package host

import (
	"context"
	"crypto/sha256"
	"debug/buildinfo"
	"encoding/hex"
	"io"
	"os"

	"github.com/carlosframework/platform/internal/hostbox"
	"github.com/carlosframework/platform/internal/instancectl"
	"github.com/carlosframework/platform/internal/rootstate"
	"github.com/carlosframework/platform/internal/safefile"
)

func (h *ClaimLaunchRoot) rootInstalledProgram(ctx context.Context, q hostbox.RoleLaunchRequest, started instancectl.ClaimUnitStarted, observed ClaimLaunchObserved) (string, error) {
	if q.Reservation == nil || q.Spec == nil || observed.TenantPID <= 0 || observed.TenantStart == "" || observed.Running != q.Reservation.Executable || observed.Executable != observed.Running {
		return "", os.ErrPermission
	}
	if err := h.ValidateExecutable(q.Reservation.Target.Host, q.Executable, q.Spec.Digest); err != nil {
		return "", err
	}
	f, err := safefile.OpenFile(q.Executable, os.O_RDONLY, 0)
	if err != nil {
		return "", err
	}
	defer f.Close()
	id, err := rootstate.Identity(f)
	if err != nil {
		return "", err
	}
	if id.Device != observed.Running.Device || id.Inode != observed.Running.Inode {
		return "", os.ErrPermission
	}
	digest := sha256.New()
	if _, err := io.Copy(digest, f); err != nil {
		return "", err
	}
	if hex.EncodeToString(digest.Sum(nil)) != q.Spec.Digest {
		return "", os.ErrPermission
	}
	program := ""
	if info, err := buildinfo.Read(f); err == nil {
		program = info.Path
	}
	again, err := h.Kernel.Observe(started)
	if err != nil || again != observed {
		return "", os.ErrPermission
	}
	if err := h.Units.Same(ctx, started); err != nil {
		return "", err
	}
	return program, nil
}