micro/fsm/fsm.go
Vasiliy Tolstov c7da7d5bc8 fsm: initial import
Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>
2022-04-15 15:20:17 +03:00

152 lines
3.1 KiB
Go

package fsm // import "go.unistack.org/micro/v3/fsm"
import (
"context"
"errors"
"fmt"
"sync"
)
var (
ErrInvalidState = errors.New("does not exists")
StateEnd = "end"
)
// Options struct holding fsm options
type Options struct {
// Initial state
Initial string
// HooksBefore func slice runs in order before state
HooksBefore []HookBeforeFunc
// HooksAfter func slice runs in order after state
HooksAfter []HookAfterFunc
}
// HookBeforeFunc func signature
type HookBeforeFunc func(ctx context.Context, state string, args map[string]interface{})
// HookAfterFunc func signature
type HookAfterFunc func(ctx context.Context, state string, args map[string]interface{})
// Option func signature
type Option func(*Options)
// StateInitial sets init state for state machine
func StateInitial(initial string) Option {
return func(o *Options) {
o.Initial = initial
}
}
// StateHookBefore provides hook func slice
func StateHookBefore(fns ...HookBeforeFunc) Option {
return func(o *Options) {
o.HooksBefore = fns
}
}
// StateHookAfter provides hook func slice
func StateHookAfter(fns ...HookAfterFunc) Option {
return func(o *Options) {
o.HooksAfter = fns
}
}
// StateFunc called on state transition and return next step and error
type StateFunc func(ctx context.Context, args map[string]interface{}) (string, map[string]interface{}, error)
// FSM is a finite state machine
type FSM struct {
mu sync.Mutex
states map[string]StateFunc
opts *Options
current string
}
// New creates a new finite state machine having the specified initial state
// with specified options
func New(opts ...Option) *FSM {
options := &Options{}
for _, opt := range opts {
opt(options)
}
return &FSM{
states: map[string]StateFunc{},
opts: options,
}
}
// Current returns the current state
func (f *FSM) Current() string {
f.mu.Lock()
defer f.mu.Unlock()
return f.current
}
// Current returns the current state
func (f *FSM) Reset() {
f.mu.Lock()
f.current = f.opts.Initial
f.mu.Unlock()
}
// State adds state to fsm
func (f *FSM) State(state string, fn StateFunc) {
f.mu.Lock()
f.states[state] = fn
f.mu.Unlock()
}
// Start runs state machine with provided data
func (f *FSM) Start(ctx context.Context, args map[string]interface{}, opts ...Option) (map[string]interface{}, error) {
var err error
var ok bool
var fn StateFunc
var nstate string
f.mu.Lock()
options := f.opts
for _, opt := range opts {
opt(options)
}
cstate := options.Initial
states := make(map[string]StateFunc, len(f.states))
for k, v := range f.states {
states[k] = v
}
f.current = cstate
f.mu.Unlock()
for {
select {
case <-ctx.Done():
return nil, ctx.Err()
default:
fn, ok = states[cstate]
if !ok {
return nil, fmt.Errorf(`state "%s" %w`, cstate, ErrInvalidState)
}
f.mu.Lock()
f.current = cstate
f.mu.Unlock()
for _, fn := range options.HooksBefore {
fn(ctx, cstate, args)
}
nstate, args, err = fn(ctx, args)
for _, fn := range options.HooksAfter {
fn(ctx, cstate, args)
}
if err != nil {
return args, err
} else if nstate == "" || nstate == StateEnd {
return args, nil
}
cstate = nstate
}
}
}