135 lines
3.3 KiB
Go
135 lines
3.3 KiB
Go
package columnize
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import (
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"fmt"
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"strings"
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)
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type Config struct {
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// The string by which the lines of input will be split.
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Delim string
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// The string by which columns of output will be separated.
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Glue string
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// The string by which columns of output will be prefixed.
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Prefix string
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// A replacement string to replace empty fields
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Empty string
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}
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// Returns a Config with default values.
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func DefaultConfig() *Config {
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return &Config{
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Delim: "|",
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Glue: " ",
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Prefix: "",
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}
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}
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// Returns a list of elements, each representing a single item which will
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// belong to a column of output.
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func getElementsFromLine(config *Config, line string) []interface{} {
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elements := make([]interface{}, 0)
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for _, field := range strings.Split(line, config.Delim) {
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value := strings.TrimSpace(field)
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if value == "" && config.Empty != "" {
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value = config.Empty
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}
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elements = append(elements, value)
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}
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return elements
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}
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// Examines a list of strings and determines how wide each column should be
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// considering all of the elements that need to be printed within it.
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func getWidthsFromLines(config *Config, lines []string) []int {
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var widths []int
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for _, line := range lines {
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elems := getElementsFromLine(config, line)
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for i := 0; i < len(elems); i++ {
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l := len(elems[i].(string))
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if len(widths) <= i {
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widths = append(widths, l)
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} else if widths[i] < l {
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widths[i] = l
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}
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}
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}
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return widths
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}
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// Given a set of column widths and the number of columns in the current line,
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// returns a sprintf-style format string which can be used to print output
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// aligned properly with other lines using the same widths set.
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func (c *Config) getStringFormat(widths []int, columns int) string {
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// Start with the prefix, if any was given.
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stringfmt := c.Prefix
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// Create the format string from the discovered widths
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for i := 0; i < columns && i < len(widths); i++ {
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if i == columns-1 {
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stringfmt += "%s\n"
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} else {
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stringfmt += fmt.Sprintf("%%-%ds%s", widths[i], c.Glue)
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}
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}
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return stringfmt
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}
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// MergeConfig merges two config objects together and returns the resulting
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// configuration. Values from the right take precedence over the left side.
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func MergeConfig(a, b *Config) *Config {
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var result Config = *a
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// Return quickly if either side was nil
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if a == nil || b == nil {
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return &result
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}
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if b.Delim != "" {
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result.Delim = b.Delim
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}
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if b.Glue != "" {
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result.Glue = b.Glue
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}
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if b.Prefix != "" {
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result.Prefix = b.Prefix
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}
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if b.Empty != "" {
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result.Empty = b.Empty
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}
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return &result
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}
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// Format is the public-facing interface that takes either a plain string
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// or a list of strings and returns nicely aligned output.
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func Format(lines []string, config *Config) string {
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var result string
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conf := MergeConfig(DefaultConfig(), config)
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widths := getWidthsFromLines(conf, lines)
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// Create the formatted output using the format string
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for _, line := range lines {
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elems := getElementsFromLine(conf, line)
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stringfmt := conf.getStringFormat(widths, len(elems))
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result += fmt.Sprintf(stringfmt, elems...)
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}
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// Remove trailing newline without removing leading/trailing space
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if n := len(result); n > 0 && result[n-1] == '\n' {
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result = result[:n-1]
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}
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return result
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}
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// Convenience function for using Columnize as easy as possible.
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func SimpleFormat(lines []string) string {
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return Format(lines, nil)
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}
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