import { randomUUID } from "node:crypto";
import { Client } from "@microsoft/microsoft-graph-client";
import { PlanContext, Priority, Progress, RecentTaskContext } from "../llm/types";

/**
 * Thin wrapper around the Graph Planner endpoints we actually use.
 *
 * IMPORTANT: Planner write endpoints require the resource's @odata.etag in
 * an If-Match header. We always re-fetch immediately before PATCH/DELETE
 * to grab a fresh ETag.
 */
export class PlannerClient {
  constructor(private readonly graph: Client) {}

  /** All plans the signed-in user can see, with buckets/members/labels pre-fetched.
   *  Plans whose title contains "deprecated" (case-insensitive) are filtered out
   *  so old/archived plans don't pollute the LLM context.
   */
  async listPlansWithBuckets(): Promise<PlanContext[]> {
    const [plansResp, me] = await Promise.all([
      this.graph.api("/me/planner/plans").get(),
      this.graph.api("/me").select(["id"]).get(),
    ]);

    const meId: string = me.id;
    const plans: Array<{ id: string; title: string; owner?: string }> = (plansResp.value ?? [])
      .filter((p: { title?: string }) => !/deprecated/i.test(p.title ?? ""));

    const enriched = await Promise.all(
      plans.map(async (p) => {
        // Buckets + plan-details + group-members in parallel.
        const [bucketsResp, planDetails, groupMembers] = await Promise.all([
          this.graph.api(`/planner/plans/${p.id}/buckets`).get(),
          this.graph
            .api(`/planner/plans/${p.id}/details`)
            .get()
            .catch(() => ({ categoryDescriptions: {} })),
          this.fetchPlanMembers(p.id, p.owner),
        ]);

        const buckets: Array<{ id: string; name: string }> = bucketsResp.value ?? [];
        const cd = (planDetails.categoryDescriptions ?? {}) as Record<string, string | null>;
        const labels = Object.entries(cd)
          .map(([key, name]) => ({ key, name }))
          .filter((x): x is { key: string; name: string } => typeof x.name === "string" && x.name.length > 0)
          .map((x) => ({ slot: slotFromKey(x.key), name: x.name }))
          .filter((l) => l.slot > 0);

        return {
          planId: p.id,
          planTitle: p.title,
          buckets: buckets.map((b) => ({ bucketId: b.id, bucketTitle: b.name })),
          members: groupMembers.map((m) => ({
            userId: m.id,
            displayName: m.displayName,
            ...(m.id === meId ? { isMe: true as const } : {}),
          })),
          labels,
        } satisfies PlanContext;
      }),
    );

    return enriched;
  }

  /** Resolve owning M365 group's members. Falls back gracefully if owner missing. */
  private async fetchPlanMembers(
    planId: string,
    ownerGroupId?: string,
  ): Promise<Array<{ id: string; displayName: string }>> {
    let groupId = ownerGroupId;
    if (!groupId) {
      const plan = await this.graph
        .api(`/planner/plans/${planId}`)
        .select(["id", "owner"])
        .get()
        .catch(() => undefined);
      groupId = plan?.owner;
    }
    if (!groupId) return [];

    const resp = await this.graph
      .api(`/groups/${groupId}/members`)
      .select(["id", "displayName"])
      .get()
      .catch(() => ({ value: [] }));

    type DirObj = { id?: string; displayName?: string; "@odata.type"?: string };
    const users: Array<{ id: string; displayName: string }> = (resp.value ?? [])
      .filter((m: DirObj) => !m["@odata.type"] || m["@odata.type"] === "#microsoft.graph.user")
      .filter((m: DirObj): m is { id: string; displayName: string } =>
        typeof m.id === "string" && typeof m.displayName === "string" && m.displayName.length > 0,
      );
    return users;
  }

  /** Recent (non-completed) tasks across the user's plans, capped. */
  async listRecentTasks(limit = 20): Promise<RecentTaskContext[]> {
    const resp = await this.graph.api("/me/planner/tasks").get();
    type RawTask = {
      id: string;
      title: string;
      planId: string;
      bucketId: string;
      percentComplete: number;
      priority?: number;
      assignments?: Record<string, unknown>;
      createdDateTime: string;
    };
    const tasks: RawTask[] = resp.value ?? [];

    return tasks
      .filter((t) => t.percentComplete < 100)
      .sort((a, b) => (a.createdDateTime < b.createdDateTime ? 1 : -1))
      .slice(0, limit)
      .map<RecentTaskContext>((t) => ({
        taskId: t.id,
        title: t.title,
        planId: t.planId,
        bucketId: t.bucketId,
        percentComplete: t.percentComplete,
        priority: priorityFromInt(t.priority),
        assigneeIds: t.assignments ? Object.keys(t.assignments) : undefined,
      }));
  }

