// implement-loop — the per-task implement loop, as a Workflow script.
//
// This is the Workflow-substrate form of what used to be the
// `implement-orchestrator` agent's inline three-phase role-switch loop.
// The substrate change is the point of issue #7's Part B:
//
//   • Each per-task phase is now a separate `agent()` call — implementer,
//     spec-reviewer, quality-reviewer are dispatched as their existing
//     agent-types (they SURVIVE the migration; the inline-role-switch
//     ORCHESTRATOR is what retires). A single phase is therefore
//     independently invokable, which the inline loop could not offer.
//   • Inter-phase aggregation and the re-loop limit are deterministic
//     code here, not natural-language reasoning between dispatches.
//   • Routing keys on the structured verdict each agent reports (which
//     encodes the project's real build/test outcome), not on a guess.
//
// Discipline preserved verbatim from the old loop:
//   • The script NEVER commits and NEVER moves main HEAD. All code edits,
//     the stats file, and (on PARTIAL/BLOCKED) BLOCKED.md live in the
//     working tree as unstaged changes; the orchestrator that invoked
//     this workflow inspects and commits.
//   • Tasks run SEQUENTIALLY — plan tasks carry implicit ordering
//     dependencies, and the script does not know the graph, so a BLOCKED
//     task stops the loop rather than skipping ahead.
//   • Spec-compliance is gated BEFORE quality, per task.
//   • Re-loop limit: 2 repair retries per failure-mode per task; the 3rd
//     unresolved attempt escalates to BLOCKED.
//   • Quality re-loop hold (issue #10): a quality finding whose only remedy
//     would contradict the ratified plan (a name/signature/structure the
//     task prescribes) is HELD, not chased into a deviation the next review
//     then re-flags. The repair implementer keeps the plan and records the
//     finding in `held`; a no-op backstop holds it anyway when a repair
//     leaves the diff unchanged (or cycles back) yet quality still flags.
//     Either way the finding surfaces as a concern, not a false BLOCKED on a
//     green task — and the orchestrator weighs it on its Step-3 inspection.
//     A finding the implementer judges correctness-breaking (would not
//     build / a test fails / a prescribed caller breaks) escalates to
//     BLOCKED instead of holding. The held/no-op partition is the
//     implementer's call, not enforced in code (the script cannot tell a
//     cosmetic hold from an ignored bug) — hence the neutral concern label
//     and the orchestrator backstop, same trust placed in its other reports.
//   • The script has no filesystem or shell access of its own — every
//     working-tree mutation (code, stats.json, BLOCKED.md) happens inside
//     an agent() call.
//
// Carrier — passed as the Workflow `args` object by the orchestrator:
//   mode:          'standard' | 'mini'
//   iter_id:       e.g. 'ct.2.3' (standard) or 'bugfix-<symptom>' / 'feat-<behaviour>' (mini)
//   plan_path:     (standard) path under docs/plans
//   task_range:    (standard, optional) [from, to] inclusive, 1-based
//   red_test_path: (mini) absolute path to the RED test from debug / tdd
//   cause_summary: (mini) 1–2 sentences (debugger cause, or tdd spec_summary)
//   constraint:    (mini) e.g. 'minimal fix, no surrounding cleanup'

export const meta = {
  name: 'implement-loop',
  description:
    'Execute a plan iteration (standard) or a debug/tdd RED->GREEN handoff (mini) task-by-task: implementer -> spec-compliance -> quality, with deterministic re-loop and aggregation. Writes code, tests, stats.json, and (on PARTIAL/BLOCKED) BLOCKED.md to the working tree as unstaged changes; never commits, never moves main HEAD.',
  phases: [
    { title: 'Preflight' },
    { title: 'Per-task loop' },
    { title: 'E2E coverage' },
    { title: 'Report' },
  ],
}

const {
  mode = 'standard',
  iter_id,
  plan_path,
  task_range = null,
  red_test_path,
  cause_summary,
  constraint = 'minimal change, no surrounding cleanup',
} = args || {}

const STANDING =
  "Standing reading first (the plugin convention): read the project's CLAUDE.md " +
  '(its "## Skills plugin: project facts" name the build and test commands and any ' +
  'design ledger) and `git log -10 --format=full`. Resolve the build/test commands ' +
  'from those facts — do not assume a toolchain.'

