package taskassignment

import (
	"errors"
	"fmt"
	"slices"
)

type WorkloadClass string

const (
	WorkloadContainer WorkloadClass = "container"
	WorkloadVM        WorkloadClass = "vm"
)

type Driver string

const (
	DriverKubernetes  Driver = "kubernetes"
	DriverOpenSandbox Driver = "opensandbox"
)

type Placement struct {
	Class  WorkloadClass `json:"workload_class"`
	Driver Driver        `json:"driver"`
}

var (
	KubernetesContainer = Placement{Class: WorkloadContainer, Driver: DriverKubernetes}
	OpenSandboxVM       = Placement{Class: WorkloadVM, Driver: DriverOpenSandbox}
)

func (p Placement) Validate() error {
	switch p {
	case KubernetesContainer, OpenSandboxVM:
		return nil
	default:
		return fmt.Errorf("unsupported workload placement %s/%s", p.Class, p.Driver)
	}
}

func (p Placement) Key() string { return string(p.Class) + "." + string(p.Driver) }

func PlacementFromLabels(labels []string) (Placement, error) {
	if !slices.Contains(labels, "self-hosted") {
		return Placement{}, fmt.Errorf("task runs-on labels must include self-hosted: %v", labels)
	}
	legacyPod := slices.Contains(labels, "pod")
	container := slices.Contains(labels, string(WorkloadContainer))
	vm := slices.Contains(labels, string(WorkloadVM)) || slices.Contains(labels, "vm-dev")
	kubernetes := slices.Contains(labels, string(DriverKubernetes))
	opensandbox := slices.Contains(labels, string(DriverOpenSandbox))

	if legacyPod {
		if container || vm || kubernetes || opensandbox {
			return Placement{}, errors.New("legacy pod label cannot be combined with workload or VM driver labels")
		}
		return KubernetesContainer, nil
	}
	if container == vm {
		return Placement{}, fmt.Errorf("task runs-on labels must select exactly one workload class: %v", labels)
	}
	if kubernetes && opensandbox {
		return Placement{}, fmt.Errorf("task runs-on labels select multiple drivers: %v", labels)
	}
	if container {
		if opensandbox {
			return Placement{}, fmt.Errorf("opensandbox does not support container workloads")
		}
		return KubernetesContainer, nil
	}
	if kubernetes {
		return Placement{}, fmt.Errorf("kubernetes does not support VM workloads")
	}
	return OpenSandboxVM, nil
}