package monitor

import (
    "execguard/core/alert"
    "execguard/core/configure"
    "execguard/core/sys_database"
    "database/sql"
	"golang.org/x/sys/unix"
    "path/filepath"
    "encoding/binary"
    "sync"
    "fmt"
    "log"
    "os"
    "bytes"
    "time"
    "unsafe"
)

const sizeofFanotifyEventMetadata = int(unsafe.Sizeof(unix.FanotifyEventMetadata{}))

var (
    config configure.Config
    initMode bool
    initFile string
    updateFile string
    migrateMode bool
    dbMutex sync.Mutex
    alertCache sync.Map
)

func SetModes(mode bool, file string, update string, migrate bool) {
    initMode = mode
    initFile = file
    updateFile = update
    migrateMode = migrate    
}

func SetGlobalConfig(c configure.Config) {
    config = c
}

func MonitorExecutions(db *sql.DB, log log.Logger, mailPath string) error {
    fd, err := unix.FanotifyInit(unix.FAN_CLOEXEC|unix.FAN_CLASS_CONTENT, unix.O_RDONLY|unix.O_LARGEFILE)
    if err != nil {
        return fmt.Errorf("fanotify init failed: %w", err)
    }
    defer unix.Close(fd)

    success := false
    for _, dir := range config.ProtectedDirs {
        if err := unix.FanotifyMark(fd, unix.FAN_MARK_ADD|unix.FAN_MARK_MOUNT, unix.FAN_OPEN_EXEC_PERM, unix.AT_FDCWD, dir); err != nil {
            log.Printf("Failed to mark %s: %v", dir, err)
        } else {
            success = true
        }
    }
    if !success {
        return fmt.Errorf("failed to mark any protected directories")
    }

    buf := make([]byte, 4096)

    defer func() {
        if r := recover(); r != nil {
            log.Printf("Recovered from panic in monitorExecutions: %v", r)
        }
    }()

    for {
        n, err := unix.Read(fd, buf)
        if err != nil {
            return fmt.Errorf("fanotify read failed: %w", err)
        }

        for offset := 0; offset < n; {
            if n-offset < sizeofFanotifyEventMetadata {
                break
            }

            meta := (*unix.FanotifyEventMetadata)(unsafe.Pointer(&buf[offset]))
            if meta.Event_len == 0 {
                break
            }

            resp := unix.FanotifyResponse{Fd: meta.Fd, Response: unix.FAN_ALLOW}
            shouldClose := true

            if meta.Mask&unix.FAN_OPEN_EXEC_PERM != 0 {
                fdpath := fmt.Sprintf("/proc/self/fd/%d", meta.Fd)
                path, err := os.Readlink(fdpath)
                if err == nil {
                    absPath, _ := filepath.Abs(path)
                    absPath, _ = filepath.EvalSymlinks(absPath)
                    if info, statErr := os.Stat(absPath); statErr == nil &&
                        info.Mode().IsRegular() && (info.Mode().Perm()&0111 != 0) {

                        if initMode {
                            go func(p string, fd int) {
                                sys_database.AddToAllowed(db, log, p)
                                unix.Close(fd)
                            }(absPath, int(meta.Fd))
                            shouldClose = false
                        } else {
                            if !sys_database.IsAllowed(db, log, absPath) {
                                log.Printf("Blocked execution attempt: %s", absPath)

                                if _, seen := alertCache.LoadOrStore(absPath, struct{}{}); !seen {
                                    go alert.SendAlert(fmt.Sprintf("Unauthorized execution attempt blocked: %s", absPath), db, log)
                                    time.AfterFunc(10*time.Minute, func() {
                                        alertCache.Delete(absPath)
                                    })
                                }

                                resp.Response = unix.FAN_DENY
                            }
                        }
                    }
                }
            }

            var respBuf bytes.Buffer
            if err := binary.Write(&respBuf, binary.LittleEndian, resp); err != nil {
                log.Printf("Failed to encode fanotify response: %v", err)
            } else if _, err := unix.Write(fd, respBuf.Bytes()); err != nil {
                log.Printf("Fanotify response write error: %v", err)
            }

            if shouldClose {
                unix.Close(int(meta.Fd))
            }

            offset += int(meta.Event_len)
        }
    }
}