// JSON Schemas — force structured verdicts so the script can branch on real outcomes.
const PREFLIGHT_SCHEMA = {
  type: 'object',
  additionalProperties: false,
  required: ['clean', 'head_sha', 'branch'],
  properties: {
    clean: { type: 'boolean', description: '`git status --porcelain` produced no output' },
    head_sha: { type: 'string' },
    branch: { type: 'string' },
    dirty_paths: { type: 'array', items: { type: 'string' } },
  },
}
const TASKS_SCHEMA = {
  type: 'object',
  additionalProperties: false,
  required: ['tasks'],
  properties: {
    tasks: {
      type: 'array',
      items: {
        type: 'object',
        additionalProperties: false,
        required: ['id', 'title', 'text'],
        properties: {
          id: { type: 'integer' },
          title: { type: 'string' },
          text: { type: 'string', description: 'verbatim task block from the plan' },
        },
      },
    },
  },
}
const IMPL_SCHEMA = {
  type: 'object',
  additionalProperties: false,
  required: ['status', 'summary'],
  properties: {
    status: { type: 'string', enum: ['DONE', 'DONE_WITH_CONCERNS', 'NEEDS_CONTEXT', 'BLOCKED'] },
    summary: { type: 'string', description: 'one line: what changed (paths + functions)' },
    concerns: { type: 'array', items: { type: 'string' } },
    reason: { type: 'string', description: 'on BLOCKED/NEEDS_CONTEXT: the blocker' },
    held: {
      type: 'array',
      description:
        'quality-repair dispatch only: quality findings KEPT against the ratified plan because honouring them ' +
        'would deviate from a plan-prescribed name/signature/structure while the tree stays green. Each is a ' +
        'concern to surface, not a deviation to chase. A finding that would break correctness is NOT held — it ' +
        'is escalated via status BLOCKED.',
      items: {
        type: 'object',
        additionalProperties: false,
        required: ['finding', 'kept', 'why'],
        properties: {
          finding: { type: 'string', description: 'the quality finding being kept (held)' },
          kept: { type: 'string', description: 'the plan-prescribed element preserved (name/signature/structure)' },
          why: { type: 'string', description: 'why honouring the finding would contradict the ratified plan' },
        },
      },
    },
  },
}
const SPEC_SCHEMA = {
  type: 'object',
  additionalProperties: false,
  required: ['status'],
  properties: {
    status: { type: 'string', enum: ['compliant', 'non_compliant', 'unclear', 'infra_blocked'] },
    findings: { type: 'array', items: { type: 'string' }, description: 'missing requirements + unrequested extras' },
    ambiguity: { type: 'string' },
  },
}
const QUAL_SCHEMA = {
  type: 'object',
  additionalProperties: false,
  required: ['status', 'diff_fingerprint'],
  properties: {
    status: { type: 'string', enum: ['approved', 'changes_requested', 'infra_blocked'] },
    issues: { type: 'array', items: { type: 'string' }, description: 'Important + Minor only (Nits never gate)' },
    diff_fingerprint: {
      type: 'string',
      description:
        'sha256 hex of the FULL `git diff HEAD` (the whole working-tree diff, not a footprint subset) — REQUIRED; ' +
        'the loop compares it across rounds to detect a no-op/cyclic repair and stop oscillating to a false BLOCKED',
    },
  },
}
const E2E_SCHEMA = {
  type: 'object',
  additionalProperties: false,
  required: ['status'],
  properties: {
    status: { type: 'string', enum: ['DONE', 'DONE_WITH_CONCERNS', 'NEEDS_CONTEXT', 'BLOCKED'] },
    fixtures: { type: 'array', items: { type: 'string' } },
    note: { type: 'string' },
  },
}
const FINALIZE_SCHEMA = {
  type: 'object',
  additionalProperties: false,
  required: ['stats_path', 'wrote_blocked_md'],
  properties: {
    stats_path: { type: 'string' },
    wrote_blocked_md: { type: 'boolean' },
    files_touched: { type: 'integer' },
  },
}

