import { eq, inArray } from "drizzle-orm";
import type { Db } from "@paperclip/db";
import { projects, projectGoals, goals } from "@paperclip/db";
import type { ProjectGoalRef } from "@paperclip/shared";

type ProjectRow = typeof projects.$inferSelect;

interface ProjectWithGoals extends ProjectRow {
  goalIds: string[];
  goals: ProjectGoalRef[];
}

/** Batch-load goal refs for a set of projects. */
async function attachGoals(db: Db, rows: ProjectRow[]): Promise<ProjectWithGoals[]> {
  if (rows.length === 0) return [];

  const projectIds = rows.map((r) => r.id);

  // Fetch join rows + goal titles in one query
  const links = await db
    .select({
      projectId: projectGoals.projectId,
      goalId: projectGoals.goalId,
      goalTitle: goals.title,
    })
    .from(projectGoals)
    .innerJoin(goals, eq(projectGoals.goalId, goals.id))
    .where(inArray(projectGoals.projectId, projectIds));

  const map = new Map<string, ProjectGoalRef[]>();
  for (const link of links) {
    let arr = map.get(link.projectId);
    if (!arr) {
      arr = [];
      map.set(link.projectId, arr);
    }
    arr.push({ id: link.goalId, title: link.goalTitle });
  }

  return rows.map((r) => {
    const g = map.get(r.id) ?? [];
    return { ...r, goalIds: g.map((x) => x.id), goals: g };
  });
}

/** Sync the project_goals join table for a single project. */
async function syncGoalLinks(db: Db, projectId: string, companyId: string, goalIds: string[]) {
  // Delete existing links
  await db.delete(projectGoals).where(eq(projectGoals.projectId, projectId));

  // Insert new links
  if (goalIds.length > 0) {
    await db.insert(projectGoals).values(
      goalIds.map((goalId) => ({ projectId, goalId, companyId })),
    );
  }
}

/** Resolve goalIds from input, handling the legacy goalId field. */
function resolveGoalIds(data: { goalIds?: string[]; goalId?: string | null }): string[] | undefined {
  if (data.goalIds !== undefined) return data.goalIds;
  if (data.goalId !== undefined) {
    return data.goalId ? [data.goalId] : [];
  }
  return undefined;
}

export function projectService(db: Db) {
  return {
    list: async (companyId: string): Promise<ProjectWithGoals[]> => {
      const rows = await db.select().from(projects).where(eq(projects.companyId, companyId));
      return attachGoals(db, rows);
    },

    getById: async (id: string): Promise<ProjectWithGoals | null> => {
      const row = await db
        .select()
        .from(projects)
        .where(eq(projects.id, id))
        .then((rows) => rows[0] ?? null);
      if (!row) return null;
      const [enriched] = await attachGoals(db, [row]);
      return enriched;
    },

    create: async (
      companyId: string,
      data: Omit<typeof projects.$inferInsert, "companyId"> & { goalIds?: string[] },
    ): Promise<ProjectWithGoals> => {
      const { goalIds: inputGoalIds, ...projectData } = data;
      const ids = resolveGoalIds({ goalIds: inputGoalIds, goalId: projectData.goalId });

      // Also write goalId to the legacy column (first goal or null)
      const legacyGoalId = ids && ids.length > 0 ? ids[0] : projectData.goalId ?? null;

      const row = await db
        .insert(projects)
        .values({ ...projectData, goalId: legacyGoalId, companyId })
        .returning()
        .then((rows) => rows[0]);

      if (ids && ids.length > 0) {
        await syncGoalLinks(db, row.id, companyId, ids);
      }

      const [enriched] = await attachGoals(db, [row]);
      return enriched;
    },

    update: async (
      id: string,
      data: Partial<typeof projects.$inferInsert> & { goalIds?: string[] },
    ): Promise<ProjectWithGoals | null> => {
      const { goalIds: inputGoalIds, ...projectData } = data;
      const ids = resolveGoalIds({ goalIds: inputGoalIds, goalId: projectData.goalId });

      // Keep legacy goalId column in sync
      const updates: Partial<typeof projects.$inferInsert> = {
        ...projectData,
        updatedAt: new Date(),
      };
      if (ids !== undefined) {
        updates.goalId = ids.length > 0 ? ids[0] : null;
      }

      const row = await db
        .update(projects)
        .set(updates)
        .where(eq(projects.id, id))
        .returning()
        .then((rows) => rows[0] ?? null);
      if (!row) return null;

      if (ids !== undefined) {
        await syncGoalLinks(db, id, row.companyId, ids);
      }

      const [enriched] = await attachGoals(db, [row]);
      return enriched;
    },

    remove: (id: string) =>
      db
        .delete(projects)
        .where(eq(projects.id, id))
        .returning()
        .then((rows) => rows[0] ?? null),
  };
}