/**
 * Approval gates A/B/C of the upstream loop: the pure decision core plus the
 * approval.md / plan io it needs.
 *
 * No DSH runtime is imported here. Every decision function takes plain values;
 * where it must touch the filesystem it does so only through an explicit
 * repository root and only synchronously (`readFileSync` / `existsSync`).
 *
 * Failure policy mirrors the bash hooks: a call that references no plan is
 * never blocked, while a *referenced* plan that cannot be read or tied to an
 * approved change is denied (fail closed). Parsing never throws: malformed
 * YAML or markdown degrades to "missing", which the gates reject.
 */

import { createHash } from 'node:crypto'
import { readFileSync, statSync } from 'node:fs'
import { basename, isAbsolute, join, relative, resolve, sep } from 'node:path'

export const APPROVAL_FILE = 'approval.md'
export const PLANS_DIR = join('docs', 'superpowers', 'plans')
export const CHANGE_DIR = join('openspec', 'changes')
export const SDD_DIR = join('.superpowers', 'sdd')

const SPEC_DENY = 'plan must carry **Spec:** pointing to openspec/changes/<id>'
const APPROVAL_DENY = 'approval.md is written only by /approve'
const PLAN_NO_APPROVAL = 'no plan approval'
const PLAN_CHANGED = 'plan changed after approval'
const PLAN_CHANGED_DENY = 'plan changed after approval; re-approve'

/** Scalar keys of each approval.md section, in serialization order. */
const SECTION_FIELDS = {
  design: ['by', 'at'],
  plan: ['by', 'at', 'sha256'],
}

/** `openspec/changes/<id>` anywhere in a path (also inside an absolute path). */
const CHANGE_PATH = /(?:^|\/)openspec\/changes\/([^/\s]+)/u
/** `.superpowers/sdd/<plan-name>` anywhere in a path or a prompt. */
const SDD_PATH = /(?:^|\/)\.superpowers\/sdd\/([^/\s]+)/u
/** A direct plan reference; the match ends at `.md`, prose may follow it. */
const DIRECT_PLAN = /^docs\/superpowers\/plans\/([^/\s"'`()<>[\]{}]+\.md)/u

const DIRECT_PREFIX = 'docs/superpowers/plans/'
const SDD_PREFIX = '.superpowers/sdd/'

/**
 * Characters that end a path token when scanning a prompt backwards. `=`
 * separates `--flag=<path>` and `:` ends a prose label like `Plan:<path>`.
 */
const TOKEN_STOP = new Set([
  ' ',
  '\t',
  '\n',
  '\r',
  '"',
  "'",
  '`',
  '(',
  ')',
  '[',
  ']',
  '{',
  '}',
  '<',
  '>',
  ',',
  ';',
  ':',
  '=',
  '&',
  '|',
])

function isFile(path) {
  try {
    return statSync(path).isFile()
  } catch {
    return false
  }
}

function readText(path) {
  try {
    return readFileSync(path, 'utf8')
  } catch {
    return null
  }
}

/** Strip a comment / quotes / backticks from one yaml scalar. */
function scalar(raw) {
  let value = String(raw ?? '').trim()
  const comment = value.search(/\s#/u)
  if (comment !== -1 && !/^['"`]/u.test(value)) value = value.slice(0, comment).trim()
  if (
    (value.startsWith('`') && value.endsWith('`')) ||
    (value.startsWith('"') && value.endsWith('"')) ||
    (value.startsWith("'") && value.endsWith("'"))
  ) {
    value = value.slice(1, -1).trim()
  }
  return value
}

/** `openspec/changes/<id>` when the value points into a change, else null. */
function changeSpec(value) {
  const match = CHANGE_PATH.exec(value)
  if (!match) return null
  const id = match[1]
  if (id === '.' || id === '..') return null
  return `openspec/changes/${id}`
}

function isInside(parent, child) {
  const rel = relative(parent, child)
  return rel !== '' && rel !== '..' && !rel.startsWith(`..${sep}`) && !isAbsolute(rel)
}