// ---- Phase 0 — clean-tree preflight ------------------------------------
phase('Preflight')
const pre = await agent(
  `${STANDING}\n\nYou are the clean-tree preflight for an implement iteration. ` +
    'Run `git status --porcelain`, `git rev-parse HEAD`, and `git rev-parse --abbrev-ref HEAD`. ' +
    'Report whether the tree is clean (no porcelain output), the HEAD sha, the branch, and any dirty paths. ' +
    'Do NOT modify anything, do NOT commit. The HEAD sha is an informational anchor only — never a reset target.',
  { label: 'preflight', phase: 'Preflight', schema: PREFLIGHT_SCHEMA },
)
if (!pre) return { status: 'BLOCKED', iter_id, reason: 'infra: preflight agent did not return' }
if (!pre.clean) {
  return {
    status: 'BLOCKED',
    iter_id,
    reason: 'infra: working tree dirty — the orchestrator must clean it before re-invoking',
    dirty_paths: pre.dirty_paths || [],
  }
}
const startSha = pre.head_sha

// ---- Phase 1 — assemble the task list ----------------------------------
let tasks
if (mode === 'mini') {
  tasks = [
    {
      id: 1,
      title: 'drive the RED test to GREEN',
      text:
        `Make this RED test pass: ${red_test_path}\n\n` +
        `Context (debugger cause, or tdd spec_summary): ${cause_summary}\n\n` +
        `Constraint: ${constraint}`,
    },
  ]
} else {
  const extracted = await agent(
    `${STANDING}\n\nRead the plan at ${plan_path}. Extract ` +
      (task_range ? `tasks ${task_range[0]}..${task_range[1]} (inclusive, 1-based)` : 'every task') +
      ', each as its VERBATIM block with the task id and a one-line title. Do not summarise or reorder. Do not edit anything.',
    { label: 'plan-extract', phase: 'Per-task loop', schema: TASKS_SCHEMA },
  )
  if (!extracted || !extracted.tasks || extracted.tasks.length === 0) {
    return { status: 'NEEDS_CONTEXT', iter_id, reason: `no tasks extracted from ${plan_path}` }
  }
  tasks = extracted.tasks
}

// ---- Phase 2 — per-task loop (sequential) ------------------------------
phase('Per-task loop')

async function runTask(task) {
  // 2.1 — implementer phase
  const impl = await agent(
    `${STANDING}\n\nImplement this task exactly, RED-first if it adds behaviour (TDD is an independent ` +
      'inner-loop discipline — add the failing test inline even if the task text forgot to script it). ' +
      'Build and test must be green before you report DONE. Leave all edits UNSTAGED; never commit.\n\n' +
      `mode: ${mode}\niter_id: ${iter_id}\n\nTASK ${task.id} — ${task.title}\n${task.text}`,
    { agentType: 'implementer', label: `impl:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
  )
  if (!impl) return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: 'implementer agent did not return' }
  if (impl.status === 'BLOCKED') return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: impl.reason || 'worker-blocked' }
  if (impl.status === 'NEEDS_CONTEXT') return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: `context-exhausted: ${impl.reason || ''}` }
  const concerns = impl.concerns || []

  // 2.2 — spec-compliance check (gated before quality), with repair re-loop
  for (let round = 0; ; round++) {
    const spec = await agent(
      `${STANDING}\n\nSpec-compliance review of task ${task.id}. Compare \`git diff HEAD\` against the task ` +
        'text ONLY — list missing requirements and unrequested extras. No quality opinions, no fix proposals. ' +
        `Focus on the files this task claims to touch.\n\nTASK ${task.id} — ${task.title}\n${task.text}`,
      { agentType: 'spec-reviewer', label: `spec:${task.id}`, phase: 'Per-task loop', schema: SPEC_SCHEMA },
    )
    if (spec && spec.status === 'compliant') break
    if (spec && spec.status === 'unclear') return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: 'spec-ambiguous', detail: spec.ambiguity }
    if (round >= 2) return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: 'review-loop-exhausted (spec-compliance)' }
    // repair: re-dispatch the implementer with the review findings as the repair brief
    await agent(
      `${STANDING}\n\nRepair task ${task.id} to satisfy the spec-compliance review. Address EACH finding; ` +
        'do not widen scope. Keep build + tests green; leave edits unstaged.\n\n' +
        `TASK ${task.id} — ${task.title}\n${task.text}\n\nFINDINGS:\n- ${(spec?.findings || ['(none reported)']).join('\n- ')}`,
      { agentType: 'implementer', label: `impl-fix-spec:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
    )
  }

