package buildfile

import (
	"bufio"
	"errors"
	"git.xdrm.io/xdrm-brackets/nix-amer/internal/instruction"
	"io"
	"strings"
)

var ErrNullContext = errors.New("null context")

// Reader is the buildfile reader
type Reader struct {
	// Context is the linux distribution-specified execution context (package manager, service manager, etc)
	Context *instruction.ExecutionContext
	// Content is the instruction list
	Content []instruction.T
}

// NewReader creates a new reader for the specified build file and linux distribution
func NewReader(ctx *instruction.ExecutionContext, buildfile io.Reader) (*Reader, error) {

	// fail on null context
	if ctx == nil {
		return nil, ErrNullContext
	}

	r := &Reader{
		Context: ctx,
		Content: make([]instruction.T, 0),
	}

	// add each line as instruction
	l, reader := 0, bufio.NewReader(buildfile)
	for {
		l++

		// read line until end
		line, err := reader.ReadString('\n')
		if err == io.EOF {
			break
		} else if err != nil {
			return nil, LineError{l, err}
		}
		line = strings.Trim(line, " \t\r\n")

		// ignore newline & comments
		if len(line) < 1 || line[0] == '[' {
			continue
		}

		// turn into instruction
		inst, err := instruction.Parse(line)
		if err != nil {
			return nil, LineError{l, err}
		}

		// add to list
		r.Content = append(r.Content, inst)

	}

	return r, nil
}