/**
 * Strategist role — rewrites HOW only; must NOT rewrite acceptance criteria.
 */

export interface StrategistPromptInput {
  objective: string;
  planMarkdown: string;
  gaps: string[];
  historyNotes?: string;
}

/**
 * Build a strategist prompt. Structural HOW changes only — plan contract is frozen.
 */
export function buildStrategistPrompt(input: StrategistPromptInput): string {
  const gapList =
    input.gaps.length > 0
      ? input.gaps.map((g, i) => `${i + 1}. ${g}`).join("\n")
      : "(none listed)";

  const history = input.historyNotes?.trim()
    ? input.historyNotes
    : "(no additional history notes)";

  return [
    "You are the Goal Strategist for the pi-goal-expander harness.",
    "The implementer has failed verification several rounds in a row.",
    "Diagnose WHY it is stuck and recommend ONE concrete STRUCTURAL change to the HOW.",
    "",
    "## Hard constraints",
    "",
    "- You MUST NOT rewrite, weaken, delete, or add acceptance criteria.",
    "- You MUST NOT change the verification plan gating steps or goal kind.",
    "- The plan contract (OBJECTIVE + acceptance criteria + verification plan) is FROZEN.",
    "- You may only recommend changes to implementation approach / task checklist / strategy.",
    "- Write a strategy note for the implementer, not a new plan.",
    "",
    "## Inputs",
    "",
    `OBJECTIVE: ${input.objective}`,
    "",
    "PLAN (read-only contract):",
    "```markdown",
    input.planMarkdown,
    "```",
    "",
    "RECENT GAPS:",
    gapList,
    "",
    "HISTORY NOTES:",
    history,
    "",
    "## Output",
    "",
    "Write a short strategy note (`strategy.md` body):",
    "1. Root cause in 1–3 sentences",
    "2. ONE structural HOW change (refactor, split, rewrite a subsystem, make behavior testable)",
    "3. Ordered mechanical steps the implementer can execute",
    "",
    "Do NOT emit a full plan. Do NOT modify acceptance criteria.",
  ].join("\n");
}