From 452cb8f0faff770ff58e08cda736234c62d59eaf Mon Sep 17 00:00:00 2001
From: Ben Greenman <benjaminlgreenman@gmail.com>
Date: Tue, 2 Aug 2016 02:15:22 -0400
Subject: [PATCH] typed day22

---
 typed/day22.rkt | 206 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 206 insertions(+)
 create mode 100644 typed/day22.rkt

diff --git a/typed/day22.rkt b/typed/day22.rkt
new file mode 100644
index 0000000..dc770b5
--- /dev/null
+++ b/typed/day22.rkt
@@ -0,0 +1,206 @@
+#lang typed/racket
+
+(define BASE-HP 50)
+(define BASE-MANA 500)
+
+(define MAGIC-MISSILE-DAMAGE 4)
+(define DRAIN-DAMAGE 2)
+(define SHIELD-ARMOR 7)
+(define SHIELD-DURATION 6)
+(define POISON-DAMAGE 3)
+(define POISON-DURATION 6)
+(define RECHARGE-MANA 101)
+(define RECHARGE-DURATION 5)
+
+(struct player (
+  [hp : Integer]
+  [attack : Natural]
+  [mana : Integer]
+) #:transparent)
+(define-type Player player)
+
+(define-type Spell (U 'magic-missile 'drain 'shield 'poison 'recharge))
+(define-type Active-Spells (Listof (Pairof Natural Spell)))
+
+;(define-type Game-State (Values Player Player Active-Spells))
+
+(define ALL-SPELLS : (Listof Spell)
+  '(magic-missile
+    drain
+    shield
+    poison
+    recharge))
+
+(: unknown-spell (All (A) (-> Spell A)))
+(define (unknown-spell spell)
+  (raise-user-error 'day22 "Unknown spell '~a'" spell))
+
+(: spell-mana (-> Spell Natural))
+(define (spell-mana s)
+  (case s
+   [(magic-missile)
+    53]
+   [(drain)
+    73]
+   [(shield)
+    113]
+   [(poison)
+    173]
+   [(recharge)
+    229]
+   [else
+    (unknown-spell s)]))
+
+(: spell*-mana (-> (Listof Spell) Natural))
+(define (spell*-mana spell*)
+  (for/sum : Natural ([spell (in-list spell*)])
+    (spell-mana spell)))
+
+(: make-player (-> Player))
+(define (make-player)
+  (player BASE-HP 0 BASE-MANA))
+
+(: make-boss (-> Index * Player))
+(define (make-boss . val*)
+  (player (car val*) (cadr val*) 0))
+
+(: hp+ (-> Player Integer Player))
+(define (hp+ p val)
+  (match-define (player hp attack mana) p)
+  (player (+ hp val) attack mana))
+
+(: hp- (-> Player Integer Player))
+(define (hp- p val)
+  (hp+ p (- val)))
+
+(: mana+ (-> Player Integer Player))
+(define (mana+ p val)
+  (match-define (player hp attack mana) p)
+  (player hp attack (+ mana val)))
+
+(: mana- (-> Player Integer Player))
+(define (mana- p val)
+  (mana+ p (- val)))
+
+(: active? (-> Spell Active-Spells Boolean))
+(define (active? spell active-spells)
+  (for/or : Boolean
+          ([ctr+spell (in-list active-spells)])
+    (eq? spell (cdr ctr+spell))))
+
+(: has-enough-mana? (-> Player Spell Boolean))
+(define (has-enough-mana? player spell)
+  (<= (spell-mana spell) (player-mana player)))
+
+(: boss-attack (-> Player Player Boolean Player))
+(define (boss-attack player boss shield?)