  async createTask(args: {
    planId: string;
    bucketId: string;
    title: string;
    progress?: Progress;
    priority?: Priority;
    startDate?: string;
    dueDate?: string;
    description?: string;
    assigneeUserIds?: string[];
    /** Plan-label slots (1..25) to apply. */
    categorySlots?: number[];
    checklistItems?: string[];
  }): Promise<{ taskId: string; checklistOverflow: number }> {
    const body: Record<string, unknown> = {
      planId: args.planId,
      bucketId: args.bucketId,
      title: args.title,
      percentComplete: progressToPercent(args.progress) ?? 0,
    };
    if (args.startDate) body.startDateTime = toIsoStartOfDay(args.startDate);
    if (args.dueDate) body.dueDateTime = toIsoEod(args.dueDate);
    const priorityInt = priorityToInt(args.priority);
    if (priorityInt !== undefined) body.priority = priorityInt;
    if (args.assigneeUserIds && args.assigneeUserIds.length) {
      body.assignments = buildAssignmentsForCreate(args.assigneeUserIds);
    }
    if (args.categorySlots && args.categorySlots.length) {
      body.appliedCategories = buildAppliedCategories(args.categorySlots);
    }

    const created = await this.graph.api("/planner/tasks").post(body);
    const taskId: string = created.id;

    // Combine description + checklist into a single details PATCH.
    const checklistItems = (args.checklistItems ?? []).slice(0, 20);
    const checklistOverflow = Math.max(0, (args.checklistItems?.length ?? 0) - 20);
    if (args.description || checklistItems.length > 0) {
      const detailsPatch: Record<string, unknown> = {};
      if (args.description) detailsPatch.description = args.description;
      if (checklistItems.length > 0) detailsPatch.checklist = buildChecklist(checklistItems);

      const details = await this.graph.api(`/planner/tasks/${taskId}/details`).get();
      const etag: string = details["@odata.etag"];
      await this.graph
        .api(`/planner/tasks/${taskId}/details`)
        .header("If-Match", etag)
        .header("Prefer", "return=representation")
        .patch(detailsPatch);
    }

    return { taskId, checklistOverflow };
  }

  async updateTask(args: {
    taskId: string;
    newBucketId?: string;
    progress?: Progress;
    percentComplete?: number;
    priority?: Priority;
    startDate?: string;
    dueDate?: string;
    newTitle?: string;
    /** When provided, this is the full new set of assignees — old ones are removed. */
    assigneeUserIds?: string[];
    currentAssigneeIds?: string[];
    /** Plan-label slots (1..25) to apply (full set after this update). */
    categorySlots?: number[];
    currentCategorySlots?: number[];
  }): Promise<void> {
    const current = await this.graph.api(`/planner/tasks/${args.taskId}`).get();
    const etag: string = current["@odata.etag"];

    const patch: Record<string, unknown> = {};
    const pct = args.percentComplete ?? progressToPercent(args.progress);
    if (pct !== undefined) patch.percentComplete = pct;
    if (args.newTitle) patch.title = args.newTitle;
    if (args.startDate) patch.startDateTime = toIsoStartOfDay(args.startDate);
    if (args.dueDate) patch.dueDateTime = toIsoEod(args.dueDate);
    if (args.newBucketId) patch.bucketId = args.newBucketId;
    const priorityInt = priorityToInt(args.priority);
    if (priorityInt !== undefined) patch.priority = priorityInt;

    if (args.assigneeUserIds) {
      patch.assignments = buildAssignmentsForReplace(
        args.currentAssigneeIds ?? [],
        args.assigneeUserIds,
      );
    }

    if (args.categorySlots) {
      patch.appliedCategories = buildAppliedCategoriesDiff(
        args.currentCategorySlots ?? [],
        args.categorySlots,
      );
    }

    if (Object.keys(patch).length === 0) return;

    await this.graph
      .api(`/planner/tasks/${args.taskId}`)
      .header("If-Match", etag)
      .patch(patch);
  }

  /** Append items to a task's existing checklist on its /details resource.
   *  Returns how many items overflowed (Planner caps at 20). */
  async appendChecklist(taskId: string, items: string[]): Promise<{ overflow: number }> {
    if (items.length === 0) return { overflow: 0 };
    const details = await this.graph.api(`/planner/tasks/${taskId}/details`).get();
    const etag: string = details["@odata.etag"];
    const existing = (details.checklist ?? {}) as Record<string, unknown>;
    const remainingCapacity = Math.max(0, 20 - Object.keys(existing).length);
    const toAdd = items.slice(0, remainingCapacity);
    const overflow = items.length - toAdd.length;
    if (toAdd.length === 0) return { overflow };

    const additions = buildChecklist(toAdd);
    await this.graph
      .api(`/planner/tasks/${taskId}/details`)
      .header("If-Match", etag)
      .patch({ checklist: additions });
    return { overflow };
  }

  async appendTaskNote(taskId: string, note: string): Promise<void> {
    const details = await this.graph.api(`/planner/tasks/${taskId}/details`).get();
    const etag: string = details["@odata.etag"];
    const previous: string = details.description ?? "";
    const stamp = new Date().toISOString().slice(0, 16).replace("T", " ");
    const combined = previous
      ? `${previous}\n[${stamp}] ${note}`
      : `[${stamp}] ${note}`;
    await this.graph
      .api(`/planner/tasks/${taskId}/details`)
      .header("If-Match", etag)
      .patch({ description: combined });
  }

