/**
 * Kernel extension registry resolver: duplicate detection, capability conflicts,
 * dependency ordering (topological sort), optional signer/hash policy, and cycle reporting.
 *
 * Enforcement at boot remains in `kernel/init.js` (`kernel.ext.d`); this module provides
 * shared deterministic resolution for booter tooling, tests, and strict preflight.
 *
 * **Keep in sync:** `topologicalOrderKernelExtensions` / `kernelExtensionDependencyDepth`
 * must match `topologicalOrderKernelExtEntries` / `kernelExtDependencyDepth` in
 * `kernel/lib/init/init-main.js` (same Kahn sort and depth walk). CI: booter test
 * `kernel extension topological order matches resolver module`.
 */

/**
 * @param {{ extId: string, source: string }[]} entries
 * @returns {{ ok: true, ordered: typeof entries } | { ok: false, duplicateIds: string[] }}
 */
export function resolveKernelExtensionIds(entries) {
  const seen = new Map()
  /** @type {string[]} */
  const dups = []
  for (const e of entries) {
    const id = String(e.extId || '').trim()
    if (!id) continue
    if (seen.has(id)) dups.push(id)
    else seen.set(id, e.source)
  }
  if (dups.length) return { ok: false, duplicateIds: [...new Set(dups)] }
  return { ok: true, ordered: [...entries] }
}

/**
 * @param {{ extId: string, capabilities?: string[] }[]} entries
 * @returns {{ ok: boolean, conflicts: string[] }}
 */
/**
 * Optional `provides` rows declare a logical service name + version string per extension drop-in.
 * Two different extension ids claiming the same `name` with different `version` values is a strict conflict.
 * @param {{ extId: string, provides?: { name?: string, version?: string, semver?: string }[] }[]} entries
 * @returns {{ ok: boolean, conflicts: string[] }}
 */
export function detectKernelExtensionProvidesConflicts(entries) {
  /** @type {Map<string, { extId: string, version: string }>} */
  const byName = new Map()
  /** @type {string[]} */
  const conflicts = []
  for (const e of entries) {
    const id = String(e.extId || '').trim()
    if (!id) continue
    const provides = Array.isArray(e.provides) ? e.provides : []
    for (const p of provides) {
      if (!p || typeof p !== 'object') continue
      const name = String(p.name || '').trim()
      const ver = String(p.version ?? p.semver ?? '').trim()
      if (!name || !ver) continue
      const prev = byName.get(name)
      if (prev && prev.version !== ver) {
        conflicts.push(`${name}: ${prev.extId}@${prev.version} vs ${id}@${ver}`)
      } else if (!prev) {
        byName.set(name, { extId: id, version: ver })
      }
    }
  }
  conflicts.sort()
  return { ok: conflicts.length === 0, conflicts }
}

export function detectKernelExtensionCapabilityConflicts(entries) {
  /** @type {Map<string, string>} */
  const capToId = new Map()
  /** @type {string[]} */
  const conflicts = []
  for (const e of entries) {
    const id = String(e.extId || '').trim()
    if (!id) continue
    const caps = Array.isArray(e.capabilities)
      ? e.capabilities.map((c) => String(c).trim()).filter(Boolean)
      : []
    for (const c of caps) {
      const prev = capToId.get(c)
      if (prev && prev !== id) conflicts.push(`${c}(${prev} vs ${id})`)
      else capToId.set(c, id)
    }
  }
  return { ok: conflicts.length === 0, conflicts }
}

/**
 * @param {{ file: string, extId: string, scripts: string[], dependsOn: string[], beforeIds?: string[], signaturePointer?: string, signerPubHex?: string, contentSha256Hex?: string }[]} entries
 * @returns {{ ok: true, ordered: typeof entries } | { ok: false, cycleExtIds: string[] }}
 */
export function topologicalOrderKernelExtensions(entries) {
  const sorted = [...entries].sort((a, b) => a.file.localeCompare(b.file))
  const idToFile = new Map()
  for (const e of sorted) {
    if (!idToFile.has(e.extId)) idToFile.set(e.extId, e.file)
  }
  /** @type {Map<string, string[]>} */
  const adj = new Map()
  /** @type {Map<string, number>} */
  const indeg = new Map()
  for (const e of sorted) indeg.set(e.file, 0)
  for (const e of sorted) {
    for (const dep of e.dependsOn) {
      const from = idToFile.get(dep)
      if (!from || from === e.file) continue
      if (!adj.has(from)) adj.set(from, [])
      adj.get(from).push(e.file)
      indeg.set(e.file, (indeg.get(e.file) || 0) + 1)
    }
  }
  /** @type {string[]} */
  const q = sorted
    .map((e) => e.file)
    .filter((f) => (indeg.get(f) || 0) === 0)
    .sort()
  /** @type {string[]} */
  const out = []
  while (q.length) {
    const f = q.shift()
    if (!f) break
    out.push(f)
    for (const to of adj.get(f) || []) {
      indeg.set(to, (indeg.get(to) || 0) - 1)
      if (indeg.get(to) === 0) {
        q.push(to)
        q.sort()
      }
    }
  }
  if (out.length !== sorted.length) {
    const stuck = sorted.filter((e) => !out.includes(e.file))
    return { ok: false, cycleExtIds: stuck.map((e) => e.extId) }
  }
  const byFile = new Map(sorted.map((e) => [e.file, e]))
  return {
    ok: true,
    ordered: out.map((f) => byFile.get(f)).filter(Boolean)
  }
}

