import XCTest

final class ViewDerivedDataTests: XCTestCase {
  func testGenericListViewDerivedCollectionsAreReferencedOncePerRenderPass() throws {
    let source = try loadSource(at: "Sora/Views/Generic/GenericListView.swift")
    let normalizedSource = strippingCommentsAndStrings(from: source)

    let filteredItemsUsages = referenceCount(
      for: "filteredItems",
      in: normalizedSource
    )
    let sortedFilteredItemsUsages = referenceCount(
      for: "sortedFilteredItems",
      in: normalizedSource
    )

    // swiftlint:disable:next prefer_nimble
    XCTAssertLessThanOrEqual(
      filteredItemsUsages,
      1,
      "filteredItems should be consumed once per dependency change."
    )
    // swiftlint:disable:next prefer_nimble
    XCTAssertLessThanOrEqual(
      sortedFilteredItemsUsages,
      1,
      "sortedFilteredItems should be consumed once per dependency change."
    )
  }

  func testPostGridViewDerivedCollectionsAreReferencedOncePerRenderPass() throws {
    let source = try loadSource(at: "Sora/Views/Post/Grid/PostGridView.swift")
    let normalizedSource = strippingCommentsAndStrings(from: source)

    let activePostsUsages = referenceCount(
      for: "activePosts",
      in: normalizedSource
    )
    let getColumnsDataUsages = invocationCount(
      forFunction: "getColumnsData",
      in: normalizedSource
    )

    // swiftlint:disable:next prefer_nimble
    XCTAssertLessThanOrEqual(
      activePostsUsages,
      1,
      "activePosts-derived data should be consumed once per dependency change."
    )
    // swiftlint:disable:next prefer_nimble
    XCTAssertLessThanOrEqual(
      getColumnsDataUsages,
      1,
      "getColumnsData should be invoked once per dependency change."
    )
  }

  private func referenceCount(for symbol: String, in source: String) -> Int {
    let totalMatches = tokenCount(
      matching: #"\b\#(symbol)\b"#,
      in: source
    )
    let declarationMatches = tokenCount(
      matching: #"\b(?:var|let)\s+\#(symbol)\b"#,
      in: source
    )

    return max(0, totalMatches - declarationMatches)
  }

  private func invocationCount(forFunction name: String, in source: String) -> Int {
    let totalMatches = tokenCount(
      matching: #"\b\#(name)\s*\("#,
      in: source
    )
    let declarationMatches = tokenCount(
      matching: #"\bfunc\s+\#(name)\s*\("#,
      in: source
    )

    return max(0, totalMatches - declarationMatches)
  }
}