fq/pkg/decode/value.go

package decode

import (
	"errors"
	"sort"

	"github.com/wader/fq/pkg/bitio"
	"github.com/wader/fq/pkg/ranges"
)

type DisplayFormat int

const (
	NumberDecimal DisplayFormat = iota
	NumberBinary
	NumberOctal
	NumberHex
)

func DisplayFormatToBase(fmt DisplayFormat) int {
	switch fmt {
	case NumberDecimal:
		return 10
	case NumberBinary:
		return 2
	case NumberOctal:
		return 8
	case NumberHex:
		return 16
	default:
		return 0
	}
}

type Struct []*Value

type Array []*Value

// TODO: encoding? endian, string encoding, compression, etc?
type Value struct {
	Parent        *Value
	V             interface{} // int, int64, uint64, float64, string, bool, []byte, *bitio.Buffer, Array, Struct
	Index         int         // index in parent array/struct
	Range         ranges.Range
	RootBitBuf    *bitio.Buffer
	IsRoot        bool
	Name          string
	DisplayFormat DisplayFormat
	Symbol        string
	Description   string
	Format        *Format
	Unknown       bool
	Err           error
}

type WalkFn func(v *Value, rootV *Value, depth int, rootDepth int) error

var ErrWalkSkipChildren = errors.New("skip children")
var ErrWalkBreak = errors.New("break")
var ErrWalkStop = errors.New("stop")

func (v *Value) walk(preOrder bool, fn WalkFn) error {
	var walkFn WalkFn
	walkFn = func(v *Value, rootV *Value, depth int, rootDepth int) error {
		rootDepthDelta := 0
		if v.IsRoot {
			rootV = v
			rootDepthDelta = 1
		}

		if preOrder {
			err := fn(v, rootV, depth, rootDepth+rootDepthDelta)
			switch {
			case errors.Is(err, ErrWalkSkipChildren):
				return nil
			case errors.Is(err, ErrWalkStop):
				fallthrough
			default:
				if err != nil {
					return err
				}
			}
		}

		switch v := v.V.(type) {
		case Struct:
			for _, wv := range v {
				if err := walkFn(wv, rootV, depth+1, rootDepth+rootDepthDelta); err != nil {
					if errors.Is(err, ErrWalkBreak) {
						break
					}
					return err
				}
			}
		case Array:
			for _, wv := range v {
				if err := walkFn(wv, rootV, depth+1, rootDepth+rootDepthDelta); err != nil {
					if errors.Is(err, ErrWalkBreak) {
						break
					}
					return err
				}
			}
		}
		if !preOrder {
			err := fn(v, rootV, depth, rootDepth+rootDepthDelta)
			switch {
			case errors.Is(err, ErrWalkSkipChildren):
				return errors.New("can't skip children in post-order")
			case errors.Is(err, ErrWalkStop):
				fallthrough
			default:
				if err != nil {
					return err
				}
			}
		}
		return nil
	}

	// figure out root value for v as it might not be a root itself
	rootV := v.BufferRoot()

	err := walkFn(v, rootV, 0, 0)
	if errors.Is(err, ErrWalkStop) {
		err = nil
	}

	return err
}

func (v *Value) root(findSubRoot bool, findFormatRoot bool) *Value {
	rootV := v
	for rootV.Parent != nil {
		if findSubRoot && rootV.IsRoot {
			break
		}
		if findFormatRoot && rootV.Format != nil {
			break
		}

		rootV = rootV.Parent
	}
	return rootV
}

func (v *Value) Root() *Value       { return v.root(false, false) }
func (v *Value) BufferRoot() *Value { return v.root(true, false) }
func (v *Value) FormatRoot() *Value { return v.root(true, true) }

func (v *Value) WalkPreOrder(fn WalkFn) error {
	return v.walk(true, fn)
}

func (v *Value) WalkPostOrder(fn WalkFn) error {
	return v.walk(false, fn)
}

func (v *Value) Errors() []error {
	var errs []error
	_ = v.WalkPreOrder(func(v *Value, rootV *Value, depth int, rootDepth int) error {
		if v.Err != nil {
			errs = append(errs, v.Err)
		}
		return nil
	})
	return errs
}

func (v *Value) postProcess() {
	if err := v.WalkPostOrder(func(v *Value, rootV *Value, depth int, rootDepth int) error {
		switch vv := v.V.(type) {
		case Struct:
			first := true
			for _, f := range vv {
				if f.IsRoot {
					continue
				}

				if first {
					v.Range = f.Range
					first = false
				} else {
					v.Range = ranges.MinMax(v.Range, f.Range)
				}
			}

			sort.Slice(vv, func(i, j int) bool {
				return vv[i].Range.Start < vv[j].Range.Start
			})

			for i, f := range vv {
				f.Index = i
			}
		case Array:
			first := true
			for _, f := range vv {
				if f.IsRoot {
					continue
				}

				if first {
					v.Range = f.Range
					first = false
				} else {
					v.Range = ranges.MinMax(v.Range, f.Range)
				}
			}

			for i, f := range vv {
				f.Index = i
			}

			// TODO: also sort?
		}
		return nil
	}); err != nil {
		panic(err)
	}
}