import ConfigurationModel from '#models/configuration'
import DeviceModel from '#models/device'
import FirmwareCatalogService from './firmware_catalog_service.js'
import type { Configuration, ParameterCriteria, ParameterValueType } from '../domain/configuration/configuration.js'
import type { Device } from '../domain/device/device.js'
import type { MigrationStep } from '../domain/firmware/migration_step.js'
import { isWithinSchedule } from '../utils/schedule_window.js'
import { matchGlob } from '../utils/glob_match.js'
import { computeContentHash, parseProvisioningCode } from '../utils/provisioning_code.js'

export interface ComplianceDeviceResult {
  identifier: string
  deviceId: any
  compliant: boolean
  parameterDiffs: ParameterDiff[]
  firmwareMigrationPath: MigrationStep[]
}

export interface ComplianceReport {
  configurationId: string
  configurationName: string
  totalDevices: number
  compliantCount: number
  nonCompliantCount: number
  devices: ComplianceDeviceResult[]
}

/**
 * Result of a single device configuration evaluation.
 * Contains all the actions to be executed by the state machine.
 */
export interface EngineResult {
  configuration: Configuration | null
  inventoryPaths: string[]
  parameterDiffs: ParameterDiff[]
  firmwareMigrationPath: MigrationStep[]
  isAlreadyCompliant: boolean
  skipFirmware: boolean // true if outside schedule window
}

/**
 * A single parameter difference (desired vs current).
 */
export interface ParameterDiff {
  name: string
  currentValue: string | number | boolean | null
  targetValue: string | number | boolean
  type: ParameterValueType
}

/**
 * Result of a dry-run evaluation.
 */
export interface DryRunResult {
  configurationId: string
  deviceIdentifier: string
  evaluation: EngineResult
  timestamp: Date
}

/**
 * ConfigurationEngine evaluates device compliance against configurations.
 * 
 * Responsibilities:
 * - Find matching enabled configurations for a device
 * - Select the highest priority configuration
 * - Compute parameter differences (desired vs current)
 * - Handle policy "once" via ProvisioningCode comparison
 * - Resolve firmware migration paths
 * - Check schedule windows for firmware operations
 */
export default class ConfigurationEngine {
  private firmwareService: FirmwareCatalogService

  constructor() {
    this.firmwareService = new FirmwareCatalogService()
  }

  /**
   * Evaluate device compliance against all matching configurations.
   * 
   * Steps:
   * 1. Load all enabled configurations
   * 2. Filter by criteria (glob matching against DeviceId)
   * 3. Select highest priority configuration
   * 4. Check if already compliant via ProvisioningCode (policy "once")
   * 5. Compute parameter differences
   * 6. Resolve firmware migration path
   * 7. Check schedule window for firmware operations
   */
  async evaluate(device: Device): Promise<EngineResult> {
    // 1. Load all enabled configurations
    const allConfigs = await ConfigurationModel.find({ enabled: true })

    // 2. Filter by criteria (glob matching against DeviceId)
    const matchingConfigs = allConfigs.filter((config) => this.matchesCriteria(device, config))

    // 3. Select highest priority configuration
    let selectedConfig: Configuration | null = null
    if (matchingConfigs.length > 0) {
      selectedConfig = matchingConfigs.reduce((prev, curr) =>
        curr.priority > prev.priority ? curr : prev
      )
    }

    // If no matching configuration, device is already compliant (nothing to do)
    if (!selectedConfig) {
      return {
        configuration: null,
        inventoryPaths: [],
        parameterDiffs: [],
        firmwareMigrationPath: [],
        isAlreadyCompliant: true,
        skipFirmware: false,
      }
    }

    // 4. Check if already compliant via ProvisioningCode (policy "once")
    if (!this.shouldApplyOnce(device, selectedConfig)) {
      return {
        configuration: selectedConfig,
        inventoryPaths: [],
        parameterDiffs: [],
        firmwareMigrationPath: [],
        isAlreadyCompliant: true,
        skipFirmware: false,
      }
    }

    // 5. Compute parameter differences
    const parameterDiffs = await this.computeParameterDiffs(device, selectedConfig)

    // 6. Resolve firmware migration path
    let firmwareMigrationPath: MigrationStep[] = []
    let skipFirmware = false

    if (selectedConfig.firmwareTarget) {
      // Check schedule window for firmware operations
      if (!isWithinSchedule(selectedConfig.schedule)) {
        skipFirmware = true
      } else {
        // Get current device version (from properties or parameter)
        const currentVersion = this.getDeviceVersion(device, selectedConfig.firmwareTarget.productClass)

        if (currentVersion && currentVersion !== selectedConfig.firmwareTarget.targetVersion) {
          firmwareMigrationPath = await this.firmwareService.resolveUpgradePath(
            selectedConfig.firmwareTarget.productClass,
            currentVersion,
            selectedConfig.firmwareTarget.targetVersion
          )
        }
      }
    }