+  (define boss-damage (max 1 (- (player-attack boss) (if shield? SHIELD-ARMOR 0))))
+  (hp- player boss-damage))
+
+(: apply-effects (-> Player Player (Listof (Pairof Natural Spell)) (Values Player Player Active-Spells)))
+(define (apply-effects player boss spells)
+  (for/fold ([p+ : Player player]
+             [b+ : Player boss]
+             [a+ : Active-Spells '()])
+            ([ctr+spell (in-list spells)])
+    (match-define (cons ctr spell) ctr+spell)
+    (define a++ (if (= 1 ctr) a+ (cons (cons (assert (- ctr 1) index?) spell) a+)))
+    (case spell
+     [(poison)
+      (values p+ (hp- b+ POISON-DAMAGE) a++)]
+     [(recharge)
+      (values (mana+ p+ RECHARGE-MANA) b+ a++)]
+     [(shield)
+      (values p+ b+ a++)]
+     [else
+      (unknown-spell spell)])))
+
+(: apply-spell (-> Spell Player Player Active-Spells (Values Player Player Active-Spells)))
+(define (apply-spell spell player0 boss active-spells)
+  (define player (mana- player0 (spell-mana spell)))
+  (case spell
+   [(magic-missile)
+    (values player (hp- boss MAGIC-MISSILE-DAMAGE) active-spells)]
+   [(drain)
+    (values (hp+ player DRAIN-DAMAGE) (hp- boss DRAIN-DAMAGE) active-spells)]
+   [(shield)
+    (values player boss (cons (cons SHIELD-DURATION 'shield) active-spells))]
+   [(poison)
+    (values player boss (cons (cons POISON-DURATION 'poison) active-spells))]
+   [(recharge)
+    (values player boss (cons (cons RECHARGE-DURATION 'recharge) active-spells))]
+   [else
+    (unknown-spell spell)]))
+
+(: win? (-> Player Player Boolean))
+(define (win? player boss)
+  (dead? boss))
+
+(: dead? (-> Player Boolean))
+(define (dead? player)
+  (<= (player-hp player) 0))
+
+(: lose? (-> Player Player Boolean))
+(define lose?
+  (let ([MIN-MANA (apply min (map spell-mana ALL-SPELLS))])
+    (λ (player boss)
+      (or (dead? player)
+          (< (player-mana player) MIN-MANA)))))
+
+(: win/least-mana : Player Player [#:hard-mode? Boolean] -> (Listof Spell))
+(define (win/least-mana player boss #:hard-mode? [hard-mode? #f])
+  (or
+    (let maybe-win/least-mana : (U #f (Listof Spell))
+                              ([player : Player player]
+                               [boss : Player boss]
+                               [active-spells : Active-Spells '()]
+                               [current-turn : Natural 0])
+      (cond
+       [(lose? player boss)
+        #f]
+       [(win? player boss)
+        '()]
+       [else
+        (define-values (p+ b+ a+) (apply-effects player boss active-spells))
+        (define next-turn (+ 1 current-turn))
+        (if (even? current-turn)
+          (let ([p+ (if hard-mode? (hp- p+ 1) p+)])
+            (minimize-mana
+              (for/list : (Listof (U #f (Listof Spell)))
+                       ([spell (in-list ALL-SPELLS)]
+                       #:when (and (not (active? spell a+))
+                                   (has-enough-mana? p+ spell)))
+                (define-values (p++ b++ a++) (apply-spell spell p+ b+ a+))
+                (define future-spells (maybe-win/least-mana p++ b++ a++ next-turn))
+                (and future-spells (cons spell future-spells)))))
+          (maybe-win/least-mana (boss-attack p+ b+ (active? 'shield a+)) b+ a+ next-turn))]))
+      (raise-user-error 'day22 "Impossible for ~a to beat ~a. Sorry.\n" player boss)))
+
+(: minimize-mana (-> (Listof (U #f (Listof Spell))) (U #f (Listof Spell))))
+(define (minimize-mana spell**)
+  (for/fold : (U #f (Listof Spell))
+            ([best : (U #f (Listof Spell)) #f])
+            ([other : (U #f (Listof Spell)) (in-list spell**)])
+    (if (or (not best)
+            (and best other (< (spell*-mana other) (spell*-mana best))))
+      other
+      best)))
+
+(: q1 (-> String Integer))
+(define (q1 input-str)
+  (define player (make-player))
+  (define boss (apply make-boss (filter index? (map string->number (string-split input-str)))))
+  (spell*-mana (win/least-mana player boss)))
+
+(: q2 (-> String Integer))
+(define (q2 input-str)
+  (define player (make-player))
+  (define boss (apply make-boss (filter index? (map string->number (string-split input-str)))))
+  (spell*-mana (win/least-mana player boss #:hard-mode? #t)))
+
+(module+ test
+  (require typed/rackunit)
+  (define input-str (file->string "../day22-input.txt"))
+  (check-equal? (q1 input-str) 1269)
+  (check-equal? (q2 input-str) 1309))
+