  // 2.3 — quality check, with repair re-loop.
  // The plan-vs-finding judgement lives here, with the implementer that holds
  // the task text — the quality-reviewer is deliberately blind to it. The hold
  // is keyed on two structural signals, never on a self-reported status enum
  // (which the implementer's contract overloads): the `held` array the repair
  // returns, and a no-op backstop (a changes_requested verdict over a diff
  // whose fingerprint was already reviewed-and-flagged this task means the
  // intervening repair changed nothing or cycled back, so re-running quality
  // is futile).
  let heldConcerns = []
  const seenFingerprints = new Set()
  for (let round = 0; ; round++) {
    const qual = await agent(
      `${STANDING}\n\nQuality review of task ${task.id} (spec-compliance is already green — do not re-check it). ` +
        'Read every chunk of `git diff HEAD` in this task\'s footprint. Report only Important and Minor issues; ' +
        'Nits never gate. Also report `diff_fingerprint` (REQUIRED): the sha256 hex of the FULL `git diff HEAD` ' +
        '(`git diff HEAD | sha256sum` — the whole working-tree diff, NOT narrowed to this task\'s footprint). ' +
        'The loop compares it across rounds to detect a no-op/cyclic repair.',
      { agentType: 'quality-reviewer', label: `qual:${task.id}`, phase: 'Per-task loop', schema: QUAL_SCHEMA },
    )
    if (qual && qual.status === 'approved') break
    // No-op / cyclic-repair backstop: a changes_requested verdict over a diff-state already reviewed-and-flagged
    // this task means the intervening repair changed nothing (or cycled back to an earlier state) — the
    // implementer kept the plan, or rejected the finding. Re-running quality would only re-flag identical code,
    // so stop here rather than burning the retry budget down to a false BLOCKED. A byte-identical diff cannot
    // distinguish a principled plan-hold from an ignored finding, so the concern is labelled neutrally and left
    // for the orchestrator to adjudicate on its Step-3 inspection.
    if (qual && qual.status === 'changes_requested' && qual.diff_fingerprint && seenFingerprints.has(qual.diff_fingerprint)) {
      heldConcerns = (qual.issues && qual.issues.length ? qual.issues : ['(finding not reported)']).map(
        (i) =>
          'unresolved quality finding — the repair left the diff unchanged (a kept plan-prescribed element, or a ' +
          `finding the implementer rejected); verify by hand on inspection: ${i}`,
      )
      break
    }
    if (round >= 2) return { id: task.id, title: task.title, outcome: 'BLOCKED', reason: 'review-loop-exhausted (quality)' }
    if (qual && qual.diff_fingerprint) seenFingerprints.add(qual.diff_fingerprint)
    const fix = await agent(
      `${STANDING}\n\nThe quality review of task ${task.id} requested changes. Address EACH Important/Minor issue; ` +
        'do not widen scope; keep build + tests green; leave edits unstaged. The task text below is the ratified plan.\n\n' +
        'HOLD CLAUSE — most issues you simply fix. But if honouring an issue would force you to deviate from a ' +
        'name, signature, or structure THIS TASK prescribes (or to break the downstream callers the plan ' +
        'prescribes), do NOT deviate. Two cases:\n' +
        '  • The finding is cosmetic — keeping the plan leaves the build and tests GREEN (e.g. a name reads ' +
        'slightly off but everything compiles and passes). KEEP the plan, fix every other issue, and record each ' +
        'kept finding in `held` (finding / kept / why). Do not rename or restructure to chase it.\n' +
        '  • Honouring the plan would make the code WRONG — it would not build, a test would fail, or a ' +
        'prescribed caller would break. That is a real plan-vs-correctness conflict, not a cosmetic hold: report ' +
        'status BLOCKED with the conflict in `reason`. Never bury a correctness defect in `held`.\n' +
        'A finding whose only remedy is to diverge from the ratified plan must be held or escalated, never chased ' +
        'into a deviation the next review flags.\n\n' +
        `TASK ${task.id} — ${task.title}\n${task.text}\n\nISSUES:\n- ` + (qual?.issues || ['(none reported)']).join('\n- '),
      { agentType: 'implementer', label: `impl-fix-qual:${task.id}`, phase: 'Per-task loop', schema: IMPL_SCHEMA },
    )
    if (fix && (fix.status === 'BLOCKED' || fix.status === 'NEEDS_CONTEXT')) {
      // The implementer judged a finding a real plan-vs-correctness conflict. Escalate loudly so it is
      // adjudicated, rather than letting that judgement ride a green commit as a quiet concern.
      return {
        id: task.id,
        title: task.title,
        outcome: 'BLOCKED',
        reason: `quality/plan conflict: ${fix.reason || 'honouring a quality finding would break the ratified plan'}`,
      }
    }
    if (fix && fix.held && fix.held.length) {
      // The implementer kept plan-prescribed elements against cosmetic findings. Stop chasing — re-running
      // quality would only re-flag the unchanged code. Surface the held findings as concerns to weigh.
      heldConcerns = fix.held.map(
        (h) => `quality finding held against the ratified plan: ${h.finding} — kept ${h.kept}; honouring it would ${h.why}`,
      )
      break
    }
  }

