;
    if (e === null) return null;
    end = Math.max(start, e);
  }
  return { start, end, hasEnd };
}

const contentSize = t => new Set(contentTokens(typeof t === 'string' ? t : '')).size;

/** Does current finding `f` (placed at `pl`) sit at previous finding `p`'s mapped line? */
function atSpot(pl, p, d) {
  if (pl === null) return false;
  if (!hasOwn(p, 'op_line') || !Number.isInteger(p.op_line)) return false;
  const n = d.oldToNew[p.op_line] ?? null;
  return n !== null && n >= pl.start && n <= pl.end;
}

/** Does current finding `f` (placed at `pl`, outside the diff) re-report previous finding `p`? */
function sameFinding(f, pl, p, d) {
  if (contentOverlap(f.text, p.text) < DEFAULT_THRESHOLD) return false;
  if (atSpot(pl, p, d)) return true;
  const pCites = hasOwn(p, 'op_line');
  // The id is compared only for a previous finding with no plan line.
  if (!pCites && typeof f.id === 'string' && f.id === p.id) return true;
  const sameClass = (pl !== null && pCites) ||
    (typeof f.file === 'string' && f.file !== '' && f.file === p.file);
  if (!sameClass) return false;
  return contentSize(f.text) >= ANCHOR_MIN_CONTENT_WORDS && contentSize(p.text) >= ANCHOR_MIN_CONTENT_WORDS;
}

/** A previous finding leaves the count only on its raisers' true, nobody's false. */
function isResolved(p, marks) {
  const ms = marks.filter(m => m && typeof m.id === 'string' && m.id === p.id);
  if (!ms.some(m => m.resolved === true)) return false;
  if (ms.some(m => m.resolved === false)) return false;
  const raisers = Array.isArray(p.raised_by) ? p.raised_by : [];
  return raisers.every(r => ms.some(m => m.agent === r && m.resolved === true));
}

/** A previous finding carried into this round, with its matches' severities and keys. */
function carry(p, matched, d, current, prevRound) {
  const pSev = countedOf(p.severity);
  const orig = normalizeSeverity(p.original_severity);
  const wasLowered = orig !== null && rankOf(orig) < rankOf(pSev);
  const keys = union(keysOf(p), ...matched.map(m => keysOf(m.f)));
  let sev;
  if (wasLowered) {
    if (keys.some(isSecurityKey)) sev = matched.reduce((s, m) => higher(s, m.sev), orig);
    else if (matched.some(m => m.sev === 'blocker')) sev = 'blocker';
    else sev = pSev;
  } else {
    sev = matched.reduce((s, m) => higher(s, m.sev), pSev);
  }
  const out = {
    id: p.id ?? null,
    severity: sev,
    rule_key: p.rule_key ?? null,
    file: p.file ?? null,
    line: p.line ?? null,
    text: typeof p.text === 'string' ? p.text : '',
    raised_by: union(p.raised_by, ...matched.map(m => m.f.raised_by)),
  };
  if (p.severity_defaulted === true) out.severity_defaulted = true;
  if (Number.isInteger(p.line_end)) out.line_end = p.line_end;
  if (keys.length > 0) out.rule_keys = keys;
  if (hasOwn(p, 'op_line')) {
    // A plan line: follow the diff. Its own line edited (or no op_line already):
    // keep the old line, op_line null, never re-mapped from a stale position.
    const n = Number.isInteger(p.op_line) ? (d.oldToNew[p.op_line] ?? null) : null;
    out.op_line = n;
    if (n !== null) {
      out.line = current.opToFull[n] ?? out.line;
      const e = Number.isInteger(p.op_line_end) ? (d.oldToNew[p.op_line_end] ?? null) : null;
      const eFull = e !== null ? (current.opToFull[e] ?? null) : null;
      if (eFull !== null) {
        out.line_end = eFull;
        out.op_line_end = e;
      } else {
        delete out.line_end;
      }
    } else if (hasOwn(p, 'op_line_end')) {
      out.op_line_end = null;
    }
  }
  out.carried_from = Number.isInteger(p.carried_from) ? p.carried_from : prevRound;
  if (wasLowered) {
    if (rankOf(sev) > rankOf(orig)) {
      out.original_severity = orig;
      if (typeof p.lowered_by === 'string') out.lowered_by = p.lowered_by;
      if (typeof p.caught_by === 'string') out.caught_by = p.caught_by;
    }
  } else {
    if (orig !== null && orig !== sev) out.original_severity = orig;
    if (typeof p.lowering_refused === 'string') out.lowering_refused = p.lowering_refused;
    if (typeof p.caught_by === 'string') out.caught_by = p.caught_by;
  }
  return out;
}

