import {
  BadRequestException,
  ForbiddenException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { ContentStatus, MediaEntityType, TechnicalFieldType } from '@prisma/client';
import { AuthUser } from '../auth/auth.types';
import { PermissionsService } from '../auth/permissions.service';
import { CategoryTechnicalFormService } from '../categories/category-technical-form.service';
import { PrismaService } from '../prisma/prisma.service';
import { ReplaceProductTechnicalInfoDto } from './dto/product-technical-info.dto';
import {
  decodeMultiValueText,
  encodeMultiValueText,
} from '../common/technical-multi-value.util';

type FormField = {
  id: string;
  label: string;
  key: string;
  type: TechnicalFieldType;
  isRequired: boolean;
  sortOrder: number;
  options: { id: string; label: string; value: string; sortOrder: number }[];
};

@Injectable()
export class ProductTechnicalInfoService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly permissions: PermissionsService,
    private readonly technicalFormService: CategoryTechnicalFormService,
  ) {}

  async getForProduct(
    businessIdRaw: string,
    productIdRaw: string,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const productId = BigInt(productIdRaw);
    await this.assertPermission(businessId, actor.id, 'products.read');

    return this.buildTechnicalInfoForProduct(businessId, productId);
  }

  async getPublicForProduct(businessIdRaw: string, productIdRaw: string) {
    const businessId = BigInt(businessIdRaw);
    const productId = BigInt(productIdRaw);

    await this.assertPublishedProductExists(businessId, productId);

    return this.buildTechnicalInfoForProduct(businessId, productId);
  }

  private async buildTechnicalInfoForProduct(
    businessId: bigint,
    productId: bigint,
  ) {
    const { product, categoryId } = await this.getProductWithCategory(
      businessId,
      productId,
    );

    if (!categoryId) {
      return {
        form: null,
        values: [],
        message: 'Product has no category assigned',
      };
    }

    const form = await this.technicalFormService.getFormForCategory(
      businessId,
      categoryId,
    );

    if (!form) {
      return { form: null, values: [] };
    }

    const values = await this.loadProductValues(
      businessId,
      product.id,
      form.fields,
    );

    return { form, values };
  }

  async replaceForProduct(
    businessIdRaw: string,
    productIdRaw: string,
    dto: ReplaceProductTechnicalInfoDto,
    actor: AuthUser,
  ) {
    const businessId = BigInt(businessIdRaw);
    const productId = BigInt(productIdRaw);
    await this.assertPermission(businessId, actor.id, 'products.update');

    const { product, categoryId } = await this.getProductWithCategory(
      businessId,
      productId,
    );

    if (!categoryId) {
      throw new BadRequestException(
        'Product must be assigned to a category before filling technical info',
      );
    }

    const form = await this.technicalFormService.getFormForCategory(
      businessId,
      categoryId,
    );

    if (!form) {
      throw new BadRequestException(
        'No technical form is defined for this product category',
      );
    }

    const fieldMap = new Map(form.fields.map((field) => [field.key, field]));
    const submittedKeys = new Set<string>();

    for (const entry of dto.values) {
      if (submittedKeys.has(entry.fieldKey)) {
        throw new BadRequestException(
          `Duplicate value for field "${entry.fieldKey}"`,
        );
      }
      submittedKeys.add(entry.fieldKey);

      const field = fieldMap.get(entry.fieldKey);
      if (!field) {
        throw new BadRequestException(
          `Unknown field key "${entry.fieldKey}"`,
        );
      }

      this.validateFieldValue(field, entry.value);
    }

    for (const field of form.fields) {
      if (field.isRequired && !submittedKeys.has(field.key)) {
        throw new BadRequestException(
          `Required field "${field.label}" is missing`,
        );
      }
    }

    await this.prisma.$transaction(async (tx) => {
      await tx.productTechnicalFieldValue.deleteMany({
        where: { businessId, productId: product.id },
      });

      for (const entry of dto.values) {
        const field = fieldMap.get(entry.fieldKey)!;
        const fieldId = BigInt(field.id);

        if (entry.value === null || entry.value === undefined || entry.value === '') {
          continue;
        }

        if (field.type === 'multi_value') {
          const items = Array.isArray(entry.value)
            ? entry.value.map((item) => String(item).trim()).filter(Boolean)
            : [];
          if (!items.length) continue;
          await tx.productTechnicalFieldValue.create({
            data: {
              businessId,
              productId: product.id,
              fieldId,
              textValue: encodeMultiValueText(items),
            },
          });
          continue;
        }

        if (field.type === 'text' || field.type === 'textarea') {
          await tx.productTechnicalFieldValue.create({
            data: {
              businessId,
              productId: product.id,
              fieldId,
              textValue: String(entry.value),
            },
          });
          continue;
        }

        if (field.type === 'select') {
          const option = this.findOptionByValue(field, entry.value as string);
          await tx.productTechnicalFieldValue.create({
            data: {
              businessId,
              productId: product.id,
              fieldId,
              optionId: BigInt(option.id),
            },
          });
          continue;
        }

        const selectedValues = entry.value as string[];
        if (!Array.isArray(selectedValues) || !selectedValues.length) {
          continue;
        }
        const fieldValue = await tx.productTechnicalFieldValue.create({
          data: {
            businessId,
            productId: product.id,
            fieldId,
          },
        });