  return { id: task.id, title: task.title, outcome: 'DONE', concerns: [...concerns, ...heldConcerns] }
}

const results = []
for (const task of tasks) {
  const r = await runTask(task)
  results.push(r)
  if (r.outcome === 'BLOCKED') break // do not skip ahead — task ordering dependencies are unknown
}

const completed = results.filter((r) => r.outcome === 'DONE')
const blocked = results.find((r) => r.outcome === 'BLOCKED')
let outcome
if (!blocked) outcome = 'DONE'
else if (completed.length > 0) outcome = 'PARTIAL'
else outcome = 'BLOCKED'

// ---- Phase 3 — E2E coverage (standard mode, only on a full clean run) --
let e2e = null
if (mode === 'standard' && outcome === 'DONE') {
  phase('E2E coverage')
  e2e = await agent(
    `${STANDING}\n\nThe iteration completed. Identify 1–3 invariants worth protecting and write the smallest ` +
      'E2E fixtures for them in the project\'s canonical fixture form; each test\'s doc comment names the property ' +
      'it protects. Run the project\'s test command — all green. Leave edits unstaged; never commit.\n\n' +
      `iter_id: ${iter_id}\nshipped: ${completed.map((c) => `#${c.id} ${c.title}`).join('; ')}`,
    { agentType: 'tester', label: 'e2e', phase: 'E2E coverage', schema: E2E_SCHEMA },
  )
}

// ---- Phase 4/5 — finalize: stats.json always, BLOCKED.md on non-DONE ----
phase('Report')
const aggregate = {
  iter_id,
  mode,
  started_from: startSha,
  outcome,
  tasks_total: tasks.length,
  tasks_completed: completed.length,
  task_summaries: results.map((r) => ({ id: r.id, title: r.title, outcome: r.outcome })),
  concerns: results.flatMap((r) => r.concerns || []),
  blocked_detail: blocked ? { task: blocked.id, reason: blocked.reason, detail: blocked.detail || null } : null,
}

const fin = await agent(
  `${STANDING}\n\nFinalize an implement iteration. Using the aggregate below:\n` +
    '1. Write a stats file at `/tmp/iter-' + iter_id + '/stats.json` (or under the project stats dir if its facts ' +
    'declare one) containing: iter_id, date (from `date +%F`), mode, outcome, tasks_total, tasks_completed, and ' +
    'blocked_reason (or null).\n' +
    (outcome === 'DONE'
      ? '2. Do NOT write BLOCKED.md — this run is DONE.\n'
      : '2. Write `BLOCKED.md` at the repo ROOT (uncommitted by convention; never staged). Sections: a `# BLOCKED — ' +
        'iter ' + iter_id + '` header with Date/Started-from/Status/Tasks-completed, `## What ran` (one line per DONE ' +
        'task), `## What did not` (the blocked task, its reason, and a one-line suggested next step), `## Concerns`, ' +
        'and `## Files touched` (from `git diff --name-only HEAD`).\n') +
    'Report the stats path, whether you wrote BLOCKED.md, and the count from `git diff --name-only HEAD | wc -l`. ' +
    'Do NOT commit anything.\n\nAGGREGATE:\n' + JSON.stringify(aggregate, null, 2),
  { label: 'finalize', phase: 'Report', schema: FINALIZE_SCHEMA },
)

// ---- End-report — the orchestrator reads this, inspects the tree, commits.
return {
  status: outcome,
  iter_id,
  mode,
  started_from: startSha,
  tasks_total: tasks.length,
  tasks_completed: completed.length,
  task_summaries: aggregate.task_summaries,
  concerns: aggregate.concerns,
  e2e_fixtures: e2e ? e2e.fixtures || [] : [],
  stats_path: fin ? fin.stats_path : null,
  blocked_md: fin && fin.wrote_blocked_md ? 'BLOCKED.md (uncommitted)' : null,
  files_touched: fin ? fin.files_touched : null,
  blocked_detail: aggregate.blocked_detail,
}