package main

import ( "bufio" "bytes" "io" "path" "strings"

"github.com/johnstarich/go/regext"

)

func prepREADME(readme io.Reader) string { scanner := bufio.NewScanner(readme) showing := false codeFence := false var buf bytes.Buffer for scanner.Scan() { line := scanner.Text() line = convertToAbsoluteLinks(line)

	switch {
	case strings.HasPrefix(line, `<!-- SHOW `) && strings.HasSuffix(line, ` -->`):
		showing = true
	case strings.HasPrefix(line, `<!-- END SHOW `) && strings.HasSuffix(line, ` -->`):
		showing = false
	case line == "" && buf.Len() == 0: // skip leading blank lines
	case showing:
		const codeFenceStr = "```"
		switch {
		case codeFence && strings.HasPrefix(line, codeFenceStr):
			codeFence = false
		case strings.HasPrefix(line, codeFenceStr):
			codeFence = true
		case codeFence:
			buf.WriteString("    ") // indent code line
			buf.WriteString(line)
			buf.WriteRune('\n')
		default:
			buf.WriteString(line)
			buf.WriteRune('\n')
		}
	}
}
if err := scanner.Err(); err != nil {
	panic(err)
}
return buf.String()

}

// convertToAbsoluteLinks replaces relative links with absolute links to the repo func convertToAbsoluteLinks(s string) string { type readmeReplacement struct { newText string start, end int }

const urlPrefix = "https://github.com/IBM/cloud-operators/blob/master"
markdownLinkRe := regext.MustCompile(`
	\[
		[^ \] ]*      # link text
	\]
	\(
		( [^ \) ]* )  # capture link URL (capture group index 1)
	\)
`)

matches := markdownLinkRe.FindAllStringSubmatchIndex(s, -1)
var replacements []readmeReplacement
for _, match := range matches {
	start, end := match[2], match[3]
	linkPath := s[start:end]
	if strings.Contains(linkPath, "://") || strings.HasPrefix(linkPath, "#") {
		// skip absolute URLs or anchor-only URLs
		continue
	}
	linkPath = urlPrefix + path.Join("/", linkPath)
	replacements = append(replacements, readmeReplacement{
		newText: linkPath,
		start:   start,
		end:     end,
	})
}
for i := len(replacements) - 1; i >= 0; i-- {
	// replace matches going backward, so indexes don't change
	r := replacements[i]
	s = s[:r.start] + r.newText + s[r.end:]
}
return s

}