  /** Ensure a plan-level label exists with the given name. Returns its slot
   *  (1..25). Picks the lowest empty slot for new labels. Throws if 25 slots
   *  are all taken. */
  async ensurePlanLabel(planId: string, name: string): Promise<number> {
    const details = await this.graph.api(`/planner/plans/${planId}/details`).get();
    const etag: string = details["@odata.etag"];
    const cd = (details.categoryDescriptions ?? {}) as Record<string, string | null>;

    for (let slot = 1; slot <= 25; slot++) {
      const key = `category${slot}`;
      if (cd[key] && cd[key].trim().toLowerCase() === name.trim().toLowerCase()) {
        return slot;
      }
    }
    let emptySlot: number | null = null;
    for (let slot = 1; slot <= 25; slot++) {
      const key = `category${slot}`;
      if (!cd[key]) {
        emptySlot = slot;
        break;
      }
    }
    if (emptySlot === null) {
      throw new Error(`Plan 의 라벨 슬롯이 25개 모두 차있어 '${name}' 을 등록할 수 없어요.`);
    }
    await this.graph
      .api(`/planner/plans/${planId}/details`)
      .header("If-Match", etag)
      .patch({ categoryDescriptions: { [`category${emptySlot}`]: name } });
    return emptySlot;
  }
}

function progressToPercent(p?: Progress): number | undefined {
  switch (p) {
    case "notStarted":
      return 0;
    case "inProgress":
      return 50;
    case "completed":
      return 100;
    default:
      return undefined;
  }
}

function priorityToInt(p?: Priority): number | undefined {
  switch (p) {
    case "urgent":
      return 1;
    case "important":
      return 3;
    case "medium":
      return 5;
    case "low":
      return 9;
    default:
      return undefined;
  }
}

function priorityFromInt(n?: number): Priority | undefined {
  if (n === undefined) return undefined;
  if (n <= 1) return "urgent";
  if (n <= 3) return "important";
  if (n <= 5) return "medium";
  return "low";
}

function buildAssignmentsForCreate(userIds: string[]): Record<string, unknown> {
  const out: Record<string, unknown> = {};
  for (const id of userIds) {
    out[id] = {
      "@odata.type": "#microsoft.graph.plannerAssignment",
      orderHint: " !",
    };
  }
  return out;
}

/** Build an assignments PATCH that removes old assignees (set to null) and
 *  adds the new ones, preserving any user who is in both sets. */
function buildAssignmentsForReplace(
  currentIds: string[],
  newIds: string[],
): Record<string, unknown> {
  const out: Record<string, unknown> = {};
  const current = new Set(currentIds);
  const target = new Set(newIds);
  for (const id of current) {
    if (!target.has(id)) out[id] = null;
  }
  for (const id of target) {
    if (!current.has(id)) {
      out[id] = {
        "@odata.type": "#microsoft.graph.plannerAssignment",
        orderHint: " !",
      };
    }
  }
  return out;
}

function buildAppliedCategories(slots: number[]): Record<string, boolean> {
  const out: Record<string, boolean> = {};
  for (const s of slots) {
    if (s >= 1 && s <= 25) out[`category${s}`] = true;
  }
  return out;
}

/** Diff appliedCategories so we explicitly set removed slots to false. */
function buildAppliedCategoriesDiff(
  currentSlots: number[],
  newSlots: number[],
): Record<string, boolean> {
  const out: Record<string, boolean> = {};
  const target = new Set(newSlots);
  for (const s of currentSlots) {
    if (!target.has(s)) out[`category${s}`] = false;
  }
  for (const s of newSlots) {
    if (s >= 1 && s <= 25) out[`category${s}`] = true;
  }
  return out;
}

function buildChecklist(items: string[]): Record<string, unknown> {
  const out: Record<string, unknown> = {};
  for (const title of items) {
    out[randomUUID()] = {
      "@odata.type": "#microsoft.graph.plannerChecklistItem",
      title,
      isChecked: false,
    };
  }
  return out;
}

function slotFromKey(key: string): number {
  const m = /^category(\d+)$/.exec(key);
  return m ? Number(m[1]) : 0;
}

function toIsoEod(yyyyMmDd: string): string {
  return `${yyyyMmDd}T23:59:59Z`;
}

function toIsoStartOfDay(yyyyMmDd: string): string {
  return `${yyyyMmDd}T00:00:00Z`;
}