// user-data.mjs — Spor C fase C2.1: user-owned storage + ambient org context.
//
// This module is a PURE RESOLVER. It NEVER writes and never spawns anything —
// it only resolves user-owned paths and builds a compact, deterministic
// summary from file contents it is HANDED (no fs read of its own). All org-/
// config writing happens elsewhere, gated, via lib/atomic-write + lib/backup.
//
// Why a user-owned dir? Org context + the C1 scheduler config previously lived
// inside the plugin directory (gitignored), so a plugin reinstall / marketplace
// move blew them away. Resolving them under ~/.claude/ms-ai-architect/ — a
// sibling of ~/.claude/plugins/, independent of pluginRoot — makes them survive
// reinstall (acceptance K2). Privacy is preserved: this path is in no git repo.
//
// Zero dependencies beyond node:os/path. Every function is pure.

import { homedir } from 'node:os';
import { join } from 'node:path';

// The plugin's folder under ~/.claude/ (sibling of ~/.claude/plugins/).
export const USER_DATA_DIRNAME = 'ms-ai-architect';

// The scheduler config filename. Single source of truth shared with
// detection-schedule.mjs (C1) so loadScheduleConfig stays backward-compatible.
export const CONFIG_FILENAME = 'ms-ai-architect.local.md';

// The five structured onboarding files, in the order they are surfaced.
export const ORG_FILES = Object.freeze([
  'organization-profile.md',
  'technology-stack.md',
  'security-compliance.md',
  'architecture-decisions.md',
  'business-references.md',
]);

// The optional free-prose file (C2.2, #3): "everything else you want the plugin
// to know". Deliberately NOT in ORG_FILES — its presence is optional and must
// NOT affect the onboarding-completeness count (the SessionStart hook gates that
// on `count < ORG_FILES.length`). It is read for the ambient summary only.
export const FREE_CONTEXT_FILE = 'free-context.md';

const FREE_CONTEXT_LABEL = 'Fri kontekst';

// Minimum line budget: what a small, designed onboarding is allowed to spend
// even when it has fewer files than lines. Above this floor the line budget is
// derived from the file count (see coverageLineBudget) — because at scale the
// binding cost is chars, not lines, and a fixed line count silently decides
// WHICH documents exist.
const DEFAULT_SUMMARY_CAP = 25;

// The shortest value a coverage line may carry before it stops being a summary
// and becomes a fragment. It bounds how far the one-line-per-file guarantee can
// stretch: at most floor(maxTotalLen / this) lines.
//
// Anchored to the designed onboarding's own field lengths, measured 2026-08-26
// over the real artefact (~/.claude/ms-ai-architect/org, 18 structured fields):
// median 34 chars, mean 75, max 278. 60 keeps the median field whole with
// headroom and cuts the mean one by about a fifth; below it the median field
// starts breaking mid-sentence. With the 4000-char budget this permits 66 lines.
const MIN_COVERAGE_VALUE_LEN = 60;

// Total char budget for the field VALUES of one summary, shared across the
// fields that survive the line budget (see coverageLineBudget).
//
// Why a TOTAL budget and not the per-field cap it replaces: the summary is
// injected ambiently at EVERY session start, so what costs is the total, not
// any single field — and a per-field cap cannot see how much of that total is
// unspent. Measured 2026-08-26 by running this function with the hook's
// defaults over the designed onboarding (19 fields, ~52 chars each): it spent
// ~1000 of the 4000 chars the mechanism already permitted, while still cutting
// any field past 160 chars — a 300-char answer lost 47 %, a 2000-char one 92 %.
// free-context.md, the one slot where the user writes freely, was cut the same
// way through its own code path (collapseProse before capValue).
//
// Why 4000 specifically: that is exactly what the old form already permitted at
// its worst case — DEFAULT_SUMMARY_CAP (25) lines x the old 160-char per-field
// cap. The budget is therefore cost-neutral against today's ceiling and
// strictly better below it. Raising this number raises the cost of every
// session in the repo.
//
// The per-field floor this comment used to promise (4000/25 = 160, "reached
// only at exactly 25 fields") held only while the line cap was fixed at 25. It
// is not a property of the budget — it was a property of the defect the line
// cap turned out to be. The floor that survives is MIN_COVERAGE_VALUE_LEN,
// which is what the line budget is derived FROM rather than what falls out of
// it.
const DEFAULT_MAX_TOTAL_LEN = 4000;

