flabk/pkg/ld/internal/parse/chunk/chunk.go

package chunk

import (
	"errors"
	"fmt"
	"unicode"
	"unicode/utf8"

	"sectorinf.com/emilis/flabk/pkg/coll"
)

var (
	ErrNoMatch            = errors.New("no matching")
	ErrMapMemberNotString = errors.New("map member not a string")
	ErrUnexpectedSymbol   = errors.New("unexpected symbol")
)

type Chunk struct {
	vector   coll.Vector[byte]
	posLeft  int
	posRight int
	// todo global pos impl
	globLeft  int
	globRight int
}

// Match finds the matching closer to the symbol at the left position and sets the
// right position to this index
func (c Chunk) Match() (Chunk, error) {
	s, ok := matchers[c.vector[c.posLeft]]
	if !ok {
		panic(fmt.Sprintf("Match called on %c with no matcher defined", c.vector[c.posLeft]))
	}
	if s.StartFromRight {
		for c.posRight > 0 {
			if c.vector[c.posRight] == s.MatchByte {
				return c, nil
			}
			c.posRight--
			c.globRight--
		}
	} else {
		for index := c.posLeft + 1; index < len(c.vector); index++ {
			if c.vector[index] == s.MatchByte {
				c.posRight = index
				c.globRight += (c.posLeft + 1) - index
				return c, nil
			}
		}
	}

	return c, fmt.Errorf("%w %c", ErrNoMatch, c.vector[c.posLeft])
}

func (c Chunk) Copy() Chunk {
	return c
}

func (c Chunk) Left() byte {
	return c.vector[c.posLeft]
}

// Sub returns an inclusive subchunk of [left;right]
func (c Chunk) Sub() Chunk {
	return New(c.vector[c.posLeft : c.posRight+1])
}

// CookieCutter returns a subchunk of (left;right)
func (c Chunk) CookieCutter() Chunk {
	return New(c.vector[c.posLeft+1 : c.posRight])
}

func (c Chunk) AtSpace() bool {
	r, _ := utf8.DecodeRune(c.vector[c.posLeft:])
	return unicode.IsSpace(r)
}

func (c Chunk) Seek() Chunk {
	for c.posLeft < len(c.vector) && c.AtSpace() {
		c.posLeft++
	}
	return c
}

func (c Chunk) ValueEnd() (Chunk, error) {
	switch c.vector[c.posLeft] {
	case '"', '{', '[':
		return c.Match()
	default:
		for index := c.posLeft; index <= c.posRight; index++ {
			if c.vector[index] == ',' {
				return New(c.vector[c.posLeft:index]), nil
			}
		}
		return c, nil
	}
}

// Skip skips the current left position and then Seeks
func (c Chunk) Skip() Chunk {
	if c.posLeft+1 < len(c.vector) {
		c.posLeft++
	}
	return c.Seek()
}

type MatchRule struct {
	MatchByte      byte
	StartFromRight bool
}

var (
	matchers = map[byte]MatchRule{
		'{': {
			MatchByte:      '}',
			StartFromRight: true,
		},
		'[': {
			MatchByte:      ']',
			StartFromRight: true,
		},
		'"': {
			MatchByte: '"',
		},
	}
)

func New(v []byte) Chunk {
	posRight := len(v) - 1
	if len(v) == 0 {
		posRight = 0
	}
	return Chunk{
		vector:   coll.Vector[byte](v),
		posLeft:  0,
		posRight: posRight,
	}
}

func (c Chunk) Child(left, right int) Chunk {
	sub := c.vector[left:right]
	return Chunk{
		vector:    sub,
		posLeft:   0,
		posRight:  len(sub),
		globLeft:  (c.globLeft - c.posLeft) + left,
		globRight: (c.globRight - c.posRight) + right,
	}
}

type ParseFunc[T any] func(T) (T, error)

func Parse[T any](c Chunk) ParseFunc[T] {
	switch c.vector[c.posLeft] {
	case '{':
		return ParseMap[T](c.CookieCutter())
	default:
		panic("not implemented")
	}
	// return can be:
	// * {}
	// * []
	// * ""
	// * 123
	// * true
	// * false
	// * null
}

type Row struct {
	Name  string
	Value Chunk
}

func (c Chunk) String() string {
	return string(c.vector[c.posLeft : c.posRight+1])
}

func (c Chunk) Row() (Row, error) {
	c = c.Seek()
	if c.vector[c.posLeft] != '"' {
		return Row{}, fmt.Errorf("%w: %c", ErrMapMemberNotString, c.vector[c.posLeft])
	}
	name, err := c.Match()
	if err != nil {
		return Row{}, fmt.Errorf("match: %w", err)
	}
	postName := c.Copy()
	postName.posLeft = name.posRight
	postName = postName.Skip()
	// Next we must get a :
	if postName.vector[postName.posLeft] != ':' {
		return Row{}, fmt.Errorf("%w '%c', expected ':'", ErrUnexpectedSymbol, postName.vector[postName.posLeft])
	}
	value, err := postName.Skip().ValueEnd()
	if err != nil {
		return Row{}, fmt.Errorf("value: %w", err)
	}

	return Row{
		Name:  name.String(),
		Value: value,
	}, nil
}

func (c Chunk) After(v Chunk) Chunk {
	c.posLeft = v.posLeft
	return c
}

func ParseMap[T any](c Chunk) ParseFunc[T] {
	return func(t T) (T, error) {
		// mapper := parse.GetMap(t)
		// for {
		// 	row, err := c.Row()
		// 	if err != nil {
		// 		return t, err
		// 	}

		// }
		panic("todo")
	}
}