import type {
  MessageBlock,
  PlanBlock,
  PlanStatus,
  PlanStep,
  PlanStepStatus,
} from "@rakazo/contracts";
import { PLAN_LIMITS, PlanBlockSchema, PlanStepStatusSchema } from "@rakazo/contracts";

function clip(value: string, max: number): string {
  const flat = value.replace(/\s+/g, " ").trim();
  return flat.length > max ? `${flat.slice(0, max - 1).trimEnd()}…` : flat;
}

export interface PlanCreateArgs {
  title?: unknown;
  steps?: unknown;
  await_approval?: unknown;
}

export interface PlanUpdateArgs {
  plan_id?: unknown;
  steps?: unknown;
}

function derivePlanStatus(steps: readonly PlanStep[], awaitingApproval = false): PlanStatus {
  if (steps.length > 0 && steps.every((s) => s.status === "completed" || s.status === "skipped")) {
    return "completed";
  }
  if (awaitingApproval && steps.every((s) => s.status === "pending")) {
    return "awaiting_approval";
  }
  return "active";
}

/** Build a validated PlanBlock from `plan_create` tool arguments. */
export function buildPlanFromTool(
  args: PlanCreateArgs,
  planId: string,
): { ok: true; block: PlanBlock; awaitApproval: boolean } | { error: string } {
  const rawTitle = typeof args.title === "string" ? clip(args.title, PLAN_LIMITS.title) : "";
  if (!rawTitle) return { error: "title is required." };
  const rawSteps = Array.isArray(args.steps) ? args.steps : [];
  const steps: PlanStep[] = [];
  for (const item of rawSteps) {
    const label =
      typeof item === "string"
        ? clip(item, PLAN_LIMITS.stepLabel)
        : item &&
            typeof item === "object" &&
            typeof (item as { label?: unknown }).label === "string"
          ? clip((item as { label: string }).label, PLAN_LIMITS.stepLabel)
          : "";
    if (!label) continue;
    const rawStatus =
      item && typeof item === "object" ? (item as { status?: unknown }).status : undefined;
    const parsedStatus = PlanStepStatusSchema.safeParse(rawStatus);
    const note =
      item && typeof item === "object" && typeof (item as { note?: unknown }).note === "string"
        ? clip((item as { note: string }).note, PLAN_LIMITS.stepNote)
        : undefined;
    steps.push({
      id: `s${steps.length + 1}`,
      label,
      status: parsedStatus.success ? parsedStatus.data : "pending",
      ...(note ? { note } : {}),
    });
    if (steps.length >= PLAN_LIMITS.maxSteps) break;
  }
  if (steps.length < PLAN_LIMITS.minSteps) {
    return {
      error: `steps must contain at least ${PLAN_LIMITS.minSteps} non-empty steps.`,
    };
  }
  const awaitApproval = args.await_approval === true;
  if (!awaitApproval && steps.every((s) => s.status === "pending")) {
    steps[0] = { ...steps[0]!, status: "in_progress" };
  }
  const status = derivePlanStatus(steps, awaitApproval);
  const parsed = PlanBlockSchema.safeParse({
    kind: "plan",
    planId,
    title: rawTitle,
    status,
    steps,
  });
  if (!parsed.success) {
    const issue = parsed.error.issues[0];
    return { error: `Plan is not valid: ${issue?.path.join(".")} ${issue?.message}`.trim() };
  }
  return { ok: true, block: parsed.data, awaitApproval };
}

export interface PlanStepUpdateInput {
  id?: string;
  index?: number;
  status: PlanStepStatus;
  label?: string;
  note?: string;
}

