import type { ConvoyStatus, ConvoyTransitionErrorCode } from "./schemas";

export const VALID_TRANSITIONS: Record<ConvoyStatus, ConvoyStatus[]> = {
  draft: ["convoy_review", "blocked", "cancelled"],
  convoy_review: ["ready", "draft", "blocked", "cancelled"],
  ready: ["in_progress", "blocked", "cancelled"],
  in_progress: ["pr_review", "blocked", "cancelled"],
  pr_review: ["merged", "in_progress", "blocked", "cancelled"],
  merged: ["released", "blocked"],
  released: [],
  blocked: [
    "draft",
    "convoy_review",
    "ready",
    "in_progress",
    "pr_review",
    "merged",
    "cancelled",
  ],
  cancelled: [],
};

type TransitionRule = {
  from: ConvoyStatus;
  to: ConvoyStatus;
  actors: readonly string[];
  requiresReason?: boolean;
};

/** Explicit (from, to, actor) allow-list — gate actors are never implied by pipeline roles. */
export const ALLOWED_TRANSITIONS: readonly TransitionRule[] = [
  { from: "draft", to: "convoy_review", actors: ["role-architect"] },
  {
    from: "draft",
    to: "blocked",
    actors: ["role-architect", "role-conductor", "human-gate-1", "automation"],
    requiresReason: true,
  },
  {
    from: "draft",
    to: "cancelled",
    actors: ["human-gate-1", "role-conductor"],
    requiresReason: true,
  },
  { from: "convoy_review", to: "ready", actors: ["human-gate-1"] },
  { from: "convoy_review", to: "draft", actors: ["human-gate-1"] },
  {
    from: "convoy_review",
    to: "blocked",
    actors: ["human-gate-1", "role-architect", "automation"],
    requiresReason: true,
  },
  {
    from: "convoy_review",
    to: "cancelled",
    actors: ["human-gate-1"],
    requiresReason: true,
  },
  { from: "ready", to: "in_progress", actors: ["role-implementer"] },
  {
    from: "ready",
    to: "blocked",
    actors: ["role-implementer", "human-gate-1", "automation"],
    requiresReason: true,
  },
  {
    from: "ready",
    to: "cancelled",
    actors: ["human-gate-1", "role-conductor"],
    requiresReason: true,
  },
  { from: "in_progress", to: "pr_review", actors: ["role-implementer", "automation"] },
  {
    from: "in_progress",
    to: "blocked",
    actors: ["role-implementer", "human-gate-2", "automation"],
    requiresReason: true,
  },
  {
    from: "in_progress",
    to: "cancelled",
    actors: ["human-gate-1", "role-conductor"],
    requiresReason: true,
  },
  { from: "pr_review", to: "merged", actors: ["human-gate-2"] },
  { from: "pr_review", to: "in_progress", actors: ["human-gate-2", "role-implementer"] },
  {
    from: "pr_review",
    to: "blocked",
    actors: ["human-gate-2", "automation"],
    requiresReason: true,
  },
  {
    from: "pr_review",
    to: "cancelled",
    actors: ["human-gate-1", "human-gate-2"],
    requiresReason: true,
  },
  { from: "merged", to: "released", actors: ["human-gate-3"] },
  {
    from: "merged",
    to: "blocked",
    actors: ["human-gate-3", "automation"],
    requiresReason: true,
  },
  {
    from: "blocked",
    to: "draft",
    actors: ["human-gate-1", "role-conductor", "automation"],
    requiresReason: true,
  },
  {
    from: "blocked",
    to: "convoy_review",
    actors: ["human-gate-1", "role-conductor", "automation"],
    requiresReason: true,
  },
  {
    from: "blocked",
    to: "ready",
    actors: ["human-gate-1", "role-conductor", "automation"],
    requiresReason: true,
  },
  {
    from: "blocked",
    to: "in_progress",
    actors: ["human-gate-2", "role-conductor", "automation"],
    requiresReason: true,
  },
  {
    from: "blocked",
    to: "pr_review",
    actors: ["human-gate-2", "role-conductor", "automation"],
    requiresReason: true,
  },
  {
    from: "blocked",
    to: "merged",
    actors: ["human-gate-2", "role-conductor", "automation"],
    requiresReason: true,
  },
  {
    from: "blocked",
    to: "cancelled",
    actors: ["human-gate-1", "human-gate-2", "human-gate-3", "role-conductor"],
    requiresReason: true,
  },
];

export class ConvoyTransitionError extends Error {
  readonly code: ConvoyTransitionErrorCode;

  constructor(message: string, code: ConvoyTransitionErrorCode) {
    super(message);
    this.name = "ConvoyTransitionError";
    this.code = code;
  }
}

export function validateConvoyTransition(input: {
  from: ConvoyStatus;
  to: ConvoyStatus;
  actor: string;
  reason?: string;
}): void {
  const allowedTargets = VALID_TRANSITIONS[input.from];
  if (!allowedTargets.includes(input.to)) {
    throw new ConvoyTransitionError(
      `Invalid transition ${input.from} → ${input.to}`,
      "INVALID_TRANSITION",
    );
  }

  const rule = ALLOWED_TRANSITIONS.find(
    (candidate) => candidate.from === input.from && candidate.to === input.to,
  );

  if (!rule) {
    throw new ConvoyTransitionError(
      `No actor may perform transition ${input.from} → ${input.to}`,
      "FORBIDDEN_ACTOR",
    );
  }

  if (!rule.actors.includes(input.actor)) {
    throw new ConvoyTransitionError(
      `Actor ${input.actor} cannot perform transition ${input.from} → ${input.to}`,
      "FORBIDDEN_ACTOR",
    );
  }

  if (rule.requiresReason && !input.reason?.trim()) {
    throw new ConvoyTransitionError(
      `Transition ${input.from} → ${input.to} requires a reason`,
      "REASON_REQUIRED",
    );
  }
}

/** Map local `.convoys/*.md` frontmatter status to server enum for reconcile. */
export const FILE_STATUS_TO_SERVER: Record<string, ConvoyStatus> = {
  open: "draft",
  "in-progress": "in_progress",
  merged: "merged",
  shipped: "released",
  abandoned: "cancelled",
};

export function mapFileStatusToServer(fileStatus: string): ConvoyStatus | null {
  return FILE_STATUS_TO_SERVER[fileStatus] ?? null;
}