package runtime

import (
	"path"
	"strings"

	"git.sendico.io/tech/sxchnge/product/app/api"
	"git.sendico.io/tech/sxchnge/shared/errors"
)

func validMount(value string) bool {
	if value == "" || value == "/" || !strings.HasPrefix(value, "/") || path.Clean(value) != value {
		return false
	}
	for _, c := range value {
		if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || strings.ContainsRune("/-._~", c) {
			continue
		}
		return false
	}
	return true
}
func overlaps(a, b string) bool {
	return a == b || strings.HasPrefix(a, b+"/") || strings.HasPrefix(b, a+"/")
}

func resolveMounts(configured []api.Mount, endpoint string, supported map[string]api.Installer) ([]api.Mount, error) {
	if !validMount(endpoint) {
		return nil, merrors.InvalidArgument("a canonical absolute API endpoint is required", "api_endpoint")
	}
	if configured == nil {
		configured = []api.Mount{{Version: "v1", Path: endpoint}}
	}
	seen := map[string]bool{}
	for i, mount := range configured {
		if supported[mount.Version] == nil {
			return nil, merrors.InvalidArgument("unknown or unavailable API version: "+mount.Version, "api.versions")
		}
		if seen[mount.Version] {
			return nil, merrors.InvalidArgument("duplicate API version: "+mount.Version, "api.versions")
		}
		seen[mount.Version] = true
		if !validMount(mount.Path) {
			return nil, merrors.InvalidArgument("invalid API mount: "+mount.Path, "api.versions")
		}
		for _, reserved := range []string{"/metrics", endpoint + "/metrics", endpoint + "/health"} {
			if mount.Path == reserved || strings.HasPrefix(mount.Path, reserved+"/") {
				return nil, merrors.InvalidArgument("API mount conflicts with operational endpoint", "api.versions")
			}
		}
		for _, previous := range configured[:i] {
			if overlaps(mount.Path, previous.Path) {
				return nil, merrors.InvalidArgument("overlapping API mounts", "api.versions")
			}
		}
	}
	return configured, nil
}