/**
 * @param {{ extId: string, dependsOn: string[] }[]} entries
 * @returns {number}
 */
export function kernelExtensionDependencyDepth(entries) {
  const idToEntry = new Map(entries.map((e) => [e.extId, e]))
  const memo = new Map()
  /**
   * @param {string} id
   * @param {Set<string>} stack
   */
  function depth(id, stack) {
    if (memo.has(id)) return memo.get(id)
    if (stack.has(id)) return 99
    const e = idToEntry.get(id)
    if (!e) return 0
    stack.add(id)
    let d = 0
    for (const dep of e.dependsOn) {
      d = Math.max(d, depth(dep, stack) + 1)
    }
    stack.delete(id)
    memo.set(id, d)
    return d
  }
  let max = 0
  for (const e of entries) {
    max = Math.max(max, depth(e.extId, new Set()))
  }
  return max
}

/**
 * @param {Record<string, string | string[] | undefined>} pins extId → expected ed25519 pubkey hex (64) or list for threshold
 * @param {{ extId: string, signerPubHex?: string }[]} entries
 * @returns {{ ok: boolean, violations: string[] }}
 */
export function validateExtensionSignerPins(entries, pins) {
  if (!pins || typeof pins !== 'object') return { ok: true, violations: [] }
  /** @type {string[]} */
  const violations = []
  for (const e of entries) {
    const id = String(e.extId || '').trim()
    if (!id) continue
    const need = pins[id]
    if (need == null) continue
    const needList = Array.isArray(need)
      ? need.map((x) => String(x).trim().toLowerCase())
      : [String(need).trim().toLowerCase()]
    const got = String(e.signerPubHex || '').trim().toLowerCase()
    if (!got || got.length !== 64 || !/^[0-9a-f]+$/.test(got)) {
      violations.push(`${id}: missing or invalid signerPubHex`)
      continue
    }
    if (!needList.includes(got)) {
      violations.push(`${id}: signer pin mismatch`)
    }
  }
  return { ok: violations.length === 0, violations }
}

/**
 * @param {Record<string, string>} hashPins extId → lowercase sha256 hex
 * @param {{ extId: string, contentSha256Hex?: string }[]} entries
 * @returns {{ ok: boolean, violations: string[] }}
 */
export function validateExtensionContentHashes(entries, hashPins) {
  if (!hashPins || typeof hashPins !== 'object') return { ok: true, violations: [] }
  /** @type {string[]} */
  const violations = []
  for (const e of entries) {
    const id = String(e.extId || '').trim()
    if (!id) continue
    const need = hashPins[id]
    if (need == null) continue
    const want = String(need).trim().toLowerCase()
    const got = String(e.contentSha256Hex || '').trim().toLowerCase()
    if (!got || got !== want) violations.push(`${id}: content hash pin mismatch`)
  }
  return { ok: violations.length === 0, violations }
}

/**
 * Full resolve pipeline for extension drop-in rows (same shape as kernel `kernel.ext.d` JSON + file meta).
 * @param {{ file: string, extId: string, scripts: string[], dependsOn: string[], beforeIds?: string[], signaturePointer?: string, signerPubHex?: string, contentSha256Hex?: string, capabilities?: string[], provides?: { name?: string, version?: string, semver?: string }[] }[]} entries
 * @param {{ signerPins?: Record<string, string | string[]>, hashPins?: Record<string, string>, maxDepth?: number } | undefined} policy
 */
export function resolveKernelExtensionsFull(entries, policy = {}) {
  const idRes = resolveKernelExtensionIds(
    entries.map((e) => ({ extId: e.extId, source: e.file }))
  )
  if (!idRes.ok) {
    return {
      ok: false,
      reason: 'duplicate_ids',
      duplicateIds: idRes.duplicateIds,
      ordered: []
    }
  }
  const capRes = detectKernelExtensionCapabilityConflicts(entries)
  if (!capRes.ok) {
    return {
      ok: false,
      reason: 'capability_conflict',
      conflicts: capRes.conflicts,
      ordered: []
    }
  }
  const provRes = detectKernelExtensionProvidesConflicts(entries)
  if (!provRes.ok) {
    return {
      ok: false,
      reason: 'provides_conflict',
      conflicts: provRes.conflicts,
      ordered: []
    }
  }
  const maxDepth = policy.maxDepth
  if (typeof maxDepth === 'number' && maxDepth >= 1) {
    const d = kernelExtensionDependencyDepth(
      entries.map((e) => ({ extId: e.extId, dependsOn: e.dependsOn || [] }))
    )
    if (d > maxDepth) {
      return {
        ok: false,
        reason: 'max_depth',
        depth: d,
        maxDepth,
        ordered: []
      }
    }
  }
  const pinRes = validateExtensionSignerPins(entries, policy.signerPins || {})
  if (!pinRes.ok) {
    return {
      ok: false,
      reason: 'signer_pins',
      violations: pinRes.violations,
      ordered: []
    }
  }
  const hashRes = validateExtensionContentHashes(entries, policy.hashPins || {})
  if (!hashRes.ok) {
    return {
      ok: false,
      reason: 'hash_pins',
      violations: hashRes.violations,
      ordered: []
    }
  }
  const topo = topologicalOrderKernelExtensions(entries)
  if (!topo.ok) {
    return {
      ok: false,
      reason: 'cycle',
      cycleExtIds: topo.cycleExtIds,
      ordered: []
    }
  }
  return { ok: true, ordered: topo.ordered, reason: null }
}