go-vise

db.go (15495B)

---

 package engine
 
 import (
 	"bytes"
 	"context"
 	"errors"
 	"fmt"
 	"io"
 	"os"
 
 	"git.defalsify.org/vise.git/cache"
 	"git.defalsify.org/vise.git/persist"
 	"git.defalsify.org/vise.git/render"
 	"git.defalsify.org/vise.git/resource"
 	"git.defalsify.org/vise.git/state"
 	"git.defalsify.org/vise.git/vm"
 )
 
 var (
 	ErrFlushNoExec = errors.New("Attempted flush on unexecuted engine")
 )
 
 type DefaultEngine struct {
 	st         *state.State
 	ca         cache.Memory
 	vm         *vm.Vm
 	rs         resource.Resource
 	pe         *persist.Persister
 	cfg        Config
 	dbg        Debug
 	first      resource.EntryFunc
 	initd      bool
 	exit       string
 	exiting    bool
 	execd      bool
 	regexCount int
 }
 
 // NewEngine instantiates the default Engine implementation.
 func NewEngine(cfg Config, rs resource.Resource) *DefaultEngine {
 	if rs == nil {
 		panic("resource cannot be nil")
 	}
 	en := &DefaultEngine{
 		rs:  rs,
 		cfg: cfg,
 	}
 	if en.cfg.Root == "" {
 		en.cfg.Root = "root"
 	}
 	return en
 }
 
 // WithState is a chainable method that explicitly sets the state object to use for the engine.
 //
 // If not set, the state.State object provided by the persist.Persister will be used.
 // If that is not available, a new instance will be created according to engine.Config.
 //
 // Note that engine.Init will fail if state is set both explicitly
 // and in a provided persist.Persister.
 func (en *DefaultEngine) WithState(st *state.State) *DefaultEngine {
 	if en.st != nil {
 		panic("state already set")
 	}
 	if st == nil {
 		panic("state argument is nil")
 	}
 	en.st = st
 	return en
 }
 
 // WithMemory is a chainable method that explicitly sets the memory object to use for the engine.
 //
 // If not set, the cache.Memory object provided by the persist.Persister will be used.
 // If that is not available, a new instance will be created according to engine.Config.
 //
 // Note that engine.Init will fail if memory is set both explicitly
 // and in a provided persist.Persister.
 func (en *DefaultEngine) WithMemory(ca cache.Memory) *DefaultEngine {
 	if en.ca != nil {
 		panic("cache already set")
 	}
 	if ca == nil {
 		panic("cache argument is nil")
 	}
 	en.ca = ca
 	return en
 }
 
 // WithPersister is a chainable method that sets the persister to use with the engine.
 //
 // If the persister is missing state, memory or both, it will inherit them from the engine.
 func (en *DefaultEngine) WithPersister(pe *persist.Persister) *DefaultEngine {
 	if en.pe != nil {
 		panic("persister already set")
 	}
 	if pe == nil {
 		panic("persister argument is nil")
 	}
 	en.pe = pe
 	return en
 }
 
 // WithDebug is a chainable method that sets the debugger to use for the engine.
 //
 // If the argument is nil, the default debugger will be used.
 func (en *DefaultEngine) WithDebug(dbg Debug) *DefaultEngine {
 	if en.dbg != nil {
 		panic("debugger already set")
 	}
 	if dbg == nil {
 		logg.Infof("debug argument was nil, using default debugger")
 		dbg = NewSimpleDebug(os.Stderr)
 	}
 	en.dbg = dbg
 	return en
 }
 
 // WithFirst is a chainable method that defines the function that will be run before
 // control is handed over to the VM bytecode from the current state.
 //
 // If this function returns an error, execution will be aborted in engine.Init.
 func (en *DefaultEngine) WithFirst(fn resource.EntryFunc) *DefaultEngine {
 	if en.first != nil {
 		panic("firstfunc already set")
 	}
 	if fn == nil {
 		panic("firstfunc argument is nil")
 	}
 	en.first = fn
 	return en
 }
 