/** One line: the reason a round is counted fully. */
export const oneLine = s => String(s).replace(/\s*[\r\n]+\s*/g, ' ').trim();

/**
 * Count one critic round by rule A (from round 2, against the diff since the
 * text the previous round reviewed) and record rule B (every round).
 * Pure and deterministic.
 * @param {{round: number, previous: object|null, base: {sha256: string, text: string}|null,
 *   baseNote?: string|null, current: {text: string, sha256: string, fullToOp: Array<number|null>, opToFull: Array<number|null>},
 *   planPaths: string[], findings: object[], marks: Array<{agent: string, id: string, resolved: boolean}>}} input
 * @returns {{findings: object[], resolved: string[]|null, diffBase: string|null, diffNote: string|null, lowered: number}}
 */
export function countRound({ round, previous, base, baseNote, current, planPaths, findings, marks }) {
  const prevRound = previous && Number.isInteger(previous.round) ? previous.round : null;
  let diffNote = null;
  let d = null;
  if (Number.isInteger(round) && round >= 2 && prevRound !== null) {
    if (!base || typeof base !== 'object') {
      diffNote = typeof baseNote === 'string' && baseNote.trim() !== ''
        ? oneLine(baseNote)
        : `no base snapshot of round ${prevRound}'s reviewed text; full counting`;
    } else if (typeof base.sha256 !== 'string' || base.sha256 !== previous.plan_sha256) {
      diffNote = `the base snapshot is not the text round ${prevRound} reviewed; full counting`;
    } else if (base.sha256 === current.sha256) {
      diffNote = `the plan has not changed since round ${prevRound}; full counting`;
    } else if (typeof base.text !== 'string') {
      diffNote = `the base snapshot of round ${prevRound} has no text; full counting`;
    } else {
      d = lineDiff(base.text, current.text);
    }
  }
  const ruleA = d !== null;
  const planSet = new Set(Array.isArray(planPaths) ? planPaths : []);
  const fullToOp = Array.isArray(current?.fullToOp) ? current.fullToOp : [];
  const prevFindings = ruleA && Array.isArray(previous.findings)
    ? previous.findings.filter(p => p && typeof p === 'object')
    : [];
  const markList = Array.isArray(marks) ? marks : [];

  const matchedTo = new Map(prevFindings.map(p => [p, []]));
  // A new finding never carries a previous finding's id (dedup's `<rule_key>#n` scheme).
  const takenIds = new Set(prevFindings.map(p => p.id).filter(id => typeof id === 'string'));
  const fresh = [];
  for (const f of Array.isArray(findings) ? findings : []) {
    const o = project(f);
    const b = ruleB(f, o.severity);
    o.severity = b.severity;
    Object.assign(o, b.record);
    const pl = placeOf(f, fullToOp, planSet);
    let inside = false;
    if (ruleA && pl) {
      for (let n = pl.start; n <= pl.end && !inside; n++) inside = d.inside.has(n);
    }
    if (ruleA && !inside) {
      const p = prevFindings.find(q => sameFinding(f, pl, q, d));
      if (p) {
        matchedTo.get(p).push({ f, sev: o.severity });
        continue;
      }
    }
    if (pl) {
      o.op_line = pl.start;
      if (pl.hasEnd) o.op_line_end = pl.end;
    }
    if (ruleA && o.severity === 'major' && pl && !inside && !isSecurity(f)) {
      o.severity = 'minor';
      o.original_severity = 'major';
      o.lowered_by = `rule A: outside the diff since round ${prevRound}`;
    }
    if (typeof o.id === 'string' && takenIds.has(o.id)) {
      let n = 2;
      let id;
      while (takenIds.has(id = computeFindingId(String(o.file || 'unknown'), Number.isInteger(o.line) ? o.line : 0, `${o.rule_key ?? 'unknown'}#${n}`))) n += 1;
      o.id = id;
    }
    if (typeof o.id === 'string') takenIds.add(o.id);
    fresh.push(o);
  }

  const carried = [];
  const resolved = [];
  for (const p of prevFindings) {
    const matched = matchedTo.get(p);
    if (matched.length === 0 && isResolved(p, markList)) {
      resolved.push(p.id);
      continue;
    }
    carried.push(carry(p, matched, d, current, prevRound));
  }

  const out = [...carried, ...fresh];
  const lowered = out.filter((x) => {
    const o = normalizeSeverity(x.original_severity);
    return o !== null && rankOf(o) < rankOf(x.severity);
  }).length;
  return {
    findings: out,
    resolved: ruleA ? resolved : null,
    diffBase: ruleA ? base.sha256 : null,
    diffNote,
    lowered,
  };
}