#include "boggle.h"
#include <string.h>
#include <timer.h>

enum {   kMinLen=3,               // no points for words < kMinLen
      kMaxDim=7,
      kMaxDimSquare=kMaxDim*kMaxDim,
      kHuge=127};

enum {   kPenaltyRate=20000,   // 20msec per point
      kFirstRun=32,
       kDefRiskFactor=13};      // 12 or 13 seem to work best

struct Timer {                  // microseconds system timer
 int T0;
 void StartTimer() {
  UnsignedWide UWT;
  Microseconds(&UWT);
  T0=UWT.lo;
 }
 int ReadTimer(){
  UnsignedWide UWT;
  Microseconds(&UWT);
  return UWT.lo-T0;
 }
};

GetProfile
// A word profile is a 32-bit bit map of letters used in word
static unsigned long GetProfile(const char* word,int num) {
 unsigned long p=0;
 for (int i=0;i<num;i++) {
  p |= 1<<(*word++ & 31);
 }
 return p;
}

static unsigned long GetProfile(const char* word) {
 int c;
 unsigned long p=0;
 while (0 != (c=*word++)) {
  p |= 1<<(c & 31);
 }
 return p;
}

Candidate
struct Candidate {   // A dictionary word that could fit
 const char*       word;
 unsigned long      profile;
 unsigned short   value;
 unsigned char      fit;
 unsigned char      tempFit;
 Candidate(){};

 Candidate(int len,const char* wd){
  word=wd;
  profile=GetProfile(wd);
  switch(len){
case 0:
case 1:
case 2:   value=0;break;
case 3:   
case 4:   value=1;break;
case 5:   value=2;break;
case 6:   value=3;break;
default:value=5+6*(len-7);
  }
  fit=tempFit=0;
 }
};

Neighbors
struct Neighbors {   
 char* next[9];   // pointers to the 8 neighbors of
};                              // a puzzle field, plus a NULL

enum {MIDDLE,EDGE,CORNER};
struct Neighborhood {   
 Neighbors nb[kMaxDimSquare]; // 1 set per puzzle field
 void Init(int dim,char* c) {
  int dimSq=dim*dim;
  int col,row,x=0;
  Setup(x++,c++,1,dim,CORNER);
  for (col=1;col<dim-1;col++) Setup(x++,c++,1,dim,EDGE);
  Setup(x++,c++,-1,dim,CORNER);
  for (row=1;row<dim-1;row++) {
   Setup(x++,c++,dim,1,EDGE);
   for (col=1;col<dim-1;col++) Setup(x++,c++,1,dim,MIDDLE);
   Setup(x++,c++,dim,-1,EDGE);
  }
  Setup(x++,c++,1,-dim,CORNER);
  for (col=1;col<dim-1;col++) Setup(x++,c++,1,-dim,EDGE);
  Setup(x++,c++,-1,-dim,CORNER);
 }
 void Setup(int from,char* c,int A,int B,int type) {
  char** np=nb[from].next;
  switch (type) {
case MIDDLE:
  *np++=c-A-B;
  *np++=c-B;
  *np++=c+A-B;
case EDGE:
  *np++=c-A;
  *np++=c-A+B;
case CORNER:
  *np++=c+A;
  *np++=c+B;
  *np++=c+A+B;
  *np=0;
  }
 }
};

Tour
struct Tour { // Sequence of puzzle locations
 char* tour[1+kMaxDimSquare];
 void Clear(){tour[0]=0;}
 void Add(char* loc) {
  char** tp=tour;
  while (*tp) tp++;
  *tp=loc;
  *++tp=0;
 }
 void Replace(char* loc1,char* loc2) {
  char** tp=tour;
  while (*tp) {
   if (*tp==loc1) {
    *tp=loc2;
    return;
   }
   tp++;
  }
  return;
 }
};

Stack
struct Stack {   // used to remember the track when
 char** CP;      // tracing a word through the puzzle
 char   val;
 void Push(char** c,char v){CP=c;val=v;}
 void Pop(char** & c,char & v){c=CP;v=val;}
};

