package compatibility

import (
	"errors"
	"strings"

	"github.com/hashicorp/go-version"
)

var (
	// ErrStaticVersionRequired error returned when the static version is not provided.
	ErrStaticVersionRequired = errors.New("static version is required")
	// ErrActualVersionRequired error returned when the actual version is not provided.
	ErrActualVersionRequired = errors.New("expected version is required")
	// ErrStaticVersionCannotBeSHA error returned when the static version provided is a sha256.
	ErrStaticVersionCannotBeSHA = errors.New("static version cannot be a sha256")
	// ErrActualVersionCannotBeSHA error returned when the actual version provided is a sha256.
	ErrActualVersionCannotBeSHA = errors.New("expected version cannot be a sha256")
)

// Compare compares the static version against the expected version using the specified operation.
// Examples:
// Latest -> EQUAL -> Latest = true
// Latest -> EQUAL -> 0.20 = false
// Latest -> GreaterThan -> 0.20 = true
// 0.20 -> LessThan -> 0.21 = true
func Compare(op Operation, staticVersion, expectedVersion string) (bool, error) { //nolint
	if staticVersion == "" {
		return false, ErrStaticVersionRequired
	}
	if expectedVersion == "" {
		return false, ErrActualVersionRequired
	}
	if strings.HasPrefix(staticVersion, "sha256:") {
		return false, ErrStaticVersionCannotBeSHA
	}
	if strings.HasPrefix(expectedVersion, "sha256:") {
		return false, ErrActualVersionCannotBeSHA
	}
	var (
		staticVerifiedVersion *version.Version
		fleetVersion          *version.Version
		err                   error
	)
	if staticVersion != Latest {
		staticVerifiedVersion, err = version.NewVersion(staticVersion)
		if err != nil {
			return false, err
		}
	}
	if expectedVersion != Latest {
		fleetVersion, err = version.NewVersion(expectedVersion)
		if err != nil {
			return false, err
		}
	}
	switch op {
	case Equal:
		if staticVersion == Latest && expectedVersion == Latest {
			return true, nil
		}
		if (staticVersion != Latest && expectedVersion == Latest) || (staticVersion == Latest && expectedVersion != Latest) {
			return false, nil
		}
		return staticVerifiedVersion.Equal(fleetVersion), nil
	case LessThan:
		if staticVersion == Latest && expectedVersion != Latest {
			return false, nil
		}
		if staticVersion != Latest && expectedVersion == Latest {
			return true, nil
		}
		if staticVersion == Latest && expectedVersion == Latest {
			return false, nil
		}
		return staticVerifiedVersion.LessThan(fleetVersion), nil
	case GreaterThan:
		if staticVersion == Latest && expectedVersion != Latest {
			return true, nil
		}
		if staticVersion != Latest && expectedVersion == Latest {
			return false, nil
		}
		if staticVersion == Latest && expectedVersion == Latest {
			return false, nil
		}
		return staticVerifiedVersion.GreaterThan(fleetVersion), nil
	case LessThanOrEqual:
		if staticVersion == Latest && expectedVersion != Latest {
			return false, nil
		}
		if staticVersion == Latest && expectedVersion == Latest {
			return true, nil
		}
		if staticVersion != Latest && expectedVersion == Latest {
			return true, nil
		}
		return staticVerifiedVersion.LessThanOrEqual(fleetVersion), nil
	case GreaterThanOrEqual:
		if staticVersion == Latest && expectedVersion != Latest {
			return true, nil
		}
		if staticVersion == Latest && expectedVersion == Latest {
			return true, nil
		}
		if staticVersion != Latest && expectedVersion == Latest {
			return false, nil
		}
		return staticVerifiedVersion.GreaterThanOrEqual(fleetVersion), nil
	default:
		return false, nil
	}
}