package flow

import (
	"bytes"
	"encoding/json"
	"errors"
	"flow/registry"
	"fmt"
	"io"
	"os"
	"sync"
)

// Data interface
type Data = interface{}

type opEntry struct {
	sync.Mutex
	name     string
	inputs   []*operation // still figuring, might be operation
	executor interface{}
}

// Flow structure
// We could Create a single array of operations
// refs would only mean id, types would be embed in operation
type Flow struct {
	sync.Mutex

	registry   *registry.R
	idGen      func() string
	consts     map[string]Data
	data       map[string]Data // Should be named, to fetch later
	operations sync.Map
	runID      int

	// Experimental run Event
	hooks Hooks
}

// New create a new flow
func New() *Flow {
	return &Flow{
		registry: registry.Global,
		idGen:    func() string { return RandString(8) },
		// Data
		consts:     map[string]Data{},
		data:       map[string]Data{},
		operations: sync.Map{},
		//map[string]opEntry{},
	}
}

//SetRegistry use the registry specified
func (f *Flow) SetRegistry(r *registry.R) *Flow {
	f.registry = r
	// chain
	return f
}

//SetIDGen set the id generator that will generate
//ID for new nodes
func (f *Flow) SetIDGen(idGen func() string) {
	f.idGen = idGen
}

// Must Helper to return from operations
func (f *Flow) Must(op Operation, err error) Operation {
	if err != nil {
		panic(err)
	}
	return op
}

// Res returns a deferred operation result
// passing the Id
func (f *Flow) Res(id string) Operation {
	return opFunc(f, id)
}

// DefOp Manual tag an Operation
func (f *Flow) DefOp(id string, name string, params ...interface{}) (Operation, error) {
	inputs := make([]*operation, len(params))
	for i, p := range params {
		switch v := p.(type) {
		case *operation:
			inputs[i] = v
		default:
			c, err := f.Const(v)
			if err != nil {
				return nil, err
			}
			inputs[i], _ = c.(*operation)
		}
	}
	// Grab executor here
	executor, err := f.registry.Get(name)
	if err != nil {
		return nil, err
	}
	f.operations.Store(id, &opEntry{sync.Mutex{}, name, inputs, executor})
	return opFunc(f, id), nil
}

// Op return an function operator
//  name - a previous registered function
//  params - the function inputs
func (f *Flow) Op(name string, params ...interface{}) (Operation, error) {
	var op Operation
	var err error

	allocErr := f.allocID(func(id string) error {
		op, err = f.DefOp(id, name, params...)
		return err
	})
	if allocErr != nil {
		return nil, allocErr
	}
	return op, err
}

// DefErrOp define a nil operation that will return error
// Usefull for builders
func (f *Flow) DefErrOp(id string, err error) (Operation, error) {
	executor := func() error { return err }
	f.operations.Store(id, &opEntry{sync.Mutex{}, fmt.Sprintf("(error)<%v>", err), nil, executor})
	return opFunc(f, id), nil
}

// ErrOp error operation with generated ID
func (f *Flow) ErrOp(operr error) (Operation, error) {
	var op Operation
	var err error

	allocErr := f.allocID(func(id string) error {
		op, err = f.DefErrOp(id, operr)
		return err
	})
	if allocErr != nil {
		return nil, err
	}
	return op, err
}

// DefConst define a const by defined ID
func (f *Flow) DefConst(id string, value Data) (Operation, error) {
	f.consts[id] = value
	executor := func() Data { return f.consts[id] }
	f.operations.Store(id, &opEntry{sync.Mutex{}, fmt.Sprintf("(const)<%s>", id), nil, executor})
	return opFunc(f, id), nil
}

// Const returns a const operation with generated ID
func (f *Flow) Const(value Data) (Operation, error) {
	var op Operation
	var err error
	allocErr := f.allocID(func(id string) error {
		op, err = f.DefConst(id, value)
		return err
	})
	if allocErr != nil {
		return nil, allocErr
	}
	return op, err
}

// Var operation
func (f *Flow) Var(name string, initial ...Data) Operation {
	if _, ok := f.data[name]; !ok {
		var v interface{}
		if len(initial) > 0 {
			v = initial[0]
		}
		f.data[name] = v
	}
	return opVar(f, name)
}

// In flow input operator
//  paramID - index of the parameter
func (f *Flow) In(paramID int) Operation {
	return opIn(f, paramID)
}

