import type { JobsheetSection, Page } from "../types/session";

export type FlatPage = {
  sectionId: string;
  sectionIndex: number;
  sectionTitle?: string;
  pageIndex: number;
  page: Page;
  flatIndex: number;
};

const MAX_PHOTOS_PRIMARY_PAGE = 2;
const MAX_PHOTOS_CONTINUATION_PAGE = 6;

function cloneTemplate(template?: Page["template"]): Page["template"] {
  if (!template) return undefined;
  return { ...template };
}

function normalizePhotoIds(photoIds?: string[]): string[] {
  if (!Array.isArray(photoIds)) return [];
  return photoIds.filter((value) => Boolean(value));
}

function buildPhotoContinuation(source: Page, photoIds: string[]): Page {
  return {
    items: [],
    template: cloneTemplate(source.template),
    photo_ids: photoIds,
    photo_layout: source.photo_layout,
    photo_order_locked: source.photo_order_locked,
    variant: "photos",
  };
}

function splitPagePhotos(page: Page): Page[] {
  const items = Array.isArray(page.items) ? page.items : [];
  const normalized: Page = { ...page, items };

  if (normalized.blank) {
    return [normalized];
  }

  const photoIds = normalizePhotoIds(normalized.photo_ids);
  if (!photoIds.length) {
    return [normalized];
  }

  if (normalized.variant === "photos") {
    const chunks: string[][] = [];
    for (let i = 0; i < photoIds.length; i += MAX_PHOTOS_CONTINUATION_PAGE) {
      chunks.push(photoIds.slice(i, i + MAX_PHOTOS_CONTINUATION_PAGE));
    }
    if (chunks.length <= 1) {
      return [
        {
          ...normalized,
          photo_ids: chunks[0] ?? [],
          variant: "photos",
        },
      ];
    }
    return chunks.map((chunk, idx) => {
      if (idx === 0) return { ...normalized, photo_ids: chunk, variant: "photos" };
      return buildPhotoContinuation(normalized, chunk);
    });
  }

  const baseChunk = photoIds.slice(0, MAX_PHOTOS_PRIMARY_PAGE);
  const extraIds = photoIds.slice(MAX_PHOTOS_PRIMARY_PAGE);
  const continuationChunks: string[][] = [];
  for (let i = 0; i < extraIds.length; i += MAX_PHOTOS_CONTINUATION_PAGE) {
    continuationChunks.push(extraIds.slice(i, i + MAX_PHOTOS_CONTINUATION_PAGE));
  }

  const basePage: Page = {
    ...normalized,
    photo_ids: baseChunk,
    variant: normalized.variant ?? "full",
  };
  if (!continuationChunks.length) {
    return [basePage];
  }
  const extraPages = continuationChunks.map((chunk) =>
    buildPhotoContinuation(normalized, chunk),
  );
  return [basePage, ...extraPages];
}

export function ensureSections(sections?: JobsheetSection[]): JobsheetSection[] {
  if (sections && sections.length) {
    return sections.map((section, index) => {
      const basePages = section.pages?.length ? section.pages : [{ items: [] }];
      const normalizedPages = basePages.flatMap((page) => splitPagePhotos(page));
      return {
        id: section.id,
        title: section.title ?? "Section",
        pages: normalizedPages.length ? normalizedPages : [{ items: [] }],
      };
    });
  }
  return [
    {
      id: crypto.randomUUID(),
      title: "Section 1",
      pages: [{ items: [] }],
    },
  ];
}

export function flattenSections(sections: JobsheetSection[]): FlatPage[] {
  const result: FlatPage[] = [];
  sections.forEach((section, sectionIndex) => {
    const pages = section.pages ?? [];
    pages.forEach((page, pageIndex) => {
      result.push({
        sectionId: section.id,
        sectionIndex,
        sectionTitle: section.title ?? `Section ${sectionIndex + 1}`,
        pageIndex,
        page,
        flatIndex: result.length,
      });
    });
  });
  return result;
}

export function replacePage(
  sections: JobsheetSection[],
  sectionIndex: number,
  pageIndex: number,
  nextPage: Page,
): JobsheetSection[] {
  const next = sections.map((section, sIdx) => {
    if (sIdx !== sectionIndex) return section;
    const nextPages = [...(section.pages ?? [])];
    nextPages[pageIndex] = nextPage;
    return { ...section, pages: nextPages };
  });
  return ensureSections(next);
}

export function insertPage(
  sections: JobsheetSection[],
  sectionIndex: number,
  pageIndex: number,
  page: Page,
): JobsheetSection[] {
  const next = sections.map((section, sIdx) => {
    if (sIdx !== sectionIndex) return section;
    const nextPages = [...(section.pages ?? [])];
    const safeIndex = Math.max(0, Math.min(pageIndex, nextPages.length));
    nextPages.splice(safeIndex, 0, page);
    return { ...section, pages: nextPages };
  });
  return ensureSections(next);
}

export function removePage(
  sections: JobsheetSection[],
  sectionIndex: number,
  pageIndex: number,
): JobsheetSection[] {
  const next = sections.map((section, sIdx) => {
    if (sIdx !== sectionIndex) return section;
    const nextPages = [...(section.pages ?? [])];
    if (nextPages.length <= 1) return section;
    nextPages.splice(pageIndex, 1);
    return { ...section, pages: nextPages.length ? nextPages : [{ items: [] }] };
  });
  return ensureSections(next);
}