package loader

import (
	"encoding/binary"
	"fmt"
	"io"
)

// SectionTable manages reading/writing section entries
type SectionTable struct {
	Entries []SectionEntry
}

// FindSection returns the first section of given type
func (t *SectionTable) FindSection(stype SectionType) (*SectionEntry, error) {
	for i := range t.Entries {
		if t.Entries[i].Type == stype {
			return &t.Entries[i], nil
		}
	}
	return nil, fmt.Errorf("section type %d not found", stype)
}

// HasSection checks if a section type exists
func (t *SectionTable) HasSection(stype SectionType) bool {
	for i := range t.Entries {
		if t.Entries[i].Type == stype {
			return true
		}
	}
	return false
}

// ReadSectionTable reads the section table from a reader
func ReadSectionTable(r io.Reader, count uint32) (*SectionTable, error) {
	table := &SectionTable{
		Entries: make([]SectionEntry, count),
	}
	
	for i := uint32(0); i < count; i++ {
		var entry SectionEntry
		if err := binary.Read(r, binary.LittleEndian, &entry.Type); err != nil {
			return nil, fmt.Errorf("reading section type: %w", err)
		}
		if err := binary.Read(r, binary.LittleEndian, &entry.Offset); err != nil {
			return nil, fmt.Errorf("reading section offset: %w", err)
		}
		if err := binary.Read(r, binary.LittleEndian, &entry.Size); err != nil {
			return nil, fmt.Errorf("reading section size: %w", err)
		}
		if err := binary.Read(r, binary.LittleEndian, &entry.Flags); err != nil {
			return nil, fmt.Errorf("reading section flags: %w", err)
		}
		table.Entries[i] = entry
	}
	
	return table, nil
}

// WriteSectionTable writes the section table to a writer
func WriteSectionTable(w io.Writer, table *SectionTable) error {
	for _, entry := range table.Entries {
		if err := binary.Write(w, binary.LittleEndian, entry.Type); err != nil {
			return err
		}
		if err := binary.Write(w, binary.LittleEndian, entry.Offset); err != nil {
			return err
		}
		if err := binary.Write(w, binary.LittleEndian, entry.Size); err != nil {
			return err
		}
		if err := binary.Write(w, binary.LittleEndian, entry.Flags); err != nil {
			return err
		}
	}
	return nil
}

// SectionEntrySize is the byte size of a single section entry
const SectionEntrySize = 4 + 8 + 8 + 4 // Type + Offset + Size + Flags = 24 bytes