/**
 * Data access layer for Disciples.
 *
 * Provides queries for browsing disciples by letter, place, year, and search.
 * Uses the BFF API instead of direct Prisma queries.
 *
 * Disciples have an initiatedName and suffix (e.g., "Dasa", "Devi Dasi", "Sw").
 * The letter index aggregates disciples by the first letter of their initiatedName.
 * Place and year groupings allow browsing by initiation location and year.
 */

import { bff, bffList } from "@/lib/bff";

// Types

export type DiscipleSummary = {
  id: string;
  initiatedName: string;
  suffix: string;
  initiationDate: Date | null;
  initiationPlace: string | null;
  isVerified: boolean;
};

export type LetterCount = {
  letter: string;
  count: number;
};

export type PlaceGroup = {
  name: string;
  count: number;
};

export type YearGroup = {
  year: number;
  count: number;
};

// --- Suffix filter type ---

export type SuffixFilter = "all" | "Dasa" | "Devi Dasi";

// --- BFF response types (snake_case from Go API) ---

type BffDisciple = {
  id: string;
  initiated_name: string;
  suffix: string;
  initiation_date: string | null;
  initiation_place: string | null;
  karmi_name: string | null;
  is_verified: boolean;
};

type BffLetterCount = {
  _id: string;
  count: number;
};

type BffSuffixCount = {
  _id: string;
  count: number;
};

// --- Field mapping helper ---

function mapDisciple(d: BffDisciple): DiscipleSummary {
  return {
    id: d.id,
    initiatedName: d.initiated_name,
    suffix: d.suffix,
    initiationDate: d.initiation_date ? new Date(d.initiation_date) : null,
    initiationPlace: d.initiation_place ?? null,
    isVerified: d.is_verified,
  };
}

// --- Count ---

/** Get total number of disciples in the collection. */
export async function getTotalDiscipleCount(): Promise<number> {
  const result = await bff<{ total: number }>("/disciples/count");
  return result?.total ?? 0;
}

/** Get count of disciples matching optional letter + suffix filters. */
export async function getFilteredDiscipleCount(
  letter: string | null,
  suffix: SuffixFilter = "all",
): Promise<number> {
  const params: Record<string, string> = {};
  if (letter) params.letter = letter;
  if (suffix !== "all") params.suffix = suffix;

  // If no filters, just use total count endpoint
  if (!letter && suffix === "all") {
    return getTotalDiscipleCount();
  }

  // Fetch filtered list and count client-side
  // TODO: Consider adding a dedicated BFF count endpoint with filter params for better performance
  const disciples = await bffList<BffDisciple>("/disciples", { params });
  return disciples.length;
}

// --- Letter-based queries ---

/**
 * Get all disciples whose initiatedName starts with the given letter.
 *
 * Uses BFF endpoint with letter query param.
 * Results are ordered by initiatedName ascending (handled by BFF).
 */
export async function getDisciplesByLetter(
  letter: string,
): Promise<DiscipleSummary[]> {
  const disciples = await bffList<BffDisciple>("/disciples", {
    params: { letter },
  });
  return disciples.map(mapDisciple);
}

/**
 * Get all disciples, optionally filtered by suffix.
 *
 * Returns all 4,700+ disciples when no suffix filter is applied.
 * Ordered by initiatedName ascending.
 */
export async function getAllDisciples(
  suffix: SuffixFilter = "all",
): Promise<DiscipleSummary[]> {
  const params: Record<string, string> = {};
  if (suffix !== "all") params.suffix = suffix;

  const disciples = await bffList<BffDisciple>("/disciples", { params });
  return disciples.map(mapDisciple);
}

/**
 * Get disciples filtered by letter and/or suffix.
 *
 * Supports:
 *   - letter=null + suffix → all disciples with that suffix
 *   - letter + suffix="all" → all disciples starting with that letter
 *   - letter + suffix → disciples starting with that letter AND matching suffix
 *
 * Ordered by initiatedName ascending.
 */
export async function getFilteredDisciples(
  letter: string | null,
  suffix: SuffixFilter = "all",
): Promise<DiscipleSummary[]> {
  const params: Record<string, string> = {};
  if (letter) params.letter = letter;
  if (suffix !== "all") params.suffix = suffix;

  const disciples = await bffList<BffDisciple>("/disciples", { params });
  return disciples.map(mapDisciple);
}