    // Check if compliant (no diffs and no firmware needed)
    const isCompliant =
      parameterDiffs.length === 0 && 
      firmwareMigrationPath.length === 0

    return {
      configuration: selectedConfig,
      inventoryPaths: selectedConfig.inventory.map((inv) => inv.path),
      parameterDiffs,
      firmwareMigrationPath,
      isAlreadyCompliant: isCompliant,
      skipFirmware,
    }
  }

  /**
   * Dry-run evaluation for a specific configuration on a device.
   * Similar to evaluate() but can be called explicitly by the user.
   */
  async dryRun(configId: string, deviceIdentifier: string): Promise<DryRunResult> {
    const configuration = await ConfigurationModel.findOne({ identifier: configId })
    if (!configuration) {
      throw new Error(`Configuration ${configId} not found`)
    }

    const device = await DeviceModel.findOne({
      $or: [{ identifier: deviceIdentifier }, { 'deviceId.id': deviceIdentifier }],
    })
    if (!device) {
      throw new Error(`Device ${deviceIdentifier} not found`)
    }

    // Check if configuration matches device criteria
    if (!this.matchesCriteria(device, configuration)) {
      throw new Error(`Configuration ${configId} does not match device ${deviceIdentifier}`)
    }

    const evaluation = await this.evaluateSpecific(device, configuration)

    return {
      configurationId: configId,
      deviceIdentifier,
      evaluation,
      timestamp: new Date(),
    }
  }

  /**
   * Evaluate a specific configuration against a device.
   * Used by dry-run, compliance check, and potentially other flows.
   */
  async evaluateSpecific(device: Device, config: Configuration): Promise<EngineResult> {
    // Check policy "once"
    if (!this.shouldApplyOnce(device, config)) {
      return {
        configuration: config,
        inventoryPaths: [],
        parameterDiffs: [],
        firmwareMigrationPath: [],
        isAlreadyCompliant: true,
        skipFirmware: false,
      }
    }

    // Compute parameter differences
    const parameterDiffs = await this.computeParameterDiffs(device, config)

    // Resolve firmware migration path
    let firmwareMigrationPath: MigrationStep[] = []
    let skipFirmware = false

    if (config.firmwareTarget) {
      if (!isWithinSchedule(config.schedule)) {
        skipFirmware = true
      } else {
        const currentVersion = this.getDeviceVersion(device, config.firmwareTarget.productClass)
        if (currentVersion && currentVersion !== config.firmwareTarget.targetVersion) {
          firmwareMigrationPath = await this.firmwareService.resolveUpgradePath(
            config.firmwareTarget.productClass,
            currentVersion,
            config.firmwareTarget.targetVersion
          )
        }
      }
    }

    const isCompliant = parameterDiffs.length === 0 && firmwareMigrationPath.length === 0

    return {
      configuration: config,
      inventoryPaths: config.inventory.map((inv) => inv.path),
      parameterDiffs,
      firmwareMigrationPath,
      isAlreadyCompliant: isCompliant,
      skipFirmware,
    }
  }

  /**
   * Check if a device matches all criteria of a configuration.
   * Uses glob matching for each criterion.
   */
  private matchesCriteria(device: Device, config: Configuration): boolean {
    const criteria = config.criteria

    // manufacturer
    if (criteria.manufacturer) {
      const deviceValue = device.deviceId.manufacturer || ''
      if (!matchGlob(criteria.manufacturer, deviceValue)) {
        return false
      }
    }

    // oui
    if (criteria.oui) {
      const deviceValue = device.deviceId.oui || ''
      if (!matchGlob(criteria.oui, deviceValue)) {
        return false
      }
    }

    // productClass
    if (criteria.productClass) {
      const deviceValue = device.deviceId.productClass || ''
      if (!matchGlob(criteria.productClass, deviceValue)) {
        return false
      }
    }

    // serialNumber
    if (criteria.serialNumber) {
      const deviceValue = device.deviceId.serialNumber || ''
      if (!matchGlob(criteria.serialNumber, deviceValue)) {
        return false
      }
    }