 // AddValidInput defines a regular expressing string to match input against.
 //
 // The added regular expression will be evaluated after the builtin match (see
 // vm/input.go for the actual string details).
 //
 // The function may be called more than once. Input will be validated against each
 // in the sequence they were added.
 //
 // When a match is found, remaining regular expressions will be skipped.
 func (en *DefaultEngine) AddValidInput(re string) error {
 	err := vm.RegisterInputValidator(en.regexCount, re)
 	en.regexCount += 1
 	return err
 }
 
 // ensure state is present in engine.
 func (en *DefaultEngine) ensureState() {
 	if en.st == nil {
 		st := state.NewState(en.cfg.FlagCount)
 		en.st = st
 		en.st.SetLanguage(en.cfg.Language)
 		if en.st.Language != nil {
 			en.st.SetFlag(state.FLAG_LANG)
 		}
 		logg.Debugf("new engine state added", "state", en.st)
 	} else {
 		if en.cfg.Language != "" {
 			if en.st.Language == nil {
 				en.st.SetLanguage(en.cfg.Language)
 				en.st.SetFlag(state.FLAG_LANG)
 			} else {
 				logg.Warnf("language '%s'set in config, but will be ignored because state language has already been set.")
 			}
 		}
 	}
 }
 
 // ensure memory is present in engine.
 func (en *DefaultEngine) ensureMemory() error {
 	cac, ok := en.ca.(*cache.Cache)
 	if cac == nil {
 		ca := cache.NewCache()
 		if en.cfg.CacheSize > 0 {
 			ca = ca.WithCacheSize(en.cfg.CacheSize)
 		}
 		en.ca = ca
 		logg.Debugf("new engine memory added", "memory", en.ca)
 	} else if !ok {
 		return errors.New("memory MUST be *cache.Cache for now. sorry")
 	}
 
 	return nil
 }
 
 // retrieve state and memory from perister if present.
 func (en *DefaultEngine) preparePersist() error {
 	if en.pe == nil {
 		return nil
 	}
 	st := en.pe.GetState()
 	if st != nil {
 		if en.st != nil {
 			return errors.New("state cannot be explicitly set in both persister and engine.")
 		}
 		en.st = st
 	} else {
 		if en.st == nil {
 			logg.Debugf("defer persist state set until state set in engine")
 		}
 	}
 
 	ca := en.pe.GetMemory()
 	cac, ok := ca.(*cache.Cache)
 	if !ok {
 		return errors.New("memory MUST be *cache.Cache for now. sorry")
 	}
 	if cac != nil {
 		logg.Debugf("ca", "ca", cac)
 		if en.ca != nil {
 			return errors.New("cache cannot be explicitly set in both persister and engine.")
 		}
 		en.ca = cac
 	} else {
 		if en.ca == nil {
 			logg.Debugf("defer persist memory set until memory set in engine")
 		}
 	}
 	return nil
 }
 
 // synchronize state and memory between engine and persister.
 func (en *DefaultEngine) ensurePersist() error {
 	if en.pe == nil {
 		return nil
 	}
 	st := en.pe.GetState()
 	if st == nil {
 		st = en.st
 		logg.Debugf("using engine state for persister", "state", st)
 	} else {
 		en.st = st
 	}
 	ca := en.pe.GetMemory()
 	cac, ok := ca.(*cache.Cache)
 	if cac == nil {
 		cac, ok = en.ca.(*cache.Cache)
 		if !ok {
 			return errors.New("memory MUST be *cache.Cache for now. sorry")
 		}
 		logg.Debugf("using engine memory for persister", "memory", cac)
 	} else {
 		en.ca = cac
 	}
 	en.pe = en.pe.WithContent(st, cac)
 	err := en.pe.Load(en.cfg.SessionId)
 	if err != nil {
 		logg.Infof("persister load fail. trying save in case new session", "err", err, "session", en.cfg.SessionId)
 		err = en.pe.Save(en.cfg.SessionId)
 		if err != nil {
 			return err
 		}
 		en.pe = en.pe.WithContent(st, cac)
 		err = en.pe.Load(en.cfg.SessionId)
 	}
 	if en.cfg.StateDebug {
 		en.st.UseDebug()
 	}
 	logg.Tracef("set persister", "st", st, "cac", cac, "session", en.cfg.SessionId, "persister", en.pe)
 	return err
 }
 