/**
 * Parse the tolerant yaml subset used by approval.md: top-level `design:` and
 * `plan:` blocks with scalar `by` / `at` / `sha256` children. A section key is
 * kept even when its block is empty; unknown sections and malformed lines are
 * ignored. Any non-string input yields `{}` — the caller passes null when the
 * file is missing.
 */
export function parseApproval(text) {
  const parsed = {}
  if (typeof text !== 'string' || text === '') return parsed

  let section = null
  for (const rawLine of text.split(/\r?\n/u)) {
    const line = rawLine.replace(/[ \t]+$/u, '')
    if (line.trim() === '' || /^\s*#/u.test(line)) continue

    const top = /^([A-Za-z0-9_-]+)\s*:\s*(.*)$/u.exec(line)
    if (top) {
      // Own-key check, not `in`: a crafted `__proto__:`/`constructor:` line
      // must be ignored instead of touching the prototype.
      const known = Object.prototype.hasOwnProperty.call(SECTION_FIELDS, top[1])
      section = known ? {} : null
      if (section) parsed[top[1]] = section
      continue
    }

    if (section === null) continue
    const child = /^\s+([A-Za-z0-9_-]+)\s*:\s*(.*)$/u.exec(line)
    if (!child) continue
    const value = scalar(child[2])
    if (value !== '') section[child[1]] = value
  }
  return parsed
}

/**
 * Deterministic approval.md text: sections in `design`, `plan` order, fields
 * in a fixed order, one blank line between sections, no trailing spaces, and
 * a final newline. An absent or non-object section is skipped.
 */
export function serializeApproval(parsed) {
  const sections = []
  for (const [section, fields] of Object.entries(SECTION_FIELDS)) {
    const source = parsed?.[section]
    if (!source || typeof source !== 'object') continue
    const lines = [`${section}:`]
    for (const field of fields) {
      const value = source[field]
      if (value === undefined || value === null) continue
      const text = String(value).trim()
      if (text === '') continue
      lines.push(`  ${field}: ${text}`)
    }
    sections.push(lines.join('\n'))
  }
  return sections.length === 0 ? '' : `${sections.join('\n\n')}\n`
}

/**
 * Normalized spec path named by the plan's `**Spec:**` line, or null.
 *
 * Backticks, a markdown link target and a trailing slash are stripped. A path
 * into `openspec/changes/<id>/...` is normalized to `openspec/changes/<id>`;
 * any other path (legacy `docs/superpowers/specs/...`) is returned as written
 * so the caller can reject it explicitly (D-9).
 */
export function extractSpec(content) {
  if (typeof content !== 'string' || content === '') return null
  const match = /^[ \t]*\*\*Spec:\*\*[ \t]*(.+?)[ \t]*$/mu.exec(content)
  if (!match) return null

  let value = match[1].trim()
  const backtick = /^`([^`]+)`/u.exec(value)
  const link = /^\[[^\]]*\]\(([^)]+)\)/u.exec(value)
  if (backtick) value = backtick[1]
  else if (link) value = link[1]
  else value = value.split(/\s+/u)[0]

  value = value
    .trim()
    .replace(/^[`"']+/u, '')
    .replace(/[`"']+$/u, '')
    .replace(/^\.\//u, '')
    .replace(/[/.,;:]+$/u, '')
  if (value === '') return null
  return changeSpec(value) ?? value
}

/**
 * Change id of a spec path: `openspec/changes/<id>(/...)` -> `<id>`.
 * Legacy `docs/superpowers/specs/...` and everything else -> null.
 */
export function resolveChangeFromSpec(specPath) {
  if (typeof specPath !== 'string' || specPath === '') return null
  const change = changeSpec(specPath)
  return change === null ? null : change.slice('openspec/changes/'.length)
}

/**
 * Plan file behind an sdd ledger path: `.superpowers/sdd/<plan-name>(/...)` ->
 * `<repoRoot>/docs/superpowers/plans/<plan-name>.md`, when that file exists.
 */
export function resolvePlanFromSdd(sddPath, repoRoot) {
  if (typeof sddPath !== 'string' || sddPath === '' || !repoRoot) return null
  const match = SDD_PATH.exec(sddPath)
  if (!match) return null
  const name = match[1].replace(/[/.,;:]+$/u, '')
  if (name === '' || name === '.' || name === '..') return null
  const planPath = join(resolve(repoRoot), PLANS_DIR, `${name}.md`)
  return isFile(planPath) ? planPath : null
}

