// Package csv provides utilities for loading and working with CSV data.
package csv

import (
	"encoding/csv"
	"io"
	"os"

	"git.sdf.org/jchenry/x"
	osx "git.sdf.org/jchenry/x/os"
)

// CSV represents parsed CSV data with a header row and data rows.
type CSV struct {
	// Header contains the column names from the first row
	Header []string
	// Data contains all remaining rows
	Data [][]string
}

// LoadCSVFromFile loads CSV data from a file, treating the first row as a header.
// The file must not be nil or this function will panic.
// Returns the parsed CSV data or an error if reading fails.
func LoadCSVFromFile(f *os.File) (c *CSV, err error) {
	x.Assert(f != nil, "LoadCSVFromFile: f is nil")
	csvFile := osx.FileOrStdin(f)
	defer csvFile.Close()
	return LoadCSVFromReader(csvFile)
}

// LoadCSVFromReader loads CSV data from a reader, treating the first row as a header.
// The reader must not be nil or this function will panic.
// Returns the parsed CSV data or an error if reading fails.
func LoadCSVFromReader(r io.Reader) (c *CSV, err error) {
	x.Assert(r != nil, "LoadCSVFromReader: r is nil")
	reader := csv.NewReader(r)

	header, err := reader.Read()
	if err != nil {
		return nil, err
	}

	data, err := reader.ReadAll()
	if err != nil {
		return nil, err
	}

	csvData := &CSV{
		Header: header,
		Data:   data,
	}

	return csvData, nil
}