 // create vm instance.
 func (en *DefaultEngine) setupVm() {
 	var szr *render.Sizer
 	if en.cfg.OutputSize > 0 {
 		szr = render.NewSizer(en.cfg.OutputSize)
 	}
 	en.vm = vm.NewVm(en.st, en.rs, en.ca, szr)
 	if en.cfg.MenuSeparator != "" {
 		en.vm = en.vm.WithMenuSeparator(en.cfg.MenuSeparator)
 	}
 }
 
 func (en *DefaultEngine) empty(ctx context.Context) error {
 	var err error
 	b := bytes.NewBuffer(nil)
 	_, err = en.Flush(ctx, b)
 	if err != nil {
 		return err
 	}
 	logg.DebugCtxf(ctx, "discard", "output", b.Bytes())
 	return nil
 }
 
 // prepare engine for Init run.
 func (en *DefaultEngine) prepare(ctx context.Context) error {
 	if en.execd {
 		err := en.empty(ctx)
 		if err != nil {
 			return err
 		}
 	}
 	en.execd = false
 	en.exit = ""
 	en.exiting = false
 	if en.initd {
 		return nil
 	}
 	err := en.preparePersist()
 	if err != nil {
 		return err
 	}
 	en.ensureState()
 	err = en.ensureMemory()
 	if err != nil {
 		return err
 	}
 	err = en.ensurePersist()
 	if err != nil {
 		return err
 	}
 	en.setupVm()
 	return nil
 }
 
 // execute the first function, if set.
 func (en *DefaultEngine) runFirst(ctx context.Context) (bool, error) {
 	var err error
 	var r bool
 	if en.first == nil {
 		return true, nil
 	}
 	logg.DebugCtxf(ctx, "start pre-VM check")
 	en.ca.Push()
 	rs := resource.NewMenuResource()
 	rs.AddLocalFunc("_first", en.first)
 	en.st.Down("_first")
 	defer en.ca.Pop()
 	defer en.st.Up()
 	defer en.st.ResetFlag(state.FLAG_TERMINATE)
 	defer en.st.ResetFlag(state.FLAG_DIRTY)
 	pvm := vm.NewVm(en.st, rs, en.ca, nil)
 	b := vm.NewLine(nil, vm.LOAD, []string{"_first"}, []byte{0}, nil)
 	b = vm.NewLine(b, vm.HALT, nil, nil, nil)
 	b, err = pvm.Run(ctx, b)
 	if err != nil {
 		return false, err
 	}
 	if len(b) > 0 {
 		// TODO: typed error
 		err = fmt.Errorf("Pre-VM code cannot have remaining bytecode after execution, had: %x", b)
 	} else {
 		if en.st.MatchFlag(state.FLAG_TERMINATE, true) {
 			en.execd = true
 			en.exit = en.ca.Last()
 			logg.InfoCtxf(ctx, "Pre-VM check says not to continue execution", "state", en.st)
 		} else {
 			r = true
 		}
 	}
 	if err != nil {
 		en.st.Invalidate()
 		en.ca.Invalidate()
 	}
 	logg.DebugCtxf(ctx, "end pre-VM check")
 	return r, err
 }
 