/** sha256 hex of the plan content; '' when the file cannot be read. */
export function hashPlan(planPath) {
  try {
    return createHash('sha256').update(readFileSync(planPath)).digest('hex')
  } catch {
    return ''
  }
}

/**
 * Is the plan approved for its current content (D-10)?
 * Fails with `no plan approval` when the section or its sha256 is missing and
 * with `plan changed after approval` when the hash does not match (a missing
 * plan file is a hash mismatch by construction).
 */
export function planApproved(approval, planPath) {
  const plan = approval?.plan
  if (!plan || typeof plan !== 'object') return { ok: false, reason: PLAN_NO_APPROVAL }
  const expected = typeof plan.sha256 === 'string' ? plan.sha256.trim().toLowerCase() : ''
  if (expected === '') return { ok: false, reason: PLAN_NO_APPROVAL }
  const actual = hashPlan(planPath)
  if (actual === '' || actual !== expected) return { ok: false, reason: PLAN_CHANGED }
  return { ok: true, reason: '' }
}

function readApproval(repoRoot, changeId) {
  return parseApproval(readText(join(repoRoot, CHANGE_DIR, changeId, APPROVAL_FILE)))
}

/**
 * Does approval.md carry a real design approval? An empty `design:` block is
 * treated as no approval (R-4/T1.6f): the section must carry the `by` and `at`
 * scalars `/approve` writes, so a bare header cannot unlock the plan gate.
 */
export function hasDesignApproval(approval) {
  const design = approval?.design
  if (!design || typeof design !== 'object') return false
  return (
    typeof design.by === 'string' &&
    design.by !== '' &&
    typeof design.at === 'string' &&
    design.at !== ''
  )
}

/**
 * Gate A: a plan may only be written for a change whose design is approved.
 * The `**Spec:**` reference is mandatory and must resolve to an openspec
 * change (D-9); a plan written elsewhere is not gated.
 */
export function checkPlanWrite({ filePath, content, repoRoot } = {}) {
  if (typeof filePath !== 'string' || filePath === '') return {}
  const root = resolve(repoRoot || '.')
  const target = resolve(root, filePath)
  if (!isInside(join(root, PLANS_DIR), target)) return {}

  const changeId = resolveChangeFromSpec(extractSpec(content))
  if (changeId === null) return { deny: SPEC_DENY }
  if (!hasDesignApproval(readApproval(root, changeId))) {
    return { deny: `design not approved; run /approve ${changeId} design` }
  }
  return {}
}

/**
 * Gate C: `approval.md` is written only by `/approve`, never by a tool (D-1).
 * Applies wherever the file lives, not only inside a change directory.
 */
export function checkApprovalWrite({ filePath, repoRoot } = {}) {
  if (typeof filePath !== 'string' || filePath === '') return {}
  const target = resolve(resolve(repoRoot || '.'), filePath)
  if (basename(target) === APPROVAL_FILE) return { deny: APPROVAL_DENY }
  return {}
}

function tokenStart(text, index) {
  let start = index
  while (start > 0 && !TOKEN_STOP.has(text[start - 1])) start -= 1
  return start
}

/**
 * All plan references in one string, in textual order: a direct
 * `docs/superpowers/plans/x.md` path (absolute or repository-relative) or an
 * `.superpowers/sdd/x/` ledger path. Empty when the string references none.
 */
function planReferences(text) {
  if (typeof text !== 'string' || text === '') return []
  const found = []

  for (let at = text.indexOf(DIRECT_PREFIX); at !== -1; at = text.indexOf(DIRECT_PREFIX, at + 1)) {
    const match = DIRECT_PLAN.exec(text.slice(at))
    if (!match) continue
    const start = tokenStart(text, at)
    found.push({ index: at, path: text.slice(start, at + match[0].length) })
  }

  for (let at = text.indexOf(SDD_PREFIX); at !== -1; at = text.indexOf(SDD_PREFIX, at + 1)) {
    const match = SDD_PATH.exec(text.slice(at))
    if (!match) continue
    const name = match[1].replace(/[/.,;:]+$/u, '')
    if (name !== '' && name !== '.' && name !== '..') found.push({ index: at, name })
  }

  return found.sort((left, right) => left.index - right.index)
}

/** Deny text for an unapproved plan; `<id>` stays literal when unknown. */
function denyPlanNotApproved(changeId) {
  return { deny: `plan not approved; run /approve ${changeId ?? '<id>'} plan` }
}

