import { describe, it, expect, vi, beforeEach } from 'vitest'
import fc from 'fast-check'
import { MigrationRoute } from '../../app/domain/firmware/firmware_catalog.js'

/**
 * Property 13: Firmware migration path resolution
 * Validates: Requirements 7.3
 *
 * Verifies that:
 * 1. If currentVersion === targetVersion, result is always empty array
 * 2. If a direct route exists from current to target, path has exactly 1 step
 * 3. Path steps are contiguous: step[i].toVersion === step[i+1].fromVersion
 * 4. No version appears twice in the path (no cycles)
 * 5. First step starts from currentVersion, last step ends at targetVersion (when path exists)
 */

vi.mock('../../app/models/migration_route.js', () => ({
  default: {
    findByProductClass: vi.fn(),
  },
}))

vi.mock('../../app/models/firmware_entry.js', () => ({
  default: {
    findByProductClassAndVersion: vi.fn(),
  },
}))

import MigrationRouteModel from '../../app/models/migration_route.js'
import FirmwareEntryModel from '../../app/models/firmware_entry.js'
import FirmwareCatalogService from '../../app/services/firmware_catalog_service.js'

describe('Property 13: Firmware migration path resolution', () => {
  let service: FirmwareCatalogService

  beforeEach(() => {
    service = new FirmwareCatalogService()
    vi.mocked(MigrationRouteModel.findByProductClass).mockReset()
    vi.mocked(FirmwareEntryModel.findByProductClassAndVersion).mockReset()
    vi.mocked(FirmwareEntryModel.findByProductClassAndVersion).mockResolvedValue(null)
  })

  /**
   * Arbitrary for version strings (e.g., "1.0.0", "2.3.1")
   */
  const versionArb = fc
    .tuple(
      fc.integer({ min: 0, max: 99 }),
      fc.integer({ min: 0, max: 99 }),
      fc.integer({ min: 0, max: 99 })
    )
    .map(([major, minor, patch]) => `${major}.${minor}.${patch}`)

  /**
   * Arbitrary for productClass strings
   */
  const productClassArb = fc.stringMatching(/^[A-Za-z][A-Za-z0-9]{2,10}$/)

  /**
   * Helper to create a MigrationRoute object
   */
  function makeRoute(
    productClass: string,
    sourceVersionPattern: string,
    targetVersion: string,
    priority: number = 10
  ): MigrationRoute {
    return {
      identifier: `${productClass}-${sourceVersionPattern}-to-${targetVersion}`,
      productClass,
      sourceVersionPattern,
      targetVersion,
      downloadUrl: `http://firmware.local/${productClass}/${targetVersion}.bin`,
      priority,
      createdAt: new Date(),
    }
  }

  /**
   * Helper to set up mocks for a given set of routes
   */
  function setupMocks(routes: MigrationRoute[]) {
    vi.mocked(MigrationRouteModel.findByProductClass).mockImplementation(
      async (pc: string) => routes.filter((r) => r.productClass === pc)
    )
  }

  it('1. If currentVersion === targetVersion, result is always empty array', async () => {
    await fc.assert(
      fc.asyncProperty(productClassArb, versionArb, async (productClass, version) => {
        setupMocks([])
        const result = await service.resolveUpgradePath(productClass, version, version)
        expect(result).toEqual([])
      })
    )
  })

  it('2. If a direct route exists from current to target, path has exactly 1 step', async () => {
    await fc.assert(
      fc.asyncProperty(
        productClassArb,
        versionArb,
        versionArb,
        fc.integer({ min: 1, max: 100 }),
        async (productClass, currentVersion, targetVersion, priority) => {
          fc.pre(currentVersion !== targetVersion)

          const route = makeRoute(productClass, currentVersion, targetVersion, priority)
          setupMocks([route])

          const result = await service.resolveUpgradePath(
            productClass,
            currentVersion,
            targetVersion
          )
          expect(result).toHaveLength(1)
          expect(result[0].fromVersion).toBe(currentVersion)
          expect(result[0].toVersion).toBe(targetVersion)
        }
      )
    )
  })

