47 lines
1.4 KiB
Go
47 lines
1.4 KiB
Go
package step
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import "strings"
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const frontMatterRule = "---"
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// FrontMatter represents optional metadata that can occur at the very start of
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// a document.
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type FrontMatter = map[string] string
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// SplitFrontMatter parses the front matter (if it exists), returning a map
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// representing it along with the rest of the input as a string. If there is no
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// front matter, an empty map will be returned.
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func SplitFrontMatter (input string) (FrontMatter, string, error) {
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if !strings.HasPrefix(input, frontMatterRule + "\n") {
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// no front matter at all
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return FrontMatter { }, input, nil
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}
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input = strings.TrimPrefix(input, frontMatterRule)
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index := strings.Index(input, "\n" + frontMatterRule + "\n")
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if index < 0 {
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return nil, "", ErrFrontMatterNeverClosed
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}
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frontMatterRaw := input[:index]
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body := input[index + len(frontMatterRule) + 2:]
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frontMatter := make(FrontMatter)
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for _, line := range strings.Split(frontMatterRaw, "\n") {
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line = strings.TrimSpace(line)
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if line == "" { continue }
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key, value, ok := strings.Cut(line, ":")
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if !ok {
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return nil, "", ErrFrontMatterMalformed
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}
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key = strings.ToLower(strings.TrimSpace(key))
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value = strings.TrimSpace(value)
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if key == "" {
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return nil, "", ErrFrontMatterMalformed
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}
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if _, exists := frontMatter[key]; exists {
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return nil, "", ErrFrontMatterDuplicateKey
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}
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frontMatter[key] = value
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}
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return frontMatter, body, nil
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}
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