export function parsePlanStepUpdates(
  rawUpdates: unknown,
): { ok: true; updates: PlanStepUpdateInput[] } | { error: string } {
  if (!Array.isArray(rawUpdates) || rawUpdates.length === 0) {
    return { error: "steps must be a non-empty array of step updates." };
  }
  const updates: PlanStepUpdateInput[] = [];
  for (const raw of rawUpdates) {
    if (!raw || typeof raw !== "object") continue;
    const item = raw as Record<string, unknown>;
    const parsedStatus = PlanStepStatusSchema.safeParse(item.status);
    if (!parsedStatus.success) {
      return {
        error: "Each step update requires status: pending, in_progress, completed, or skipped.",
      };
    }
    const id = typeof item.id === "string" && item.id.trim() ? item.id.trim() : undefined;
    const index =
      typeof item.index === "number" && Number.isInteger(item.index) && item.index >= 1
        ? item.index
        : undefined;
    if (!id && index === undefined) {
      return { error: "Each step update requires id (e.g. 's1') or 1-based index." };
    }
    const label =
      typeof item.label === "string" && item.label.trim()
        ? clip(item.label, PLAN_LIMITS.stepLabel)
        : undefined;
    const note = typeof item.note === "string" ? clip(item.note, PLAN_LIMITS.stepNote) : undefined;
    updates.push({
      ...(id ? { id } : {}),
      ...(index !== undefined ? { index } : {}),
      status: parsedStatus.data,
      ...(label ? { label } : {}),
      ...(note !== undefined ? { note } : {}),
    });
  }
  if (updates.length === 0) {
    return { error: "Provide at least one valid step update." };
  }
  return { ok: true, updates };
}

/** Apply step updates to an existing PlanBlock; returns null if nothing matched or changed. */
export function applyPlanStepUpdates(
  plan: PlanBlock,
  updates: readonly PlanStepUpdateInput[],
): PlanBlock | null {
  let changed = false;
  const nextSteps = plan.steps.map((step, idx) => {
    const match = updates.find(
      (u) => (u.id && u.id === step.id) || (u.index !== undefined && u.index === idx + 1),
    );
    if (!match) return step;
    const nextLabel = match.label ?? step.label;
    const nextNote = match.note !== undefined ? match.note || undefined : step.note;
    if (
      step.status === match.status &&
      step.label === nextLabel &&
      (step.note ?? undefined) === nextNote
    ) {
      return step;
    }
    changed = true;
    return {
      id: step.id,
      label: nextLabel,
      status: match.status,
      ...(nextNote ? { note: nextNote } : {}),
    };
  });
  const nextStatus = derivePlanStatus(nextSteps, false);
  if (!changed && plan.status === nextStatus) return null;
  return {
    ...plan,
    status: nextStatus,
    steps: nextSteps,
  };
}

/** Update a matching plan block inside a message's blocks array. */
export function updatePlanInBlocks(
  blocks: readonly MessageBlock[],
  planId: string | undefined,
  updates: readonly PlanStepUpdateInput[],
): { blocks: MessageBlock[]; plan: PlanBlock } | null {
  let updatedPlan: PlanBlock | null = null;
  const next = blocks.map((block) => {
    if (block.kind !== "plan") return block;
    if (planId && block.planId !== planId) return block;
    if (updatedPlan) return block;
    const applied = applyPlanStepUpdates(block, updates);
    if (!applied) return block;
    updatedPlan = applied;
    return applied;
  });
  return updatedPlan ? { blocks: next, plan: updatedPlan } : null;
}

const STEP_GLYPH: Record<PlanStepStatus, string> = {
  completed: "✓",
  in_progress: "▸",
  pending: "○",
  skipped: "–",
};

/** How a later turn reads a plan block in conversation history. */
export function planHistoryText(block: PlanBlock): string {
  const done = block.steps.filter((s) => s.status === "completed").length;
  const lines = block.steps.map(
    (s, idx) =>
      `  ${idx + 1}. [${STEP_GLYPH[s.status]} ${s.status}] ${s.label}${s.note ? ` — ${s.note}` : ""} (${s.id})`,
  );
  return `[plan ${block.planId} (${block.status}, ${done}/${block.steps.length} done): ${block.title}]\n${lines.join("\n")}`;
}