77 lines
1.5 KiB
Go
77 lines
1.5 KiB
Go
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package scanner
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import (
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"bufio"
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"fmt"
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"io"
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"regexp"
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"strings"
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"github.com/hashicorp/go-envparse"
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)
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var envvarRegex = regexp.MustCompile(`\$\{?([A-Z][A-Z0-9_]*)\}?`)
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type Scanner struct {
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envfile, r io.Reader
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w io.Writer
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}
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// New returns a new Scanner with the provided arguments.
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func New(w io.Writer, r io.Reader, envfile io.Reader) *Scanner {
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return &Scanner{
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w: w,
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r: r,
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envfile: envfile,
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}
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}
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const nl = "\n"
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func (s *Scanner) Scan() error {
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vars, err := envparse.Parse(s.envfile)
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if err != nil {
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return fmt.Errorf("error parsing envfile: %v", err)
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}
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scanner := bufio.NewScanner(s.r)
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for scanner.Scan() {
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text := scanner.Text()
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matchIndices := envvarRegex.FindAllStringSubmatchIndex(text, -1)
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var sb strings.Builder
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var c int
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for _, idx := range matchIndices {
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m1, m2, n1, n2 := idx[0], idx[1], idx[2], idx[3]
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writeString(&sb, text[c:m1])
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c = m2
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name := text[n1:n2]
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if val, ok := vars[name]; ok {
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writeString(&sb, val)
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} else {
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writeString(&sb, text[m1:m2])
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}
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}
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writeString(&sb, text[c:])
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writeString(&sb, nl)
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if _, err := s.w.Write([]byte(sb.String())); err != nil {
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return fmt.Errorf("error writing to output: %v", err)
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}
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}
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if err := scanner.Err(); err != nil {
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return fmt.Errorf("error reading input: %v", err)
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}
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return nil
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}
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// writeString writes a string to a StringBuilder, discarding the result and
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// (non-existent) error.
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func writeString(sb *strings.Builder, s string) {
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_, _ = sb.WriteString(s)
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}
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