 // Finish implements the Engine interface.
 //
 // If persister is set, this call will save the state and memory.
 //
 // An error will be logged and returned if:
 //   - persistence was attempted and failed (takes precedence)
 //   - resource backend did not close cleanly.
 func (en *DefaultEngine) Finish(ctx context.Context) error {
 	var perr error
 	if !en.initd {
 		return nil
 	}
 	if en.pe != nil {
 		perr = en.pe.Save(en.cfg.SessionId)
 	}
 	err := en.rs.Close(ctx)
 	if err != nil {
 		logg.Errorf("resource close failed!", "err", err)
 	}
 	if perr != nil {
 		logg.Errorf("persistence failed!", "err", perr)
 		err = perr
 	}
 	if err == nil {
 		logg.Tracef("that's a wrap", "engine", en)
 	}
 	return err
 }
 
 func (en *DefaultEngine) setCode(ctx context.Context, code []byte) (bool, error) {
 	var err error
 
 	cont := true
 	en.st.SetCode(code)
 	if len(code) == 0 {
 		logg.InfoCtxf(ctx, "runner finished with no remaining code", "state", en.st)
 		if en.st.MatchFlag(state.FLAG_DIRTY, true) {
 			logg.Debugf("have output for quitting")
 			en.exiting = true
 			en.exit = en.ca.Last()
 		}
 		cont = false
 	}
 	return cont, err
 }
 
 // Init implements the Engine interface.
 //
 // It loads and executes code for the start node.
 func (en *DefaultEngine) init(ctx context.Context, input []byte) (bool, error) {
 	cont := true
 	err := en.prepare(ctx)
 	if err != nil {
 		return false, err
 	}
 
 	if en.st.Language != nil {
 		logg.TraceCtxf(ctx, "set language on context", "lang", en.st.Language)
 		ctx = context.WithValue(ctx, "Language", *en.st.Language)
 	}
 
 	if en.initd {
 		logg.DebugCtxf(ctx, "already initialized")
 		return true, nil
 	}
 
 	sym := en.cfg.Root
 	if sym == "" {
 		return false, fmt.Errorf("start sym empty")
 	}
 
 	inSave, _ := en.st.GetInput()
 	err = en.st.SetInput(input)
 	if err != nil {
 		return false, err
 	}
 
 	r, err := en.runFirst(ctx)
 	if err != nil {
 		return false, err
 	}
 	if !r {
 		return false, nil
 	}
 
 	if len(en.st.Code) == 0 {
 		b := vm.NewLine(nil, vm.MOVE, []string{sym}, nil, nil)
 		cont, err = en.setCode(ctx, b)
 		if err != nil {
 			return false, err
 		}
 	}
 
 	err = en.st.SetInput(inSave)
 	if err != nil {
 		return false, err
 	}
 	en.initd = true
 	return cont, nil
 }
 
 // Exec implements the Engine interface.
 //
 // It processes user input against the current state of the virtual machine environment.
 //
 // If successfully executed, output of the last execution is available using the Flush call.
 //
 // A bool return valus of false indicates that execution should be terminated. Calling Exec again has undefined effects.
 //
 // Fails if:
 //   - input is formally invalid (too long etc)
 //   - no current bytecode is available
 //   - input processing against bytcode failed
 func (en *DefaultEngine) Exec(ctx context.Context, input []byte) (bool, error) {
 	var err error
 
 	if en.cfg.SessionId != "" {
 		ctx = context.WithValue(ctx, "SessionId", en.cfg.SessionId)
 	}
 
 	cont, err := en.init(ctx, input)
 	if err != nil {
 		return false, err
 	}
 	if !cont {
 		return cont, nil
 	}
 
 	if en.st.Language != nil {
 		ctx = context.WithValue(ctx, "Language", *en.st.Language)
 	}
 
 	if en.cfg.ResetOnEmptyInput {
 		if len(input) == 0 {
 			v, err := en.Reset(ctx, true)
 			if err != nil {
 				return v, err
 			}
 		}
 	}
 
 	if len(input) > 0 {
 		_, err = vm.ValidInput(input)
 		if err != nil {
 			return true, err
 		}
 	}
 	err = en.st.SetInput(input)
 	if err != nil {
 		return false, err
 	}
 	return en.exec(ctx, input)
 }
 