/** The user-owned data root: ~/.claude/ms-ai-architect/ (survives reinstall). */
export function resolveUserDataDir(home = homedir()) {
  return join(home, '.claude', USER_DATA_DIRNAME);
}

/** The user-owned org/ directory (the five structured onboarding files). */
export function resolveOrgDir(home = homedir()) {
  return join(resolveUserDataDir(home), 'org');
}

/** The user-owned scheduler config path (same filename as the C1 plugin-root one). */
export function resolveConfigPath(home = homedir()) {
  return join(resolveUserDataDir(home), CONFIG_FILENAME);
}

/** Drop a leading `---`…`---` YAML frontmatter block, if present. */
function stripFrontmatter(text) {
  if (!text.startsWith('---')) return text;
  const m = text.match(/^---\n[\s\S]*?\n---\n?/);
  return m ? text.slice(m[0].length) : text;
}

/**
 * Extract `## Header` → collapsed-body pairs from one org file's markdown.
 * Frontmatter and the leading H1 are ignored; H2 sections with an empty body
 * are skipped. Body lines are collapsed to a single spaced line. Pure.
 * @param {string} content
 * @returns {Array<[string, string]>}
 */
function extractSections(content) {
  const lines = stripFrontmatter(content).split('\n');
  const out = [];
  let header = null;
  let body = [];
  const flush = () => {
    if (header !== null) {
      const value = body.join(' ').replace(/\s+/g, ' ').trim();
      if (value) out.push([header, value]);
    }
  };
  for (const line of lines) {
    const h2 = line.match(/^##\s+(.+?)\s*$/);
    if (h2) {
      flush();
      header = h2[1];
      body = [];
    } else if (header !== null && !/^#\s/.test(line)) {
      body.push(line);
    }
  }
  flush();
  return out;
}

/**
 * Collapse a markdown document to one prose line: drop frontmatter and every
 * header line, then squeeze whitespace. Used for the free-context file, which is
 * ONE free field (not structured H2 sections) and may be plain prose — so it is
 * surfaced whole rather than per-section, never silently dropped. Pure.
 * @param {string} content
 * @returns {string}
 */
function collapseProse(content) {
  return stripFrontmatter(content)
    .split('\n')
    .filter((line) => !/^#{1,6}\s/.test(line))
    .join(' ')
    .replace(/\s+/g, ' ')
    .trim();
}

/** Truncate a field value to maxValueLen, appending an ellipsis when cut. Pure. */
function capValue(value, maxValueLen) {
  return value.length > maxValueLen
    ? `${value.slice(0, Math.max(0, maxValueLen - 1)).trimEnd()}…`
    : value;
}

/**
 * Max-min fair allocation of a total char budget over field values: a field
 * shorter than its even share is kept whole and leaves its slack to the longer
 * ones, iterating until nothing more can be settled. This is what a per-field
 * cap cannot express — one long, important answer surviving because five short
 * ones did not need their share. Deterministic and pure; returns one allowance
 * per input length, in input order.
 * @param {number[]} lengths
 * @param {number} budget
 * @returns {number[]}
 */
function allocateBudget(lengths, budget) {
  const allowance = new Array(lengths.length).fill(0);
  let open = lengths.map((_, i) => i);
  let remaining = budget;
  while (open.length > 0) {
    const share = Math.floor(remaining / open.length);
    const settled = open.filter((i) => lengths[i] <= share);
    if (settled.length === 0) {
      // Every field still open wants more than the even share: split the rest,
      // handing the indivisible remainder to the earliest fields.
      let rest = remaining - share * open.length;
      for (const i of open) {
        allowance[i] = share + (rest > 0 ? 1 : 0);
        if (rest > 0) rest -= 1;
      }
      break;
    }
    for (const i of settled) {
      allowance[i] = lengths[i];
      remaining -= lengths[i];
    }
    open = open.filter((i) => lengths[i] > share);
  }
  return allowance;
}

