package wmo

import (
	"context"
	"go.mongodb.org/mongo-driver/bson/bsontype"
	"go.mongodb.org/mongo-driver/mongo"
	ct "gogs.mikescher.com/BlackForestBytes/goext/cursortoken"
	"gogs.mikescher.com/BlackForestBytes/goext/exerr"
	"gogs.mikescher.com/BlackForestBytes/goext/langext"
	"reflect"
)

type EntityID interface {
	MarshalBSONValue() (bsontype.Type, []byte, error)
	String() string
}

type Decodable interface {
	Decode(v any) error
}

type Cursorable interface {
	Decode(v any) error
	Err() error
	Close(ctx context.Context) error
	All(ctx context.Context, results any) error
	RemainingBatchLength() int
	Next(ctx context.Context) bool
}

type fullTypeRef struct {
	IsPointer      bool
	Kind           reflect.Kind
	RealType       reflect.Type
	Type           reflect.Type
	UnderlyingType reflect.Type
	Name           string
	Index          []int
}

type IColl interface {
	Collection() *mongo.Collection
	Name() string
	Indexes() mongo.IndexView
	Drop(ctx context.Context) error
}

type Coll[TData any] struct {
	coll                *mongo.Collection                                        // internal mongo collection, access via Collection()
	dataTypeMap         map[string]fullTypeRef                                   // list of TData fields (only if TData is not an interface)
	implDataTypeMap     map[reflect.Type]map[string]fullTypeRef                  // dynamic list of fields of TData implementations (only if TData is an interface)
	customDecoder       *func(ctx context.Context, dec Decodable) (TData, error) // custom decoding function (useful if TData is an interface)
	isInterfaceDataType bool                                                     // true if TData is an interface (not a struct)
	unmarshalHooks      []func(d TData) TData                                    // called for every object after unmarshalling
	marshalHooks        []func(d TData) TData                                    // called for every object before marshalling
	extraModPipeline    []func(ctx context.Context) mongo.Pipeline               // appended to pipelines after filter/limit/skip/sort, used for $lookup, $set, $unset, $project, etc
}

func (c *Coll[TData]) Collection() *mongo.Collection {
	return c.coll
}

func (c *Coll[TData]) Name() string {
	return c.coll.Name()
}

func (c *Coll[TData]) Indexes() mongo.IndexView {
	return c.coll.Indexes()
}

func (c *Coll[TData]) Drop(ctx context.Context) error {
	err := c.coll.Drop(ctx)
	if err != nil {
		return exerr.Wrap(err, "failed to drop collection").Str("collection", c.Name()).Build()
	}
	return nil
}

func (c *Coll[TData]) WithDecodeFunc(cdf func(ctx context.Context, dec Decodable) (TData, error), example TData) *Coll[TData] {

	c.EnsureInitializedReflection(example)

	c.customDecoder = langext.Ptr(cdf)
	return c
}

// WithUnmarshalHook
// function that is called for every object after reading from DB
func (c *Coll[TData]) WithUnmarshalHook(fn func(d TData) TData) *Coll[TData] {
	c.unmarshalHooks = append(c.unmarshalHooks, fn)

	return c
}

// WithMarshalHook
// function that is called for every object before writing to DB
func (c *Coll[TData]) WithMarshalHook(fn func(d TData) TData) *Coll[TData] {
	c.marshalHooks = append(c.marshalHooks, fn)

	return c
}

// WithModifyingPipeline
// pipeline that is appended to all read operations (after filtering)
func (c *Coll[TData]) WithModifyingPipeline(p mongo.Pipeline) *Coll[TData] {
	c.extraModPipeline = append(c.extraModPipeline, func(ctx context.Context) mongo.Pipeline { return p })

	return c
}

// WithModifyingPipelineFunc
// pipeline that is appended to all read operations (after filtering)
func (c *Coll[TData]) WithModifyingPipelineFunc(fn func(ctx context.Context) mongo.Pipeline) *Coll[TData] {
	c.extraModPipeline = append(c.extraModPipeline, fn)

	return c
}

func (c *Coll[TData]) createToken(fieldPrimary string, dirPrimary ct.SortDirection, fieldSecondary *string, dirSecondary *ct.SortDirection, lastEntity TData, pageSize *int) (ct.CursorToken, error) {

	valuePrimary, err := c.getFieldValueAsTokenString(lastEntity, fieldPrimary)
	if err != nil {
		return ct.CursorToken{}, exerr.Wrap(err, "failed to get (primary) field-value as token-string").Type("lastEntity", lastEntity).Str("fieldPrimary", fieldPrimary).Build()
	}

	valueSeconary := ""
	if fieldSecondary != nil && dirSecondary != nil {
		valueSeconary, err = c.getFieldValueAsTokenString(lastEntity, *fieldSecondary)
		if err != nil {
			return ct.CursorToken{}, exerr.Wrap(err, "failed to get (secondary) field-value as token-string").Type("lastEntity", lastEntity).StrPtr("fieldSecondary", fieldSecondary).Build()
		}
	}

	return ct.CursorToken{
		Mode:           ct.CTMNormal,
		ValuePrimary:   valuePrimary,
		ValueSecondary: valueSeconary,
		Direction:      dirPrimary,
		PageSize:       langext.Coalesce(pageSize, 0),
		Extra:          ct.Extra{},
	}, nil
}

func (c *Coll[TData]) needsDoubleSort(ctx context.Context) bool {
	for _, ppl := range c.extraModPipeline {
		for _, stage := range ppl(ctx) {
			for _, bsone := range stage {
				if bsone.Key == "$group" {
					// a group stage in extraModPipeline results in unsorted data, which means the caller must sort again after these pipeline stages...
					return true
				}
			}
		}
	}
	return false
}