 // backend for Exec, after the input validity check
 func (en *DefaultEngine) exec(ctx context.Context, input []byte) (bool, error) {
 	logg.InfoCtxf(ctx, "new VM execution with input", "input", input)
 	code, err := en.st.GetCode()
 	if err != nil {
 		return false, err
 	}
 	if len(code) == 0 {
 		return false, fmt.Errorf("no code to execute")
 	}
 
 	logg.Debugf("start new VM run", "code", code)
 	code, err = en.vm.Run(ctx, code)
 	if err != nil {
 		return false, err
 	}
 	en.execd = true
 	logg.Debugf("end new VM run", "code", code)
 
 	v := en.st.MatchFlag(state.FLAG_TERMINATE, true)
 	if v {
 		if len(code) > 0 {
 			logg.Debugf("terminated with code remaining", "code", code)
 		}
 		return false, err
 	}
 	cont, err := en.setCode(ctx, code)
 	if en.dbg != nil {
 		en.dbg.Break(en.st, en.ca)
 	}
 	return cont, err
 }
 
 // Flush implements the Engine interface.
 //
 // The method writes the output of the last vm execution to the given writer.
 //
 // Fails if
 //   - required data inputs to the template are not available.
 //   - the template for the given node point is note available for retrieval using the resource.Resource implementer.
 //   - the supplied writer fails to process the writes.
 func (en *DefaultEngine) Flush(ctx context.Context, w io.Writer) (int, error) {
 	var l int
 	if !en.execd {
 		return 0, ErrFlushNoExec
 	}
 	if en.st.Language != nil {
 		ctx = context.WithValue(ctx, "Language", *en.st.Language)
 	}
 	logg.TraceCtxf(ctx, "render with state", "state", en.st)
 	r, err := en.vm.Render(ctx)
 	if err != nil {
 		if len(en.exit) == 0 {
 			return 0, err
 		}
 	} else {
 		if len(r) > 0 {
 			l, err = io.WriteString(w, r)
 			if err != nil {
 				return l, err
 			}
 		}
 	}
 	if len(en.exit) > 0 {
 		logg.TraceCtxf(ctx, "have exit", "exit", en.exit)
 		n, err := io.WriteString(w, en.exit)
 		if err != nil {
 			return l, err
 		}
 		l += n
 	}
 	if en.exiting {
 		_, err = en.reset(ctx)
 		en.exiting = false
 	}
 
 	return l, err
 }
 
 // start execution over at top node while keeping current state of client error flags.
 func (en *DefaultEngine) Reset(ctx context.Context, force bool) (bool, error) {
 	if en.st.Depth() == -1 {
 		logg.TraceCtxf(ctx, "reset on pristine state is a noop")
 		return false, nil
 	}
 	if en.st == nil {
 		return false, fmt.Errorf("reset on engine with nil state")
 	}
 	if force {
 		sym := en.cfg.Root
 		if sym == "" {
 			return false, fmt.Errorf("start sym empty")
 		}
 		b := vm.NewLine(nil, vm.MOVE, []string{sym}, nil, nil)
 		en.st.SetCode(b)
 	} else {
 		b, err := en.st.GetCode()
 		if err != nil {
 			return false, err
 		}
 		if len(b) > 0 {
 			return false, ErrCodeRemaining
 		}
 	}
 	return en.reset(ctx)
 }
 
 func (en *DefaultEngine) reset(ctx context.Context) (bool, error) {
 	var err error
 	var isTop bool
 	logg.DebugCtxf(ctx, "entering engine reset", "state", en.st)
 	for !isTop {
 		isTop, err = en.st.Top()
 		if err != nil {
 			return false, err
 		}
 		_, err = en.st.Up()
 		if err != nil {
 			return false, err
 		}
 		en.ca.Pop()
 	}
 	en.st.Restart()
 	en.st.ResetFlag(state.FLAG_TERMINATE)
 	en.st.ResetFlag(state.FLAG_DIRTY)
 	return false, nil
 }