Puzzle
struct Puzzle {
 int       dimension;            // 4 to 7
 int      dimSquare;            // 16 to 49
 int      points;               // computed points
 int      riskFactor;
 unsigned    long profile;   // of letters in puzzle      
 Stack*    SP;   
 char*    P;                        // ref to the 'puzzle'
 Timer      tmr;               
 char      letterCount[32];      
 int       energy[kMaxDimSquare];   // energy of puzzle fields
 Stack    stack[kMaxDimSquare];
 Tour      TOUR[32];                  // list of puzzle fields
 Neighborhood N;
 int      pairs[32*32];               // values of letter pairs

Puzzle::Init
 void    Init(int dim,char* puzzle) {
  dimension=dim;
  dimSquare=dim*dim;
  points=0;
  SP=stack;
  P=puzzle;
  memset(letterCount,0,32);
  for (int i=0;i<32;i++) TOUR[i].Clear();
  for (int i=0;i<dimSquare;i++) {
   char c=P[i];
   letterCount[c&31]++;
   TOUR[c&31].Add(P+i);
  }
  profile=GetProfile(P,dimSquare);
  N.Init(dimension,P);
  riskFactor=kDefRiskFactor-dim;   // more risk for larger puzzles
 }

Puzzle::Trace
 int Trace(Candidate* cd) { // trace 1 word
  const char* wd=cd->word;
  char** tour=TOUR[*wd & 31].tour;
  char* loc=*tour;
   char letter;
   
   // loop unrolled for the first and second letters of the word
first:
    letter=*loc;
   if (letter=='Q') ++wd;      //skip 'U' after 'Q'

   // deal with the first and second letters
   SP++->Push(tour,letter);
   *loc=0;               //hide 1st letter
   tour=N.nb[loc-P].next;      //goto 2nd tour
   loc=*tour; ++wd;
second:
   letter=*loc;
   if (letter==*wd) {
      if (letter=='Q') ++wd;      //skip 'U' after 'Q'
      if (wd[1]==0) goto success;
      SP++->Push(tour,letter);   
      *loc=0;                        //hide 2nd letter
      tour=N.nb[loc-P].next;   
      loc=*tour;   ++wd;
      goto third;                     //goto 3rd tour
   } else {
    loc=*++tour;            // next 2nd loc
      if (loc) goto second;
      
     (--SP)->Pop(tour,letter);
       **tour=letter;               //restore first letter
       if (letter=='Q') --wd;
       --wd;
       loc=*++tour;
       if (loc) goto first;
   }
   return 0;                  //fail

third:
  do {
   letter=*loc;
   if (letter==*wd) {
      if (letter=='Q') ++wd;      //skip 'U' after 'Q'
      if (wd[1]==0) break;         //success
      SP++->Push(tour,letter);   
      *loc=0;               //hide this letter
      tour=N.nb[loc-P].next;
      loc=*tour;   ++wd;
   } else do {
      loc=*++tour;
      if (loc==0) {
      if (SP<=stack) {
       return 0;
      }
      (--SP)->Pop(tour,letter);
        **tour=letter;            //restore last hidden letter
        if (letter=='Q') --wd;
        --wd;
      } else break;
   } while(1);
  } while(1);
success:
  while (SP>stack) {         // restore all letters
   (--SP)->Pop(tour,letter);
    **tour=letter;
    loc=*tour;
  }
  return 1;
 }

Puzzle::IsPossible
 int IsPossible(const char* word) {// all letters present
  int c,len=0;
  char myDist[32];
  memset(myDist,0,32);
  while (0 != (c=31 & *word++)) {   
   if (letterCount[c]>myDist[c]) {
    myDist[c]++;
    len++;
   } else return 0;
   if ((c==(31 & 'Q')) && (*word))
    word++;                        // don't need U after Q
  }
  return len;
 }

Puzzle::Swap
 void Swap(const int a,const int b){
  char ca=P[a],cb=P[b];
  TOUR[ca&31].Replace(P+a,P+b);
  TOUR[cb&31].Replace(P+b,P+a);
  P[a]=cb;
  P[b]=ca;
 }

