#include "engine.h"
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>

static bool spawn_process(const char *path, Engine *e){
    int inpipe[2], outpipe[2];
    if (pipe(inpipe)<0 || pipe(outpipe)<0) return false;
    pid_t pid = fork();
    if (pid < 0) return false;
    if (pid == 0){
        dup2(inpipe[0], STDIN_FILENO); // child stdin from inpipe[0]
        dup2(outpipe[1], STDOUT_FILENO); // child stdout to outpipe[1]
        dup2(outpipe[1], STDERR_FILENO);
        close(inpipe[0]); close(inpipe[1]); close(outpipe[0]); close(outpipe[1]);
        execlp(path, path, (char*)NULL);
        _exit(127);
    }
    // parent
    close(inpipe[0]); close(outpipe[1]);
    e->pid = pid; e->in_fd = inpipe[1]; e->out_fd = outpipe[0]; e->ready=false;
    // make out_fd non-blocking for reads with polling
    int flags = fcntl(e->out_fd, F_GETFL, 0); fcntl(e->out_fd, F_SETFL, flags | O_NONBLOCK);
    return true;
}

static bool try_start(Engine *e, const char *name){
    if (!spawn_process(name, e)) return false;
    // send UCI init
    engine_cmd(e, "uci\n");
    char buf[4096]; int attempts=50; // ~5s total
    while (attempts--){
        usleep(100000);
        ssize_t n = read(e->out_fd, buf, sizeof(buf)-1);
        if (n>0){
            buf[n]='\0';
            if (strstr(buf, "uciok")) { e->ready=true; break; }
        }
    }
    if (!e->ready){ engine_stop(e); return false; }
    engine_cmd(e, "isready\n");
    attempts=50;
    while (attempts--){
        usleep(100000);
        ssize_t n = read(e->out_fd, buf, sizeof(buf)-1);
        if (n>0){ buf[n]='\0'; if (strstr(buf, "readyok")) break; }
    }
    return e->ready;
}

bool engine_start(Engine *e){
    memset(e, 0, sizeof(*e)); e->pid=-1; e->in_fd=-1; e->out_fd=-1; e->ready=false;
    if (try_start(e, "stockfish")) return true;
    if (try_start(e, "asmfish")) return true;
    return false;
}

void engine_stop(Engine *e){
    if (e->in_fd!=-1){ write(e->in_fd, "quit\n", 5); close(e->in_fd); }
    if (e->out_fd!=-1) close(e->out_fd);
    if (e->pid>0){ int status; waitpid(e->pid, &status, 0); }
    e->pid=-1; e->in_fd=e->out_fd=-1; e->ready=false;
}

bool engine_cmd(Engine *e, const char *cmd){
    if (e->in_fd==-1) return false;
    size_t len = strlen(cmd);
    ssize_t n = write(e->in_fd, cmd, len);
    if (n < 0) {
        return false;
    }
    return n == (ssize_t)len;
}

static void position_to_uci(const Position *pos, char *out, size_t outsz){
    // Send starting position and moves list by comparing with startpos; for simplicity, use FEN always.
    char fen[256]; chess_to_fen(pos, fen, sizeof(fen));
    snprintf(out, outsz, "position fen %s\n", fen);
}

size_t engine_get_top_moves(Engine *e, const Position *pos, EngineMove *out, size_t max){
    if (!e->ready) return 0;
    char cmd[512]; position_to_uci(pos, cmd, sizeof(cmd)); engine_cmd(e, cmd);
    // ask multiPV up to max (cap at 5 as requested)
    size_t req = max; if (req>5) req=5; char go[128]; snprintf(go, sizeof(go), "setoption name MultiPV value %zu\n", req); engine_cmd(e, go);
    engine_cmd(e, "go movetime 400\n");
    char buf[8192]; size_t count=0; int attempts=50;
    while (attempts--){
        usleep(100000);
    ssize_t n = read(e->out_fd, buf, sizeof(buf)-1);
    if (n<=0) continue;
    buf[n]='\0';
        char *line = strtok(buf, "\n");
        while (line){
            if (strncmp(line, "info ", 5)==0){
                // parse "info ... multipv X score cp Y ... pv <uci>"
                char *mpv = strstr(line, " multipv "); char *score = strstr(line, " score "); char *pv = strstr(line, " pv ");
                if (mpv && score && pv){
                    int idx = atoi(mpv+9); if (idx>=1 && (size_t)idx<=req){
                        int cp=0; if (strstr(score, "cp ")) cp = atoi(strstr(score, "cp ")+3);
                        char mv[8]={0};
                        sscanf(pv+4, "%7s", mv);
                        size_t i = (size_t)idx-1; if (i<req){ out[i].score_cp = cp; snprintf(out[i].uci, sizeof(out[i].uci), "%s", mv); if (i+1>count) count=i+1; }
                    }
                }
            } else if (strncmp(line, "bestmove ", 9)==0){ attempts=0; break; }
            line = strtok(NULL, "\n");
        }
    }
    // simple sort by score descending (best to worst), keeping empties at end
    for (size_t i=0;i<count;i++){
        for (size_t j=i+1;j<count;j++){
            if (out[j].score_cp > out[i].score_cp){ EngineMove tmp=out[i]; out[i]=out[j]; out[j]=tmp; }
        }
    }
    return count;
}

bool engine_get_best_move(Engine *e, const Position *pos, char out_uci[8]){
    if (!e->ready) return false;
    char cmd[512]; position_to_uci(pos, cmd, sizeof(cmd)); engine_cmd(e, cmd);
    engine_cmd(e, "go movetime 300\n");
    char buf[4096]; int attempts=50;
    while (attempts--){
        usleep(100000);
    ssize_t n = read(e->out_fd, buf, sizeof(buf)-1);
    if (n<=0) continue;
    buf[n]='\0';
        char *line = strtok(buf, "\n");
        while (line){
            if (strncmp(line, "bestmove ", 9)==0){ sscanf(line+9, "%7s", out_uci); return true; }
            line = strtok(NULL, "\n");
        }
    }
    return false;
}