;; Phase 3 — ranking (TF-IDF, BM25, top-N). Deterministic: ties broken by DocId.
;; Corpora:
;;   idx1: 1 "alpha alpha alpha gamma"  2 "alpha"  3 "beta"
;;   idx2: 1 "cat"  2 "cat cat dog elephant frog grape"  3 "zzz"
;;   idx3: 1 "kite"  2 "kite"   (identical docs -> tiebreak)

(define
  rank-setup
  "idx1 = indexDoc 3 \"beta\" (indexDoc 2 \"alpha\" (indexDoc 1 \"alpha alpha alpha gamma\" emptyIndex))\nidx2 = indexDoc 3 \"zzz\" (indexDoc 2 \"cat cat dog elephant frog grape\" (indexDoc 1 \"cat\" emptyIndex))\nidx3 = indexDoc 2 \"kite\" (indexDoc 1 \"kite\" emptyIndex)\n")

(define
  rank-cases
  (list
    (list
      "tfidf tf ordering"
      "rankTfIdf [\"alpha\"] idx1"
      (list 1 2))
    (list
      "tfidf rare term boosts"
      "rankTfIdf [\"alpha\", \"beta\"] idx1"
      (list 1 3 2))
    (list
      "tfidf single-doc term"
      "rankTfIdf [\"gamma\"] idx1"
      (list 1))
    (list "tfidf absent term empty" "rankTfIdf [\"nope\"] idx1" (list))
    (list "tfidf empty query empty" "rankTfIdf [] idx1" (list))
    (list
      "tfidf candidate union tie by docid"
      "rankTfIdf [\"beta\", \"gamma\"] idx1"
      (list 1 3))
    (list
      "tfidf tf ordering idx2"
      "rankTfIdf [\"cat\"] idx2"
      (list 2 1))
    (list "topN tfidf 1" "topNTfIdf 1 [\"alpha\"] idx1" (list 1))
    (list
      "topN tfidf 2"
      "topNTfIdf 2 [\"alpha\", \"beta\"] idx1"
      (list 1 3))
    (list
      "topN exceeds results"
      "topNTfIdf 10 [\"gamma\"] idx1"
      (list 1))
    (list "topN zero" "topNTfIdf 0 [\"alpha\"] idx1" (list))
    (list
      "bm25 tf+length flips tfidf"
      "rankBm25 1.5 0.75 [\"cat\"] idx2"
      (list 1 2))
    (list
      "bm25 b=0 ignores length"
      "rankBm25 1.5 0.0 [\"cat\"] idx2"
      (list 2 1))
    (list
      "bm25 alpha idx1"
      "rankBm25 1.5 0.75 [\"alpha\"] idx1"
      (list 1 2))
    (list "bm25 absent empty" "rankBm25 1.5 0.75 [\"nope\"] idx1" (list))
    (list
      "bm25 single-doc term"
      "rankBm25 1.5 0.75 [\"gamma\"] idx1"
      (list 1))
    (list "bm25 topN 1" "topNBm25 1 1.5 0.75 [\"cat\"] idx2" (list 1))
    (list
      "bm25 same candidate set"
      "sort (rankBm25 1.5 0.75 [\"alpha\", \"beta\"] idx1)"
      (list 1 2 3))
    (list
      "tfidf stable tiebreak"
      "rankTfIdf [\"kite\"] idx3"
      (list 1 2))
    (list
      "bm25 stable tiebreak"
      "rankBm25 1.5 0.75 [\"kite\"] idx3"
      (list 1 2))
    (list "numDocs" "[numDocs idx1]" (list 3))
    (list "docLen counts tokens" "[docLen 1 idx1]" (list 4))
    (list "docFreq via index" "[docFreq \"alpha\" idx1]" (list 2))))

(define
  rank-results
  (search-batch rank-setup (map (fn (c) (nth c 1)) rank-cases)))

(map-indexed
  (fn
    (i c)
    (hk-test (nth c 0) (nth rank-results i) (nth c 2)))
  rank-cases)

{:fail hk-test-fail :pass hk-test-pass :fails hk-test-fails}