import FirmwareEntryModel from '#models/firmware_entry'
import MigrationRouteModel from '#models/migration_route'
import { FirmwareEntry, MigrationRoute } from '../domain/firmware/firmware_catalog.js'
import { MigrationStep } from '../domain/firmware/migration_step.js'
import { matchGlob } from '../utils/glob_match.js'
import { BadRequestException } from '../exceptions/index.js'

export interface CreateFirmwareEntryDto {
  identifier: string
  productClass: string
  version: string
  downloadUrl: string
  checksum: string
  checksumType: 'md5' | 'sha256'
  fileSize: number
}

export interface CreateMigrationRouteDto {
  identifier: string
  productClass: string
  sourceVersionPattern: string
  targetVersion: string
  downloadUrl: string
  priority: number
}

export default class FirmwareCatalogService {
  /**
   * Validate that a string is a valid URL.
   */
  private validateUrl(url: string, fieldName: string): void {
    try {
      new URL(url)
    } catch {
      throw new BadRequestException(`${fieldName} must be a valid URL`)
    }
  }

  /**
   * Validate that a number is a positive integer (> 0).
   */
  private validatePositiveInteger(value: number, fieldName: string): void {
    if (!Number.isInteger(value) || value <= 0) {
      throw new BadRequestException(`${fieldName} must be a positive integer`)
    }
  }

  /**
   * Validate that a string is non-empty.
   */
  private validateNonEmptyString(value: string, fieldName: string): void {
    if (!value || value.trim().length === 0) {
      throw new BadRequestException(`${fieldName} must be a non-empty string`)
    }
  }

  /**
   * Validate checksumType is 'md5' or 'sha256'.
   */
  private validateChecksumType(value: string, fieldName: string): void {
    if (value !== 'md5' && value !== 'sha256') {
      throw new BadRequestException(`${fieldName} must be 'md5' or 'sha256'`)
    }
  }

  /**
   * Create a new firmware entry after validation.
   */
  async createEntry(data: CreateFirmwareEntryDto): Promise<FirmwareEntry> {
    this.validateNonEmptyString(data.identifier, 'identifier')
    this.validateUrl(data.downloadUrl, 'downloadUrl')
    this.validatePositiveInteger(data.fileSize, 'fileSize')
    this.validateChecksumType(data.checksumType, 'checksumType')

    return FirmwareEntryModel.createIfNotExists({
      identifier: data.identifier,
      productClass: data.productClass,
      version: data.version,
      downloadUrl: data.downloadUrl,
      checksum: data.checksum,
      checksumType: data.checksumType,
      fileSize: data.fileSize,
    })
  }

  /**
   * Find firmware entries, optionally filtered by productClass.
   */
  async findEntries(productClass?: string): Promise<FirmwareEntry[]> {
    if (productClass) {
      return FirmwareEntryModel.findByProductClass(productClass)
    }
    return FirmwareEntryModel.find({}) as unknown as Promise<FirmwareEntry[]>
  }

  /**
   * Delete a firmware entry by identifier.
   */
  async deleteEntry(identifier: string): Promise<void> {
    const deleted = await FirmwareEntryModel.deleteByIdentifier(identifier)
    if (!deleted) {
      throw new BadRequestException(`Firmware entry '${identifier}' not found`)
    }
  }

  /**
   * Create a new migration route after validation.
   */
  async createMigrationRoute(data: CreateMigrationRouteDto): Promise<MigrationRoute> {
    this.validateNonEmptyString(data.identifier, 'identifier')
    this.validateUrl(data.downloadUrl, 'downloadUrl')
    this.validatePositiveInteger(data.priority, 'priority')

    return MigrationRouteModel.createIfNotExists({
      identifier: data.identifier,
      productClass: data.productClass,
      sourceVersionPattern: data.sourceVersionPattern,
      targetVersion: data.targetVersion,
      downloadUrl: data.downloadUrl,
      priority: data.priority,
    })
  }

  async findAllRoutes(): Promise<MigrationRoute[]> {
    return MigrationRouteModel.find({}) as unknown as Promise<MigrationRoute[]>
  }

  async updateEntry(identifier: string, data: Partial<CreateFirmwareEntryDto>): Promise<FirmwareEntry> {
    const collection = FirmwareEntryModel.getCollection()
    const result = await collection.findOneAndUpdate(
      { identifier },
      { $set: data },
      { returnDocument: 'after' }
    )
    if (!result) throw new BadRequestException(`Firmware entry '${identifier}' not found`)
    return result as unknown as FirmwareEntry
  }

  /**
   * Find migration routes for a productClass, sorted by priority descending.
   */
  async findMigrationRoutes(productClass: string): Promise<MigrationRoute[]> {
    return MigrationRouteModel.findByProductClass(productClass, { priority: -1 })
  }

  /**
   * Delete a migration route by identifier.
   */
  async deleteMigrationRoute(identifier: string): Promise<void> {
    const deleted = await MigrationRouteModel.deleteByIdentifier(identifier)
    if (!deleted) {
      throw new BadRequestException(`Migration route '${identifier}' not found`)
    }
  }

  /**
   * Resolve the firmware upgrade path from currentVersion to targetVersion.
   * Uses a greedy best-first algorithm based on route priority with cycle detection.
   *
   * @returns MigrationStep[] ordered from first to last, or [] if no path exists
   */
  async resolveUpgradePath(
    productClass: string,
    currentVersion: string,
    targetVersion: string
  ): Promise<MigrationStep[]> {
    // Trivial case: already at target version
    if (currentVersion === targetVersion) return []

    // Load all routes for this productClass
    const routes = await MigrationRouteModel.findByProductClass(productClass)

    const path: MigrationStep[] = []
    const visited = new Set<string>()
    let version = currentVersion

    visited.add(version)

    while (version !== targetVersion) {
      // Find all applicable routes from the current version
      const applicableRoutes = routes
        .filter((r) => matchGlob(r.sourceVersionPattern, version))
        .sort((a, b) => b.priority - a.priority) // Highest priority first

      // Take the best route (highest priority)
      const bestRoute = applicableRoutes[0]
      if (!bestRoute) {
        // No route found → no path exists
        return []
      }

      // Cycle detection
      if (visited.has(bestRoute.targetVersion)) {
        return []
      }

      // Add step to path
      path.push({
        fromVersion: version,
        toVersion: bestRoute.targetVersion,
        downloadUrl: bestRoute.downloadUrl,
        fileSize: 0,
        checksum: '',
      })

      // Advance
      visited.add(bestRoute.targetVersion)
      version = bestRoute.targetVersion
    }

    // Enrich each step with fileSize and checksum from firmware_entries
    for (const step of path) {
      const entry = await FirmwareEntryModel.findByProductClassAndVersion(
        productClass,
        step.toVersion
      )
      if (entry) {
        step.fileSize = entry.fileSize
        step.checksum = entry.checksum
      }
    }

    return path
  }
}