package coverage

import (
	"bufio"
	"fmt"
	"io"
	"strconv"
	"strings"
)

// Parse creates a coverage files struct from a coverage file format
// you must provide @gopkg which is the package name
func Parse(r io.Reader, gopkg string) (*Files, error) {
	reader := bufio.NewReader(r)
	eof := false
	var n uint = 0

	files := &Files{
		files:       make(map[string]File),
		packagePath: gopkg,
	}

	// read loop
	for true {
		n++
		if eof {
			break
		}

		notrim, err := reader.ReadString('\n')
		if err == io.EOF {
			if len(notrim) > 0 {
				eof = true
			} else {
				break
			}
		}

		line := strings.Trim(notrim, " \t\r\n")
		if len(line) < 1 {
			continue
		}

		// ignore first line
		if n == 1 && line == "mode: set" {
			continue
		}

		// extract features from line
		var cover = Coverage{}

		// format: filename:startLine.startColumn,endLine.endColumn occurences count
		splitFile := strings.Split(line, ":")
		if len(splitFile) != 2 {
			return nil, fmt.Errorf("invalid format line %d", n)
		}
		filename := splitFile[0]
		if !strings.HasPrefix(filename, gopkg) {
			return nil, fmt.Errorf("invalid package name '%s' on line %d", gopkg, n)
		}
		filename = strings.TrimPrefix(filename, gopkg)
		if len(filename) < 2 {
			return nil, fmt.Errorf("invalid format line %d", n)
		}
		// remove starting '/'
		if filename[0] == '/' {
			filename = filename[1:]
		}

		splitSpace := strings.Split(splitFile[1], " ")
		if len(splitSpace) != 3 {
			return nil, fmt.Errorf("invalid format line %d", n)
		}

		separators := strings.Split(splitSpace[0], ",")
		if len(separators) != 2 {
			return nil, fmt.Errorf("invalid format line %d", n)
		}

		splitStart := strings.Split(separators[0], ".")
		if len(splitStart) != 2 {
			return nil, fmt.Errorf("invalid format line %d", n)
		}
		cover.StartLine, err = strconv.ParseUint(splitStart[0], 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid format line %d", n)
		}
		cover.StartColumn, err = strconv.ParseUint(splitStart[1], 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid format line %d", n)
		}

		splitEnd := strings.Split(separators[1], ".")
		if len(splitEnd) != 2 {
			return nil, fmt.Errorf("invalid format line %d", n)
		}
		cover.EndLine, err = strconv.ParseUint(splitEnd[0], 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid format line %d", n)
		}
		cover.EndColumn, err = strconv.ParseUint(splitEnd[1], 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid format line %d", n)
		}

		// append to files
		_, isset := files.files[filename]
		if !isset {
			files.files[filename] = make(File, 0)
		}
		files.files[filename] = append(files.files[filename], cover)

	}

	return files, nil
}