package glm

import (
	"errors"
	"fmt"
	"io/fs"
	"isle/daemon/daecommon"
	"os"
)

// targetAllocs is expected to have already been validated to be internally
// consistent, ie on conflicts between ports or directories within itself.
func validateTargetAllocs(
	activeAllocs, targetAllocs []daecommon.ConfigStorageAllocation,
) error {
	for _, targetAlloc := range targetAllocs {

		var alreadyActive bool
		for _, activeAlloc := range activeAllocs {
			switch {
			case targetAlloc.RPCPort == activeAlloc.RPCPort &&
				targetAlloc.DataPath == activeAlloc.DataPath &&
				targetAlloc.MetaPath == activeAlloc.MetaPath:
				alreadyActive = true
				break

			// Changing the value of all fields besides these is supported.
			case targetAlloc.RPCPort == activeAlloc.RPCPort:
				return fmt.Errorf(
					"RPC port %d is already being used", activeAlloc.RPCPort,
				)

			case targetAlloc.DataPath == activeAlloc.DataPath:
				return fmt.Errorf(
					"Data path %q is already being used", activeAlloc.DataPath,
				)

			case targetAlloc.MetaPath == activeAlloc.MetaPath:
				return fmt.Errorf(
					"Meta path %q is already being used", activeAlloc.MetaPath,
				)
			}
		}

		if !alreadyActive {
			for _, dir := range []string{
				targetAlloc.DataPath, targetAlloc.MetaPath,
			} {
				entries, err := os.ReadDir(dir)
				if errors.Is(err, fs.ErrNotExist) {
					continue
				} else if err != nil {
					return fmt.Errorf("reading contents of %q: %w", dir, err)
				}

				if len(entries) > 0 {
					return fmt.Errorf(
						"directory %q is already being used, please provide the path to an empty directory",
						dir,
					)
				}
			}
		}

		// targetAlloc validated
	}

	return nil
}