        for (const rawValue of selectedValues) {
          const option = this.findOptionByValue(field, rawValue);
          await tx.productTechnicalFieldValueOption.create({
            data: {
              fieldValueId: fieldValue.id,
              optionId: BigInt(option.id),
            },
          });
        }
      }
    });

    return this.getForProduct(businessIdRaw, productIdRaw, actor);
  }

  private validateFieldValue(
    field: FormField,
    value: string | string[] | null | undefined,
  ) {
    if (value === null || value === undefined || value === '') {
      if (field.isRequired) {
        throw new BadRequestException(
          `Required field "${field.label}" cannot be empty`,
        );
      }
      return;
    }

    if (field.type === 'text' || field.type === 'textarea') {
      if (typeof value !== 'string') {
        throw new BadRequestException(
          `Field "${field.label}" expects a text value`,
        );
      }
      return;
    }

    if (field.type === 'multi_value') {
      if (!Array.isArray(value)) {
        throw new BadRequestException(
          `Field "${field.label}" expects an array of text values`,
        );
      }
      const items = value.map((item) => String(item).trim()).filter(Boolean);
      if (!items.length) {
        if (field.isRequired) {
          throw new BadRequestException(
            `Required field "${field.label}" cannot be empty`,
          );
        }
        return;
      }
      return;
    }

    if (field.type === 'select') {
      if (typeof value !== 'string') {
        throw new BadRequestException(
          `Field "${field.label}" expects a single option value`,
        );
      }
      this.findOptionByValue(field, value);
      return;
    }

    if (!Array.isArray(value) || !value.length) {
      throw new BadRequestException(
        `Field "${field.label}" expects an array of option values`,
      );
    }

    for (const item of value) {
      if (typeof item !== 'string') {
        throw new BadRequestException(
          `Field "${field.label}" expects string option values`,
        );
      }
      this.findOptionByValue(field, item);
    }
  }

  private findOptionByValue(field: FormField, rawValue: string) {
    const normalized = rawValue.trim().toLowerCase();
    const option =
      field.options.find((item) => item.value === rawValue) ??
      field.options.find((item) => item.value.toLowerCase() === normalized) ??
      field.options.find((item) => item.label.toLowerCase() === normalized);

    if (!option) {
      throw new BadRequestException(
        `Invalid option "${rawValue}" for field "${field.label}"`,
      );
    }

    return option;
  }

  private async loadProductValues(
    businessId: bigint,
    productId: bigint,
    fields: FormField[],
  ) {
    const fieldIds = fields.map((field) => BigInt(field.id));

    const stored = await this.prisma.productTechnicalFieldValue.findMany({
      where: {
        businessId,
        productId,
        fieldId: { in: fieldIds },
      },
      include: {
        option: true,
        selectedOptions: { include: { option: true } },
        field: true,
      },
    });

    const byFieldId = new Map(
      stored.map((item) => [item.fieldId.toString(), item]),
    );

    return fields.map((field) => {
      const record = byFieldId.get(field.id);
      if (!record) {
        return {
          fieldKey: field.key,
          fieldLabel: field.label,
          type: field.type,
          value:
            field.type === 'multi_select' || field.type === 'multi_value' ? [] : null,
        };
      }

      if (field.type === 'multi_value') {
        return {
          fieldKey: field.key,
          fieldLabel: field.label,
          type: field.type,
          value: decodeMultiValueText(record.textValue),
        };
      }

      if (field.type === 'text' || field.type === 'textarea') {
        return {
          fieldKey: field.key,
          fieldLabel: field.label,
          type: field.type,
          value: record.textValue,
        };
      }

      if (field.type === 'select') {
        return {
          fieldKey: field.key,
          fieldLabel: field.label,
          type: field.type,
          value: record.option?.value ?? null,
          optionLabel: record.option?.label ?? null,
        };
      }

      return {
        fieldKey: field.key,
        fieldLabel: field.label,
        type: field.type,
        value: record.selectedOptions.map((item) => item.option.value),
        optionLabels: record.selectedOptions.map((item) => item.option.label),
      };
    });
  }

  private async getProductWithCategory(businessId: bigint, productId: bigint) {
    const product = await this.prisma.product.findFirst({
      where: { id: productId, businessId },
    });

    if (!product) {
      throw new NotFoundException('Product not found');
    }

    const assignment = await this.prisma.categoryAssignment.findFirst({
      where: {
        businessId,
        entityType: MediaEntityType.product,
        entityId: productId,
      },
    });

    return {
      product,
      categoryId: assignment?.categoryId ?? null,
    };
  }

  private async assertPublishedProductExists(businessId: bigint, productId: bigint) {
    const product = await this.prisma.product.findFirst({
      where: {
        id: productId,
        businessId,
        status: ContentStatus.published,
      },
      select: { id: true },
    });

    if (!product) {
      throw new NotFoundException('Product not found');
    }
  }

  private async assertPermission(
    businessId: bigint,
    userId: bigint,
    permission: string,
  ) {
    const allowed = await this.permissions.hasBusinessPermission(
      userId,
      businessId,
      permission,
    );

    if (!allowed) {
      throw new ForbiddenException(
        `Missing permission: ${permission} for this business`,
      );
    }
  }
}