// The next set of functions are for points maximization

Puzzle::RandomShake
// RandomShake just swaps two letters in the puzzle,
// making sure they are different, and returns the
// profile of the two letters
 unsigned long RandomShake(int & a,int & b) {
  char ca,cb;
  do {
   a=rand()%dimSquare;
   b=rand()%dimSquare;
  } while ((a==b) || ((ca=P[a])==(cb=P[b])));
  TOUR[ca&31].Replace(P+a,P+b);
  TOUR[cb&31].Replace(P+b,P+a);
  P[a]=cb;
  P[b]=ca;
  unsigned long shakeProfile=(1L<<(ca&31)) | (1L<<(cb&31));
  return shakeProfile;
 }

Puzzle::Evaluate
// The function Evaluate checks all candidates for fit,
// and computes the total point score for the puzzle
 void Evaluate(Candidate* cd,int numCandidates) {
  int pts=0;
  for (int i=0;i<numCandidates;i++) {
   if (0 != (cd->fit=Trace(cd))) {   
     pts+=cd->value;
   }   
   cd++;   
  }      
  points=pts;   
 }

Puzzle::Improves
// Improves() answers the question: would the proposed shakup
// increase the score. Computes candidates.tempFit.
// Uses shakeProfile to avoid recomputing candidates that
// are unaffected by the swap.
 bool Improves(
    unsigned long shakeProfile,
    Candidate* cd,int numCandidates) {
  int pts=points;
  for (int i=0;i<numCandidates;i++) {      
   if ((shakeProfile & cd->profile)) {   
    cd->tempFit=Trace(cd);
    pts+=(cd->tempFit-cd->fit)*cd->value;
   } else {
    cd->tempFit=cd->fit;
   }
   cd++;
  }
  if (pts>points) {
   points=pts;
   return true;
  }                  
  return false;
 }

Puzzle::UpdateFits
// UpdateFits commits tempFit to fit, after a swap is accepted
 void UpdateFits(Candidate* cd,int numCandidates) {
  for (int i=0;i<numCandidates;i++) {
   cd->fit=cd->tempFit;
   cd++;
  }
 }

Puzzle::Rearrange
// Rearrange shakes the puzzle a specified number of times
// and retains the configuration yielding the highest score
 void Rearrange(int howOften,Candidate* cd,int numCandidates) {
  for (int i=0;i<howOften;i++) {
   int s1,s2;
   unsigned long shakeProfile=RandomShake(s1,s2);
   if (Improves(shakeProfile,cd,numCandidates)) {
    UpdateFits(cd,numCandidates);
   } else {
    Swap(s1,s2);
   }    
  }
 }
Puzzle::Optimize
// Optimize calls Rearrange a number of times, to strike a
// compromise between points gained by random shakes, and
// points lost due to runtime cost.
 void Optimize(Candidate* cd,int numCandidates) {
  tmr.StartTimer();
  int run=kFirstRun;
  int countRuns=0;
  int runningRate;
  int oldPoints=points;
  int basePoints=points;
  Rearrange(run,cd,numCandidates);
  int runTime=tmr.ReadTimer();
  int lost=(runTime+kPenaltyRate/2)/kPenaltyRate;
  do {
   oldPoints=points;
   countRuns+=run;
   runningRate=runTime/countRuns;   
   int pointsToRisk=points/riskFactor-lost;
   int run=kPenaltyRate*pointsToRisk/runningRate;
   if (run<1) break;
   Rearrange(run,cd,numCandidates);
   runTime=tmr.ReadTimer();
   lost=(runTime+kPenaltyRate/2)/kPenaltyRate;
  } while (points > oldPoints);
 }

// The next set of functions relate to energy maximization

Puzzle::PrimePairs
// PrimePairs uses letter pairs in all candidate words
// to construct an array of basic energy values for each.
 void PrimePairs(Candidate* cd,int numCandidates) {
  memset(pairs,0,sizeof(pairs));
  for (int i=0;i<numCandidates;i++) {
   const char* wd=cd->word;
   int a=*wd & 31,b;
   do {
    b=*++wd & 31;
    if (b==0) break;
    pairs[32*a+b]=pairs[a+32*b]+=cd->value;
    a=b;
   } while(1);
   cd++;
  }
 }