/**
 * The org files to surface, in deterministic order: the canonical ORG_FILES
 * first, then any OTHER `.md` file the user has added to org/, sorted by name.
 * The free-prose file is excluded — callers append it last under its own label.
 *
 * Why it exists: the summary and the hook that feeds it used to iterate the
 * frozen ORG_FILES list, so a seventh file in org/ never reached the model at
 * all (measured 2026-08-26). Both sides now order their files through here.
 *
 * Pure: takes names (a readdir listing, or a content map's keys) and reads
 * nothing.
 * @param {string[]} names
 * @returns {string[]}
 */
export function orderOrgFiles(names) {
  if (!Array.isArray(names)) return [];
  const present = new Set(names.filter((n) => typeof n === 'string' && n.endsWith('.md')));
  const extra = [...present]
    .filter((n) => !ORG_FILES.includes(n) && n !== FREE_CONTEXT_FILE)
    .sort();
  return [...ORG_FILES.filter((n) => present.has(n)), ...extra];
}

/**
 * The line budget for one summary: enough lines to give every file at least one
 * field, but never so many that a line drops below MIN_COVERAGE_VALUE_LEN, and
 * never fewer than DEFAULT_SUMMARY_CAP.
 *
 * Why the count is derived and not a constant: this summary is injected
 * ambiently at session start, BEFORE any question exists, so there is no
 * relevance signal to rank fields against. A fixed line count therefore does
 * not reduce — it SELECTS, by whatever order the files happen to be in.
 * Measured 2026-08-26 (bake-off arm A2b, flat org/, 55 corpus documents): 61
 * files and 183 fields in, 24 fields out, all from 8 files, with 1013 of the
 * 4000 value chars unspent. When you cannot rank, the honest substitute is to
 * cover: spend the budget across documents rather than on the first few.
 *
 * Pure.
 * @param {number} fileCount
 * @param {number} maxTotalLen
 * @returns {number}
 */
function coverageLineBudget(fileCount, maxTotalLen) {
  const affordable = Math.floor(maxTotalLen / MIN_COVERAGE_VALUE_LEN);
  return Math.max(DEFAULT_SUMMARY_CAP, Math.min(fileCount + 1, affordable));
}

/**
 * Choose which of the collected fields survive, breadth-first across their
 * source files: every file gives up its first field before any file gives up
 * its second. Returns a Set of indices into `fields` — SELECTION only; the
 * caller still emits in the original file order, so reading order is unchanged.
 *
 * Pure.
 * @param {Array<[string, string, string]>} fields  [header, value, sourceFile]
 * @param {number} room  how many fields may be emitted
 * @returns {Set<number>}
 */
function pickBreadthFirst(fields, room) {
  const byFile = new Map();
  fields.forEach(([, , file], i) => {
    if (!byFile.has(file)) byFile.set(file, []);
    byFile.get(file).push(i);
  });
  const picked = new Set();
  const queues = [...byFile.values()];
  for (let round = 0; picked.size < room; round++) {
    let handedOut = false;
    for (const q of queues) {
      if (round >= q.length) continue;
      picked.add(q[round]);
      handedOut = true;
      if (picked.size >= room) break;
    }
    if (!handedOut) break; // every file exhausted
  }
  return picked;
}