    // parameterCriteria: all conditions must match a known device parameter value
    if (Array.isArray(criteria.parameterCriteria) && criteria.parameterCriteria.length > 0) {
      const hasGetters = typeof (device as any).getParameters === 'function'
      const allParams = hasGetters
        ? [...(device as any).getParameters(), ...(device as any).getProperties()]
        : [...((device as any).parameters ?? []), ...((device as any).properties ?? [])]
      for (const pc of criteria.parameterCriteria as ParameterCriteria[]) {
        if (!pc.name) continue
        const known = allParams.find((p: any) => p.name === pc.name)
        if (known === undefined || known.value === null || known.value === undefined) {
          return false
        }
        if (String(known.value) !== String(pc.value)) {
          return false
        }
      }
    }

    return true
  }

  /**
   * Determine if policy "once" should allow application of the configuration.
   * 
   * - For policy "maintain": always apply
   * - For policy "once": apply if device doesn't have the provisioning code
   *   (indicating content has changed or never applied)
   */
  private shouldApplyOnce(device: Device, config: Configuration): boolean {
    if (config.policy === 'maintain') {
      return true
    }

    if (config.policy !== 'once') {
      return true
    }

    // For "once" policy, check if device has matching provisioning code
    const deviceProvCode = (device as any).provisioningCode
    if (!deviceProvCode) {
      return true // No provisioning code yet, apply it
    }

    // Parse the provisioning code
    const parsed = parseProvisioningCode(deviceProvCode)
    if (!parsed) {
      return true // Invalid format, re-apply
    }

    // Check if identifiers match and content hasn't changed
    if (parsed.identifier !== config.identifier) {
      return true // Different configuration, apply
    }

    const currentHash = computeContentHash(config)
    if (parsed.hash !== currentHash) {
      return true // Content changed, re-apply
    }

    // Same configuration, same content hash => already applied
    return false
  }

  /**
   * Compute parameter differences between desired and current state.
   */
  private async computeParameterDiffs(
    device: Device,
    config: Configuration
  ): Promise<ParameterDiff[]> {
    const diffs: ParameterDiff[] = []

    for (const desired of config.desiredParameters) {
      // Get current value from device
      const currentValue = this.getDeviceParameterValue(device, desired.name)

      // Compare values
      if (currentValue !== desired.value) {
        diffs.push({
          name: desired.name,
          currentValue,
          targetValue: desired.value,
          type: desired.type,
        })
      }
    }

    return diffs
  }

  /**
   * Get the current value of a parameter from the device.
   * Returns null if not found.
   */
  private getDeviceParameterValue(device: Device, paramName: string): string | number | boolean | null {
    // Try method-based access first (Device class instances)
    if (typeof (device as any).getParameter === 'function') {
      const param = (device as any).getParameter(paramName)
      if (param) {
        const value = param.value
        if (value === undefined || value === null) return null
        if (typeof value === 'boolean') return value
        if (typeof value === 'number') return value
        return String(value)
      }
      return null
    }

    // Fallback: plain DeviceRecord objects (parameters + properties arrays)
    const allEntries = [...((device as any).parameters ?? []), ...((device as any).properties ?? [])]
    const entry = allEntries.find((p: any) => p.name === paramName)
    if (!entry || entry.value === undefined || entry.value === null) return null
    if (typeof entry.value === 'boolean') return entry.value
    if (typeof entry.value === 'number') return entry.value
    return String(entry.value)
  }

  /**
   * Get the device's current firmware version.
   * Looks in device properties or parameters (e.g., "Device.DeviceInfo.SoftwareVersion")
   */
  private getDeviceVersion(device: Device, productClass: string): string | null {
    const versionParams = [
      'Device.DeviceInfo.SoftwareVersion',
      'InternetGatewayDevice.DeviceInfo.SoftwareVersion',
      `Device.${productClass}.FirmwareVersion`,
    ]
    for (const paramName of versionParams) {
      const value = this.getDeviceParameterValue(device, paramName)
      if (value && typeof value === 'string') {
        return value
      }
    }
    return null
  }

  /**
   * Generate a compliance report for a configuration.
   * Returns all devices matching the criteria with their compliance status.
   */
  async complianceReport(configId: string): Promise<ComplianceReport> {
    const configuration = await ConfigurationModel.findOne({ identifier: configId })
    if (!configuration) {
      throw new Error(`Configuration ${configId} not found`)
    }

    // Load all devices
    const collection = DeviceModel.getCollection()
    const allDevices = (await collection.find({}).toArray()) as unknown as Device[]

    // Filter by criteria
    const matchingDevices = allDevices.filter((d) => this.matchesCriteria(d, configuration))

    // Evaluate each matching device
    const devices: ComplianceDeviceResult[] = await Promise.all(
      matchingDevices.map(async (device) => {
        const evaluation = await this.evaluateSpecific(device, configuration)
        return {
          identifier: (device as any).identifier ?? (device as any).deviceId?.serialNumber ?? '?',
          deviceId: (device as any).deviceId,
          compliant: evaluation.isAlreadyCompliant,
          parameterDiffs: evaluation.parameterDiffs,
          firmwareMigrationPath: evaluation.firmwareMigrationPath,
        }
      })
    )

    return {
      configurationId: configId,
      configurationName: configuration.name,
      totalDevices: devices.length,
      compliantCount: devices.filter((d) => d.compliant).length,
      nonCompliantCount: devices.filter((d) => !d.compliant).length,
      devices,
    }
  }
}