package chain

import (
	"encoding"
	"fmt"

	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/marshal"
)

const (
	ChainMarshalVersion uint8 = 0 // increase if breaking change
)

var (
	_ encoding.BinaryMarshaler   = (*Chain)(nil)
	_ encoding.BinaryUnmarshaler = (*Chain)(nil)
)

func (c *Chain) MarshalBinary() ([]byte, error) {
	s := marshal.UInt8Size // Marshaller version
	s += marshal.UInt8Size // Chain version
	s += marshal.StringSize(string(c.ID))
	s += marshal.SliceSize(c.Rules, ruleSize)
	s += marshal.UInt8Size // MatchType

	buf := make([]byte, s)
	var offset int
	var err error
	offset, err = marshal.UInt8Marshal(buf, offset, marshal.Version)
	if err != nil {
		return nil, err
	}
	offset, err = marshal.UInt8Marshal(buf, offset, ChainMarshalVersion)
	if err != nil {
		return nil, err
	}
	offset, err = marshal.StringMarshal(buf, offset, string(c.ID))
	if err != nil {
		return nil, err
	}
	offset, err = marshal.SliceMarshal(buf, offset, c.Rules, marshalRule)
	if err != nil {
		return nil, err
	}
	offset, err = marshal.UInt8Marshal(buf, offset, uint8(c.MatchType))
	if err != nil {
		return nil, err
	}

	if err := marshal.VerifyMarshal(buf, offset); err != nil {
		return nil, err
	}
	return buf, nil
}

func (c *Chain) UnmarshalBinary(data []byte) error {
	var offset int

	marshallerVersion, offset, err := marshal.UInt8Unmarshal(data, offset)
	if err != nil {
		return err
	}
	if marshallerVersion != marshal.Version {
		return fmt.Errorf("unsupported marshaller version %d", marshallerVersion)
	}

	chainVersion, offset, err := marshal.UInt8Unmarshal(data, offset)
	if err != nil {
		return err
	}
	if chainVersion != ChainMarshalVersion {
		return fmt.Errorf("unsupported chain version %d", chainVersion)
	}

	idStr, offset, err := marshal.StringUnmarshal(data, offset)
	if err != nil {
		return err
	}
	c.ID = ID(idStr)

	c.Rules, offset, err = marshal.SliceUnmarshal(data, offset, unmarshalRule)
	if err != nil {
		return err
	}

	matchTypeV, offset, err := marshal.UInt8Unmarshal(data, offset)
	if err != nil {
		return err
	}
	c.MatchType = MatchType(matchTypeV)

	return marshal.VerifyUnmarshal(data, offset)
}

func ruleSize(r Rule) int {
	s := marshal.ByteSize // Status
	s += actionsSize(r.Actions)
	s += resourcesSize(r.Resources)
	s += marshal.BoolSize // Any
	s += marshal.SliceSize(r.Condition, conditionSize)
	return s
}

func marshalRule(buf []byte, offset int, r Rule) (int, error) {
	offset, err := marshal.ByteMarshal(buf, offset, byte(r.Status))
	if err != nil {
		return 0, err
	}
	offset, err = marshalActions(buf, offset, r.Actions)
	if err != nil {
		return 0, err
	}
	offset, err = marshalResources(buf, offset, r.Resources)
	if err != nil {
		return 0, err
	}
	offset, err = marshal.BoolMarshal(buf, offset, r.Any)
	if err != nil {
		return 0, err
	}
	return marshal.SliceMarshal(buf, offset, r.Condition, marshalCondition)
}

func unmarshalRule(buf []byte, offset int) (Rule, int, error) {
	var r Rule
	statusV, offset, err := marshal.ByteUnmarshal(buf, offset)
	if err != nil {
		return Rule{}, 0, err
	}
	r.Status = Status(statusV)

	r.Actions, offset, err = unmarshalActions(buf, offset)
	if err != nil {
		return Rule{}, 0, err
	}

	r.Resources, offset, err = unmarshalResources(buf, offset)
	if err != nil {
		return Rule{}, 0, err
	}

	r.Any, offset, err = marshal.BoolUnmarshal(buf, offset)
	if err != nil {
		return Rule{}, 0, err
	}

	r.Condition, offset, err = marshal.SliceUnmarshal(buf, offset, unmarshalCondition)
	if err != nil {
		return Rule{}, 0, err
	}

	return r, offset, nil
}

func actionsSize(a Actions) int {
	return marshal.BoolSize + // Inverted
		marshal.SliceSize(a.Names, marshal.StringSize)
}

func marshalActions(buf []byte, offset int, a Actions) (int, error) {
	offset, err := marshal.BoolMarshal(buf, offset, a.Inverted)
	if err != nil {
		return 0, err
	}
	return marshal.SliceMarshal(buf, offset, a.Names, marshal.StringMarshal)
}

func unmarshalActions(buf []byte, offset int) (Actions, int, error) {
	var a Actions
	var err error
	a.Inverted, offset, err = marshal.BoolUnmarshal(buf, offset)
	if err != nil {
		return Actions{}, 0, err
	}
	a.Names, offset, err = marshal.SliceUnmarshal(buf, offset, marshal.StringUnmarshal)
	if err != nil {
		return Actions{}, 0, err
	}
	return a, offset, nil
}

func resourcesSize(r Resources) int {
	return marshal.BoolSize + // Inverted
		marshal.SliceSize(r.Names, marshal.StringSize)
}

func marshalResources(buf []byte, offset int, r Resources) (int, error) {
	offset, err := marshal.BoolMarshal(buf, offset, r.Inverted)
	if err != nil {
		return 0, err
	}
	return marshal.SliceMarshal(buf, offset, r.Names, marshal.StringMarshal)
}

func unmarshalResources(buf []byte, offset int) (Resources, int, error) {
	var r Resources
	var err error
	r.Inverted, offset, err = marshal.BoolUnmarshal(buf, offset)
	if err != nil {
		return Resources{}, 0, err
	}
	r.Names, offset, err = marshal.SliceUnmarshal(buf, offset, marshal.StringUnmarshal)
	if err != nil {
		return Resources{}, 0, err
	}
	return r, offset, nil
}

func conditionSize(c Condition) int {
	return marshal.ByteSize + // Op
		marshal.ByteSize + // Object
		marshal.StringSize(c.Key) +
		marshal.StringSize(c.Value)
}

func marshalCondition(buf []byte, offset int, c Condition) (int, error) {
	offset, err := marshal.ByteMarshal(buf, offset, byte(c.Op))
	if err != nil {
		return 0, err
	}
	offset, err = marshal.ByteMarshal(buf, offset, byte(c.Object))
	if err != nil {
		return 0, err
	}
	offset, err = marshal.StringMarshal(buf, offset, c.Key)
	if err != nil {
		return 0, err
	}
	return marshal.StringMarshal(buf, offset, c.Value)
}

func unmarshalCondition(buf []byte, offset int) (Condition, int, error) {
	var c Condition
	opV, offset, err := marshal.ByteUnmarshal(buf, offset)
	if err != nil {
		return Condition{}, 0, err
	}
	c.Op = ConditionType(opV)

	obV, offset, err := marshal.ByteUnmarshal(buf, offset)
	if err != nil {
		return Condition{}, 0, err
	}
	c.Object = ObjectType(obV)

	c.Key, offset, err = marshal.StringUnmarshal(buf, offset)
	if err != nil {
		return Condition{}, 0, err
	}

	c.Value, offset, err = marshal.StringUnmarshal(buf, offset)
	if err != nil {
		return Condition{}, 0, err
	}

	return c, offset, nil
}