  it('3. Path steps are contiguous: step[i].toVersion === step[i+1].fromVersion', async () => {
    /**
     * Generate a chain of distinct versions and create routes forming a linear path.
     */
    const distinctVersionsArb = fc
      .array(versionArb, { minLength: 3, maxLength: 6 })
      .map((versions) => [...new Set(versions)])
      .filter((unique) => unique.length >= 3)

    await fc.assert(
      fc.asyncProperty(productClassArb, distinctVersionsArb, async (productClass, versionList) => {
        // Create a chain of routes: v0→v1, v1→v2, ..., v(n-2)→v(n-1)
        const routes: MigrationRoute[] = []
        for (let i = 0; i < versionList.length - 1; i++) {
          routes.push(makeRoute(productClass, versionList[i], versionList[i + 1], 10))
        }

        setupMocks(routes)

        const currentVersion = versionList[0]
        const targetVersion = versionList[versionList.length - 1]

        const result = await service.resolveUpgradePath(
          productClass,
          currentVersion,
          targetVersion
        )

        // Path should be found and contiguous
        expect(result.length).toBeGreaterThan(0)
        for (let i = 0; i < result.length - 1; i++) {
          expect(result[i].toVersion).toBe(result[i + 1].fromVersion)
        }
      })
    )
  })

  it('4. No version appears twice in the path (no cycles)', async () => {
    const distinctVersionsArb = fc
      .array(versionArb, { minLength: 2, maxLength: 6 })
      .map((versions) => [...new Set(versions)])
      .filter((unique) => unique.length >= 2)

    await fc.assert(
      fc.asyncProperty(productClassArb, distinctVersionsArb, async (productClass, versionList) => {
        // Create routes forming a chain
        const routes: MigrationRoute[] = []
        for (let i = 0; i < versionList.length - 1; i++) {
          routes.push(makeRoute(productClass, versionList[i], versionList[i + 1], 10))
        }

        setupMocks(routes)

        const currentVersion = versionList[0]
        const targetVersion = versionList[versionList.length - 1]

        const result = await service.resolveUpgradePath(
          productClass,
          currentVersion,
          targetVersion
        )

        // Collect all versions in the path
        if (result.length > 0) {
          const allVersions: string[] = [result[0].fromVersion]
          for (const step of result) {
            allVersions.push(step.toVersion)
          }
          // No duplicates
          const uniqueVersions = new Set(allVersions)
          expect(uniqueVersions.size).toBe(allVersions.length)
        }
      })
    )
  })

  it('5. First step starts from currentVersion, last step ends at targetVersion (when path exists)', async () => {
    const distinctVersionsArb = fc
      .array(versionArb, { minLength: 2, maxLength: 6 })
      .map((versions) => [...new Set(versions)])
      .filter((unique) => unique.length >= 2)

    await fc.assert(
      fc.asyncProperty(productClassArb, distinctVersionsArb, async (productClass, versionList) => {
        // Create routes forming a chain
        const routes: MigrationRoute[] = []
        for (let i = 0; i < versionList.length - 1; i++) {
          routes.push(makeRoute(productClass, versionList[i], versionList[i + 1], 10))
        }

        setupMocks(routes)

        const currentVersion = versionList[0]
        const targetVersion = versionList[versionList.length - 1]

        const result = await service.resolveUpgradePath(
          productClass,
          currentVersion,
          targetVersion
        )

        if (result.length > 0) {
          expect(result[0].fromVersion).toBe(currentVersion)
          expect(result[result.length - 1].toVersion).toBe(targetVersion)
        }
      })
    )
  })

  it('cycle detection: routes forming a cycle return empty path', async () => {
    await fc.assert(
      fc.asyncProperty(
        productClassArb,
        versionArb,
        versionArb,
        versionArb,
        async (productClass, v1, v2, target) => {
          // Ensure all three are distinct
          fc.pre(v1 !== v2 && v2 !== target && v1 !== target)

          // Create a cycle: v1→v2, v2→v1 (cycle), no route to target
          const routes: MigrationRoute[] = [
            makeRoute(productClass, v1, v2, 10),
            makeRoute(productClass, v2, v1, 10),
          ]

          setupMocks(routes)

          const result = await service.resolveUpgradePath(productClass, v1, target)
          // Should return empty (either no path to target, or cycle detected)
          expect(result).toEqual([])
        }
      )
    )
  })
})