// Analyse every operations
func (f *Flow) Analyse(w io.Writer, params ...Data) {
	if w == nil {
		w = os.Stdout
	}
	fmt.Fprintf(w, "Ops analysis:\n")
	f.operations.Range(func(pk, po interface{}) bool {
		k, op := pk.(string), po.(*opEntry)
		fw := bytes.NewBuffer(nil)
		//fmt.Fprintf(w, "  [%s] (%v)", k, op.name)
		fmt.Fprintf(fw, "  [%s] %s(", pk, op.name)
		for j, in := range op.inputs {
			//ref := in.(Op)
			if j != 0 {
				fmt.Fprintf(fw, ", ")
			}
			ires, err := in.Process(params...)
			if err != nil {
				fmt.Fprintf(w, "Operator: %s error#%s\n", op.name, err)
				return false
			}
			fmt.Fprintf(fw, " %s[%v](%v)", in.kind, in.id, ires)
		}
		fmt.Fprintf(fw, ") - ")
		// Create OpProcessor and execute
		//
		opfn := opFunc(f, k)
		res, err := opfn.Process(params...)
		if err != nil {
			fmt.Fprintf(fw, "ERR\n")
		}
		fmt.Fprintf(fw, "%v\n", res)

		fmt.Fprintf(w, "%s", fw.String())
		return true
	})
}

/////////////////////////////
// Serializers inspectors
//////////////////////

func (f *Flow) String() string {
	ret := bytes.NewBuffer(nil)
	fmt.Fprintf(ret, "Flow\n")
	// consts
	fmt.Fprintf(ret, "consts:\n")
	for i, v := range f.consts {
		fmt.Fprintf(ret, "  [%s] %v\n", i, v)
	}
	fmt.Fprintf(ret, "data:\n") // Or variable
	for k, v := range f.data {
		fmt.Fprintf(ret, "  [%v] %v\n", k, v)
	}

	fmt.Fprintf(ret, "funcs:\n")
	f.operations.Range(func(pk, pv interface{}) bool {
		k, v := pk.(string), pv.(*opEntry)

		fmt.Fprintf(ret, "  [%s] %s(", k, v.name)
		for j, in := range v.inputs {
			if j != 0 {
				fmt.Fprintf(ret, ", ")
			}
			fmt.Fprintf(ret, "%s[%v]", in.kind, in.id)
		}
		fmt.Fprintf(ret, ")\n")
		return true
	})

	return ret.String()
}

// MarshalJSON implementation
func (f *Flow) MarshalJSON() ([]byte, error) {
	data := map[string]interface{}{}
	type opMarshal struct {
		Name  string
		Input []map[string]interface{}
	}
	operations := map[string]opMarshal{}
	f.operations.Range(func(pk, po interface{}) bool {
		k, o := pk.(string), po.(*opEntry)
		refs := []map[string]interface{}{}
		for _, in := range o.inputs { // Switch type?
			refs = append(refs, map[string]interface{}{
				"type": in.kind,
				"id":   in.id,
			})
		}
		operations[k] = opMarshal{o.name, refs}
		return true
	})

	data["operations"] = operations
	data["data"] = f.data
	data["consts"] = f.consts

	return json.Marshal(data)
}

func (f *Flow) allocID(fn func(id string) error) error {

	genID := func() (string, error) {
		f.Lock()
		defer f.Unlock()

		var id string
		// generate ID
		for i := 0; i < 10; i++ {
			id = f.idGen()
			if _, ok := f.operations.Load(id); !ok {
				f.operations.Store(id, nil) // tmp
				return id, nil
			}
		}
		return "", errors.New("ID Exausted")
	}

	// Safe generate an ID
	id, err := genID()
	if err != nil {
		return err
	}

	err = fn(id)
	if err != nil {
		f.operations.Delete(id)
	}
	return nil

}

func (f *Flow) addEntry(entry *opEntry) (string, error) {
	f.Lock()
	defer f.Unlock()

	// generate ID
	for i := 0; i < 10; i++ {
		id := f.idGen()
		if _, ok := f.operations.Load(id); ok {
			continue
		}
		f.operations.Store(id, entry)
		return id, nil
	}
	return "", errors.New("ID exausted")

}

/////////////////
// Async data
/////
func (f *Flow) getOp(id string) (*opEntry, bool) {

	o, ok := f.operations.Load(id)
	if !ok {
		return nil, false
	}
	return o.(*opEntry), true
}

// GetOp Return an existing operation or return notfound error
func (f *Flow) GetOp(id string) Operation {
	_, ok := f.operations.Load(id)
	if !ok {
		return nil
	}
	return opFunc(f, id)

}

//////////////////////////////////////////////
// Experimental event
////////////////

// Hook attach the node event hooks
func (f *Flow) Hook(hook Hook) {
	f.hooks.Attach(hook)
}