/**
 * Get counts of disciples grouped by suffix.
 *
 * Returns { suffix: string, count: number }[] sorted by count desc.
 */
export async function getDiscipleSuffixCounts(): Promise<
  { suffix: string; count: number }[]
> {
  const suffixes = await bffList<BffSuffixCount>("/disciples/suffixes");
  return suffixes
    .map((s) => ({ suffix: s._id, count: s.count }))
    .sort((a, b) => b.count - a.count);
}

/**
 * Get counts of disciples grouped by the first letter of their initiatedName.
 *
 * Uses the BFF /disciples/letters endpoint which returns pre-aggregated data.
 * Returns results sorted alphabetically by letter.
 */
export async function getDiscipleLetterCounts(): Promise<LetterCount[]> {
  const letters = await bffList<BffLetterCount>("/disciples/letters");
  return letters
    .map((l) => ({ letter: l._id, count: l.count }))
    .sort((a, b) => a.letter.localeCompare(b.letter));
}

// --- Place-based queries ---

/**
 * Get unique initiation places with disciple counts.
 *
 * No dedicated BFF endpoint — fetches all disciples and aggregates in JS.
 * Returns results sorted by count descending.
 *
 * TODO: Add a BFF endpoint (GET /api/v1/disciples/places) for better performance.
 */
export async function getDisciplePlaces(): Promise<PlaceGroup[]> {
  const disciples = await bffList<BffDisciple>("/disciples");

  const counts: Record<string, number> = {};
  for (const d of disciples) {
    if (d.initiation_place) {
      counts[d.initiation_place] = (counts[d.initiation_place] || 0) + 1;
    }
  }

  return Object.entries(counts)
    .map(([name, count]) => ({ name, count }))
    .sort((a, b) => b.count - a.count);
}

/**
 * Get all disciples initiated at a given place.
 *
 * No dedicated BFF endpoint — fetches all disciples and filters in JS.
 * Results are ordered by initiatedName ascending.
 *
 * TODO: Add BFF query param support (GET /api/v1/disciples?place=...) for better performance.
 */
export async function getDisciplesByPlace(
  place: string,
): Promise<DiscipleSummary[]> {
  const disciples = await bffList<BffDisciple>("/disciples");

  return disciples
    .filter((d) => d.initiation_place === place)
    .map(mapDisciple)
    .sort((a, b) => a.initiatedName.localeCompare(b.initiatedName));
}

// --- Year-based queries ---

/**
 * Get unique initiation years with disciple counts.
 *
 * No dedicated BFF endpoint — fetches all disciples and aggregates years in JS.
 * Returns results sorted by year ascending.
 *
 * TODO: Add a BFF endpoint (GET /api/v1/disciples/years) for better performance.
 */
export async function getDiscipleYears(): Promise<YearGroup[]> {
  const disciples = await bffList<BffDisciple>("/disciples");

  const counts: Record<number, number> = {};
  for (const d of disciples) {
    if (d.initiation_date) {
      const year = new Date(d.initiation_date).getFullYear();
      if (!isNaN(year)) {
        counts[year] = (counts[year] || 0) + 1;
      }
    }
  }

  return Object.entries(counts)
    .map(([year, count]) => ({ year: Number(year), count }))
    .sort((a, b) => a.year - b.year);
}

/**
 * Get all disciples initiated in a given year.
 *
 * No dedicated BFF endpoint — fetches all disciples and filters in JS.
 * Results are ordered by initiatedName ascending.
 *
 * TODO: Add BFF query param support (GET /api/v1/disciples?year=...) for better performance.
 */
export async function getDisciplesByYear(
  year: number,
): Promise<DiscipleSummary[]> {
  const disciples = await bffList<BffDisciple>("/disciples");

  return disciples
    .filter((d) => {
      if (!d.initiation_date) return false;
      const dYear = new Date(d.initiation_date).getFullYear();
      return dYear === year;
    })
    .map(mapDisciple)
    .sort((a, b) => a.initiatedName.localeCompare(b.initiatedName));
}

// --- Search ---

/**
 * Search disciples by initiatedName using case-insensitive matching.
 *
 * Uses BFF search endpoint.
 * Results are limited to 100 and ordered by initiatedName ascending.
 */
export async function searchDisciples(
  query: string,
): Promise<DiscipleSummary[]> {
  const disciples = await bffList<BffDisciple>("/disciples/search", {
    params: { q: query },
  });
  return disciples.map(mapDisciple);
}