package instruction

import (
	"fmt"
	"github.com/xdrm-brackets/nix-amer/internal/exec"
	"github.com/xdrm-brackets/nix-amer/internal/pkg"
	"github.com/xdrm-brackets/nix-amer/internal/ser"
)

// T is the instruction common interface
type T interface {
	// Raw input line
	Raw() string
	// Build the instruction with input arguments
	Build(string) error
	// Exec the given instruction
	Exec(ExecutionContext) ([]byte, error)
	// DryRun checks the success of the given instruction without actually running it (non-destructive)
	DryRun(ExecutionContext) ([]byte, error)
}

// ExecutionContext contains system-specific drivers to manage the host
type ExecutionContext struct {
	PackageManager pkg.PackageManager
	ServiceManager ser.ServiceManager
	Executor       exec.Executor
	Alias          map[string]string
}

// CreateContext creates an execution contet with the given package-manager and service-manager
// default values are taken from each go package (pkg, ser)
// if _exec is set, it will override the default (os) executor
func CreateContext(_pkg, _ser string, _exec ...exec.Executor) (*ExecutionContext, error) {

	// 1. fail if no value and no defaults
	if len(_pkg)+len(pkg.DefaultManager) < 1 {
		return nil, fmt.Errorf("missing package manager")
	}
	if len(_ser)+len(ser.DefaultManager) < 1 {
		return nil, fmt.Errorf("missing service manager")
	}

	// 2. set default
	if len(_pkg) < 1 {
		_pkg = pkg.DefaultManager
	}
	if len(_ser) < 1 {
		_ser = ser.DefaultManager
	}

	var executor exec.Executor = new(exec.Default)

	// 3. load custom executor (optional)
	if len(_exec) > 0 && _exec[0] != nil {
		executor = _exec[0]
	}

	// 4. load managers
	pkg, err := pkg.Load(_pkg, executor)
	if err != nil {
		return nil, fmt.Errorf("package manager: %s", err)
	}
	ser, err := ser.Load(_ser, executor)
	if err != nil {
		return nil, fmt.Errorf("service manager: %s", err)
	}

	// 4. build context
	return &ExecutionContext{
		PackageManager: pkg,
		ServiceManager: ser,
		Executor:       executor,
		Alias:          make(map[string]string),
	}, nil

}