Puzzle::InitEnergy
// Computes the energy of each puzzle field
 void InitEnergy() {
  for (int i=0;i<dimSquare;i++)
   energy[i]=GetEnergy(i);
 }

Puzzle::GetEnergy
// Get the energy for one field, using the Neighborhood
// struct to trace the field's neighbors.
 int GetEnergy(int k) {
  char** tour=N.nb[k].next;
  char* loc;
  int* pairP=pairs+32*(P[k]&31);
  int e=0;
  while (0 != (loc=*tour++)) {
   e+=pairP[*loc&31];
  }
  return e;
 }

Puzzle::CommitSwap
// This swap did some good, let's keep it
 void CommitSwap(int a,int b){
  Swap(a,b);
  energy[a]=GetEnergy(a);
  energy[b]=GetEnergy(b);
 }

Puzzle::ComputeDelta
// ComputeDelta makes a tentative swap and returns
// the increase or decrease in energy.
 int ComputeDelta(int a,int b) {
  if ((a==b)||(P[a]==P[b])) return 0;
  Swap(a,b);
  int ea=GetEnergy(a);
  int eb=GetEnergy(b);
  Swap(a,b);                        // restore previous state
  return ea+eb-energy[a]-energy[b];
 }

Puzzle::ComputeBestSwap
// ComputeBestSwap tries all possible swaps and returns
// the swap yielding the highest energy increase
 int ComputeBestSwap(int & aa,int & bb) {
  int bestDelta=-10000;
  for (int a=1;a<dimSquare;a++) {
   for (int b=0;b<a;b++) {
    if (P[a]^P[b]) {
     int delta=ComputeDelta(a,b);
     if (delta>bestDelta) {
      bestDelta=delta;aa=a;bb=b;
     }
    }
   }
  }
  return bestDelta;
 }

Puzzle::MaximizeEnergy
// MaximizeEnergy keeps swapping puzzle letters until no
// more increase in puzzle energy can be obtained.
 void MaximizeEnergy() {
  int a,b,delta=ComputeBestSwap(a,b);
  do {
   if (delta>0) CommitSwap(a,b);
   else break;
   delta=ComputeBestSwap(a,b);
  } while (1);
 }
};

PrivateData
struct PrivateData {   // just the puzzle and the candidate words
 Puzzle   pzl;
 int      numCandidates;
 Candidate   candidates[1];    // open ended array

 void Init(int dimension,char* puzzle) {
  pzl.Init(dimension,puzzle);
 }

 void SelectCandidates(int dictSize,const char *dictionary[]) {
  numCandidates=0;
  for (int i=0;i<dictSize;i++) {
   const char* word=dictionary[i];
   int len=pzl.IsPossible(word);
   if (len>=kMinLen)
    candidates[numCandidates++]=Candidate(len,word);
  }
  pzl.PrimePairs(candidates,numCandidates);
 }

 void Solve() {
  pzl.InitEnergy();
  pzl.MaximizeEnergy();      
  pzl.Evaluate(candidates,numCandidates);
  pzl.Optimize(candidates,numCandidates);
 }

 int CopyResults(const char *wordsFound[]) {
  int n=0;
  Candidate* cd=candidates;
  for (int i=0;i<numCandidates;i++) {
   wordsFound[n]=cd->word;
   n+=cd->fit;
   cd++;
  }   
  return n;
 }
};

Boggle
// the function Boggle is published in boggle.h
long Boggle(
   long dimension,   
   char puzzle[],   
   long dictSize,   
   const char *dictionary[],
   const char *wordsFound[],   
   void *privStorage   
   ) {   
   
 int nFound=0;
 srand(10001);   // just to make it repeatable

 if ((unsigned long)dimension <= kMaxDim) {
   PrivateData* PD=(PrivateData*)privStorage; // assumed to be enough
  PD->Init(dimension,puzzle);               
  PD->SelectCandidates(dictSize,dictionary);
  PD->Solve();
  nFound=PD->CopyResults(wordsFound);
 }

 return nFound;   
}