/** Plan path a parsed reference points to (the file may be missing). */
function referencePlanPath(reference, repoRoot) {
  if (typeof reference.name === 'string') {
    return (
      resolvePlanFromSdd(`${SDD_PREFIX}${reference.name}`, repoRoot) ??
      join(repoRoot, PLANS_DIR, `${reference.name}.md`)
    )
  }
  return isAbsolute(reference.path) ? resolve(reference.path) : resolve(repoRoot, reference.path)
}

/**
 * Full gate-B chain for one referenced plan: read it, take its `**Spec:**`,
 * resolve the change, verify the plan approval against the file content.
 * Missing/spec-less plans fail closed.
 */
function planVerdict(repoRoot, planPath) {
  const content = readText(planPath)
  if (content === null) return denyPlanNotApproved()
  const changeId = resolveChangeFromSpec(extractSpec(content))
  if (changeId === null) return denyPlanNotApproved()

  const verdict = planApproved(readApproval(repoRoot, changeId), planPath)
  if (verdict.ok) return {}
  if (verdict.reason === PLAN_NO_APPROVAL) return denyPlanNotApproved(changeId)
  return { deny: PLAN_CHANGED_DENY }
}

/**
 * Gate B: a dispatch may only start when every plan it references is approved
 * for its current content (D-10). The check covers the prompt and, when
 * given, the workflow script; the first failing reference denies, so an
 * approved plan cannot mask a later unapproved one. No plan reference at all
 * means no gate.
 */
export function checkDispatch({ prompt, script, repoRoot } = {}) {
  const root = resolve(repoRoot || '.')
  const references = [...planReferences(prompt), ...planReferences(script)]
  for (const reference of references) {
    const verdict = planVerdict(root, referencePlanPath(reference, root))
    if (verdict.deny !== undefined) return verdict
  }
  return {}
}

/**
 * Gate B for Mode 1 starts: a write under `.superpowers/sdd/<plan-name>/`
 * (ledger, briefs) is allowed only when that plan is approved for its current
 * content (D-7). A missing plan file fails closed with `plan not found`.
 */
export function checkSddWrite({ filePath, repoRoot } = {}) {
  if (typeof filePath !== 'string' || filePath === '') return {}
  const root = resolve(repoRoot || '.')
  const target = resolve(root, filePath)
  const sddDir = join(root, SDD_DIR)
  if (!isInside(sddDir, target)) return {}

  const segments = relative(sddDir, target).split(sep)
  if (segments.length < 2) return {}
  const name = segments[0]
  if (name === '' || name === '.' || name === '..') return {}

  const planPath = resolvePlanFromSdd(`${SDD_PREFIX}${name}`, root)
  if (planPath === null) return { deny: `plan not found: ${name}` }
  return planVerdict(root, planPath)
}

/**
 * Gates A and C for a list of absolute write targets (from
 * `harness_target.py targets`). First denial wins. A target under plans/ has
 * no content here, so it can never carry a `**Spec:**` line and is denied —
 * exactly the bash-heredoc case the tool-level gates would otherwise miss.
 */
export function checkBashTargets(targets, repoRoot) {
  if (!Array.isArray(targets)) return {}
  const root = resolve(repoRoot || '.')
  for (const raw of targets) {
    if (typeof raw !== 'string' || raw === '') continue
    const target = resolve(root, raw)
    const approval = checkApprovalWrite({ filePath: target, repoRoot: root })
    if (approval.deny !== undefined) return approval
    const plan = checkPlanWrite({ filePath: target, content: null, repoRoot: root })
    if (plan.deny !== undefined) return plan
  }
  return {}
}