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

package parse

import (
	"errors"
	"fmt"
	"reflect"
	"strconv"

	"sectorinf.com/emilis/flabk/pkg/coll"
	"sectorinf.com/emilis/flabk/pkg/ld/internal/consts"
	"sectorinf.com/emilis/flabk/pkg/ld/internal/parse/chunk"
)

const (
	memberSeparator = ','
)

var (
	ErrNotArray = errors.New("value is not an array")
	ErrNotMap   = errors.New("value is not a map")
)

var (
	boolVals = map[string]bool{
		"true":  true,
		"false": false,
	}
	determineMap = func() map[byte]coll.Vector[reflect.Kind] {
		m := map[byte]coll.Vector[reflect.Kind]{
			'"': coll.From(reflect.String),
			'[': coll.From(reflect.Array, reflect.Slice),
			'{': coll.From(reflect.Map, reflect.Struct),
			'-': coll.From(reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64),
			't': coll.From(reflect.Bool),
			'f': coll.From(reflect.Bool),
		}
		numbers := coll.From(
			reflect.Int,
			reflect.Int8,
			reflect.Int16,
			reflect.Int32,
			reflect.Int64,
			reflect.Uint,
			reflect.Uint64,
			reflect.Uint32,
			reflect.Uint16,
			reflect.Uint8,
			reflect.Float32,
			reflect.Float64,
		)
		for index := byte('0'); index <= '9'; index++ {
			m[index] = numbers
		}

		return m
	}()
	sizes = map[reflect.Kind]int{
		// Int and Uint values stolen from the [math] package, as the intSize
		// constant is unexported
		reflect.Int:     32 << (^uint(0) >> 63), // 32 or 64
		reflect.Uint:    32 << (^uint(0) >> 63), // 32 or 64
		reflect.Int64:   64,
		reflect.Int32:   32,
		reflect.Int16:   16,
		reflect.Int8:    8,
		reflect.Uint64:  64,
		reflect.Uint32:  32,
		reflect.Uint16:  16,
		reflect.Uint8:   8,
		reflect.Float32: 32,
		reflect.Float64: 64,
	}
)

func SetMap(val reflect.Value, typ reflect.Type, c chunk.Chunk) error {
	if c.LeftByte() != '{' {
		return c.LeftPosf("%w", ErrNotMap)
	}
	fields := GetStructFields(val, typ)
	c = c.CookieCutter().Seek()
	for !c.EOF() {
		row, err := c.Row()
		if err != nil {
			return fmt.Errorf("row: %w", err)
		}
		field, ok := fields[row.Name]
		if ok {
			if err := SetValue(field, field.Type(), row.Value); err != nil {
				return fmt.Errorf("set: %w", err)
			}
		}

		// Shift c
		c = c.After(row.Value).StepIf(memberSeparator).Seek()
	}

	return nil
}

func SetArray(val reflect.Value, typ reflect.Type, c chunk.Chunk) error {
	if c.LeftByte() != '[' {
		return c.LeftPosf("%w", ErrNotArray)
	}

	c = c.CookieCutter().Seek()
	elems := coll.New[chunk.Chunk]()
	for !c.EOF() {
		element, err := c.ValueEnd()
		if err != nil {
			return fmt.Errorf("getting array elem: %w", err)
		}
		elems = elems.Push(element)
		c = c.After(element).StepIf(memberSeparator).Seek()
	}
	elementType := typ.Elem()
	arrayType := reflect.ArrayOf(len(elems), elementType)
	array := reflect.New(arrayType).Elem()
	for index, elem := range elems {
		if err := SetValue(array.Index(index), elementType, elem); err != nil {
			return fmt.Errorf("%w at array index [%d]", err, index)
		}
	}
	if val.Kind() == reflect.Slice {
		array = array.Slice(0, len(elems))
	}
	val.Set(array)
	return nil
}

// Determines what [reflect.Kind] of object the given [chunk.Chunk] is
func Determine(c chunk.Chunk) coll.Vector[reflect.Kind] {
	k, ok := determineMap[c.LeftByte()]
	if !ok {
		return coll.From(reflect.Invalid)
	}
	return k
}

func SetValue(val reflect.Value, typ reflect.Type, c chunk.Chunk) error {
	if c.Null() {
		return nil
	}

	if val.Kind() == reflect.Pointer {
		if val.IsNil() {
			val.Set(reflect.New(typ.Elem()))
		}
		return SetValue(val.Elem(), typ.Elem(), c)
	}

	kinds := Determine(c)
	if !coll.AnyOf(kinds, val.Kind()) {
		return fmt.Errorf("kind %s not found in appropriate list %s for value [%s]", val.Kind(), kinds, c)
	}

	switch val.Kind() {
	case reflect.Map, reflect.Struct:
		return SetMap(val, typ, c)
	case reflect.String:
		val.SetString(Escape(c.CookieCutter()))
	case reflect.Bool:
		b, ok := boolVals[c.String()]
		if !ok {
			return fmt.Errorf("value [%s] is not a boolean", c.String())
		}
		val.SetBool(b)
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		i, err := strconv.ParseInt(c.String(), 10, sizes[val.Kind()])
		if err != nil {
			return fmt.Errorf("value [%s] is not an %s", c.String(), val.Kind().String())
		}
		val.SetInt(i)
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		u, err := strconv.ParseUint(c.String(), 10, sizes[val.Kind()])
		if err != nil {
			return fmt.Errorf("value [%s] is not an %s", c.String(), val.Kind().String())
		}
		val.SetUint(u)
	case reflect.Float32, reflect.Float64:
		f, err := strconv.ParseFloat(c.String(), sizes[val.Kind()])
		if err != nil {
			return fmt.Errorf("value [%s] is not an %s", c.String(), val.Kind().String())
		}
		val.SetFloat(f)
	case reflect.Array, reflect.Slice:
		return SetArray(val, typ, c)
	default:
		fmt.Println(val.Kind().String())
		panic("unsupported")
	}

	return nil
}

func Escape(v chunk.Chunk) string {
	// TODO: string escaping
	return v.String()
}

func GetStructFields(val reflect.Value, typ reflect.Type) map[string]reflect.Value {
	total := val.NumField()
	out := map[string]reflect.Value{}
	for index := 0; index < total; index++ {
		cName := StructName(typ.Field(index))
		if cName != "-" {
			out[cName] = val.Field(index)
		}
	}
	return out
}

func StructName(v reflect.StructField) string {
	tag := v.Tag.Get(consts.PkgTag)
	if tag != "" {
		return tag
	}
	// Default to field name
	return v.Name
}