/**
 * Build a compact, deterministic org-context summary from org file contents.
 * PURE — takes a `{ filename: contentString }` map (the caller reads the files)
 * and returns a budget-bounded `Header: value` block, one field per line, in
 * orderOrgFiles order then header order. Empty/garbage input => "".
 *
 * Robust by design: it extracts whatever H2 sections the onboarding agent
 * wrote rather than hard-coding field names, so header wording can drift
 * without silently emptying the summary.
 *
 * @param {Record<string, string|null>|null|undefined} orgFiles
 * @param {{cap?: number, maxTotalLen?: number}} [opts] `cap` is a hard line
 *   ceiling; omit it to get the coverage-derived budget, which is the form the
 *   hook uses.
 * @returns {string}
 */
export function buildOrgSummary(orgFiles, opts = {}) {
  if (!orgFiles || typeof orgFiles !== 'object') return '';
  const maxTotalLen = opts.maxTotalLen ?? DEFAULT_MAX_TOTAL_LEN;
  // An explicit cap is a plain ceiling (callers that ask for N lines get N).
  // The DEFAULT is derived from how many files there are, so growth in org/
  // widens the summary instead of silently hiding documents behind it.
  const cap =
    opts.cap ??
    coverageLineBudget(
      orderOrgFiles(Object.keys(orgFiles)).length + (orgFiles[FREE_CONTEXT_FILE] ? 1 : 0),
      maxTotalLen,
    );

  // Collect UNCUT [header, value, sourceFile] triples first: the char budget can
  // only be spent fairly once it is known which fields the line budget emits.
  // Provenance is carried because the reduction unit is the DOCUMENT, not the
  // field — without it the cut cannot tell whether it is dropping a file's
  // fifth field or its only one.
  const fields = [];
  for (const name of orderOrgFiles(Object.keys(orgFiles))) {
    const content = orgFiles[name];
    if (typeof content !== 'string' || !content.trim()) continue;
    for (const [header, value] of extractSections(content)) fields.push([header, value, name]);
  }

  // Free-prose context (C2.2, #3): the optional free-text file, surfaced LAST as
  // one "Fri kontekst" field regardless of internal markdown structure, so a
  // plain paragraph is never silently dropped (acceptance K3).
  const freeContent = orgFiles[FREE_CONTEXT_FILE];
  let hasFreeContext = false;
  if (typeof freeContent === 'string' && freeContent.trim()) {
    const body = collapseProse(freeContent);
    if (body) {
      fields.push([FREE_CONTEXT_LABEL, body, FREE_CONTEXT_FILE]);
      hasFreeContext = true;
    }
  }

  if (fields.length === 0) return '';

  // Budget 1 — lines: over cap, keep (cap-1) fields plus a marker for the rest.
  // WHICH fields is decided breadth-first across source files, so the cut is a
  // reduction and not a fixed-order selection (see coverageLineBudget). The
  // emission order below is still the file order, so reading order is stable.
  //
  // "Fri kontekst" is exempt from that cut. It is appended LAST so it reads last,
  // which under a plain head-slice made it the FIRST field to disappear — and it
  // is the one slot the user writes freely in, which onboarding-agent.md calls
  // the single category that most sharpens the advice. Position in the summary
  // is a reading order, not a priority order; the cut must not conflate them.
  const overflow = fields.length > cap;
  let kept = fields;
  if (overflow) {
    const room = Math.max(0, cap - 1); // fields emittable alongside the marker
    const structured = hasFreeContext ? fields.slice(0, -1) : fields;
    const picked = pickBreadthFirst(structured, hasFreeContext ? Math.max(0, room - 1) : room);
    kept = structured.filter((_, i) => picked.has(i));
    if (hasFreeContext && room >= 1) kept.push(fields[fields.length - 1]);
  }

  // Budget 2 — chars: shared max-min fairly over the fields actually emitted.
  const allowance = allocateBudget(kept.map(([, value]) => value.length), maxTotalLen);
  const lines = kept.map(([header, value], i) => `${header}: ${capValue(value, allowance[i])}`);
  if (overflow) {
    // Report the files left out, not only the fields. A file with nothing
    // emitted is invisible to the session, and the measured failure mode was
    // exactly that it was invisible SILENTLY — the user believes the plugin is
    // onboarded while the advice is generic.
    const keptFiles = new Set(kept.map(([, , file]) => file));
    const allFilesCount = new Set(fields.map(([, , file]) => file)).size;
    const droppedFiles = allFilesCount - keptFiles.size;
    lines.push(
      `… (+${fields.length - kept.length} flere felt; ` +
        `${droppedFiles} av ${allFilesCount} filer helt utelatt)`,
    );
  }
  return lines.join('\n');
}