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Merge pull request #61 from cli/tableprinter
Extract table printer from CLI
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,242 @@ | ||
| // Package tableprinter facilitates rendering column-formatted data to a terminal and TSV-formatted data to | ||
| // a script or a file. It is suitable for presenting tabular data in a human-readable format that is | ||
| // guaranteed to fit within the given viewport, while at the same time offering the same data in a | ||
| // machine-readable format for scripts. | ||
| package tableprinter | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "io" | ||
| "strings" | ||
|
|
||
| "github.com/mattn/go-runewidth" | ||
| ) | ||
|
|
||
| type fieldOption func(*tableField) | ||
|
|
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| type TablePrinter interface { | ||
| AddField(string, ...fieldOption) | ||
| EndRow() | ||
| Render() error | ||
| } | ||
|
|
||
| // WithTruncate overrides the truncation function for the field. The function should transform a string | ||
| // argument into a string that fits within the given display width. The default behavior is to truncate the | ||
| // value by adding "..." in the end. Pass nil to disable truncation for this value. | ||
| func WithTruncate(fn func(int, string) string) fieldOption { | ||
| return func(f *tableField) { | ||
| f.truncateFunc = fn | ||
| } | ||
| } | ||
|
|
||
| // WithColor sets the color function for the field. The function should transform a string value by wrapping | ||
| // it in ANSI escape codes. The color function will not be used if the table was initialized in non-terminal mode. | ||
| func WithColor(fn func(string) string) fieldOption { | ||
| return func(f *tableField) { | ||
| f.colorFunc = fn | ||
| } | ||
| } | ||
|
|
||
| // New initializes a table printer with terminal mode and terminal width. When terminal mode is enabled, the | ||
| // output will be human-readable, column-formatted to fit available width, and rendered with color support. | ||
| // In non-terminal mode, the output is tab-separated and all truncation of values is disabled. | ||
| func New(w io.Writer, isTTY bool, maxWidth int) TablePrinter { | ||
| if isTTY { | ||
| return &ttyTablePrinter{ | ||
| out: w, | ||
| maxWidth: maxWidth, | ||
| } | ||
| } | ||
| return &tsvTablePrinter{ | ||
| out: w, | ||
| } | ||
| } | ||
|
|
||
| type tableField struct { | ||
| text string | ||
| truncateFunc func(int, string) string | ||
| colorFunc func(string) string | ||
| } | ||
|
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| type ttyTablePrinter struct { | ||
| out io.Writer | ||
| maxWidth int | ||
| rows [][]tableField | ||
| } | ||
|
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| func (t *ttyTablePrinter) AddField(s string, opts ...fieldOption) { | ||
| if t.rows == nil { | ||
| t.rows = make([][]tableField, 1) | ||
| } | ||
| rowI := len(t.rows) - 1 | ||
| field := tableField{ | ||
| text: s, | ||
| truncateFunc: truncateText, | ||
| } | ||
| for _, opt := range opts { | ||
| opt(&field) | ||
| } | ||
| t.rows[rowI] = append(t.rows[rowI], field) | ||
| } | ||
|
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| func (t *ttyTablePrinter) EndRow() { | ||
| t.rows = append(t.rows, []tableField{}) | ||
| } | ||
|
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| func (t *ttyTablePrinter) Render() error { | ||
| if len(t.rows) == 0 { | ||
| return nil | ||
| } | ||
|
|
||
| delim := " " | ||
| numCols := len(t.rows[0]) | ||
| colWidths := t.calculateColumnWidths(len(delim)) | ||
|
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| for _, row := range t.rows { | ||
| for col, field := range row { | ||
| if col > 0 { | ||
| _, err := fmt.Fprint(t.out, delim) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| } | ||
| truncVal := field.text | ||
| if field.truncateFunc != nil { | ||
| truncVal = field.truncateFunc(colWidths[col], field.text) | ||
| } | ||
| if col < numCols-1 { | ||
| // pad value with spaces on the right | ||
| if padWidth := colWidths[col] - displayWidth(field.text); padWidth > 0 { | ||
| truncVal += strings.Repeat(" ", padWidth) | ||
| } | ||
| } | ||
| if field.colorFunc != nil { | ||
| truncVal = field.colorFunc(truncVal) | ||
| } | ||
| _, err := fmt.Fprint(t.out, truncVal) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| } | ||
| if len(row) > 0 { | ||
| _, err := fmt.Fprint(t.out, "\n") | ||
| if err != nil { | ||
| return err | ||
| } | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
|
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| func (t *ttyTablePrinter) calculateColumnWidths(delimSize int) []int { | ||
| numCols := len(t.rows[0]) | ||
| maxColWidths := make([]int, numCols) | ||
| colWidths := make([]int, numCols) | ||
|
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| for _, row := range t.rows { | ||
| for col, field := range row { | ||
| w := displayWidth(field.text) | ||
| if w > maxColWidths[col] { | ||
| maxColWidths[col] = w | ||
| } | ||
| // if this field has disabled truncating, ensure that the column is wide enough | ||
| if field.truncateFunc == nil && w > colWidths[col] { | ||
| colWidths[col] = w | ||
| } | ||
| } | ||
| } | ||
|
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| availWidth := func() int { | ||
| setWidths := 0 | ||
| for col := 0; col < numCols; col++ { | ||
| setWidths += colWidths[col] | ||
| } | ||
| return t.maxWidth - delimSize*(numCols-1) - setWidths | ||
| } | ||
| numFixedCols := func() int { | ||
| fixedCols := 0 | ||
| for col := 0; col < numCols; col++ { | ||
| if colWidths[col] > 0 { | ||
| fixedCols++ | ||
| } | ||
| } | ||
| return fixedCols | ||
| } | ||
|
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||
| // set the widths of short columns | ||
| if w := availWidth(); w > 0 { | ||
| if numFlexColumns := numCols - numFixedCols(); numFlexColumns > 0 { | ||
| perColumn := w / numFlexColumns | ||
| for col := 0; col < numCols; col++ { | ||
| if max := maxColWidths[col]; max < perColumn { | ||
| colWidths[col] = max | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| // truncate long columns to the remaining available width | ||
| if numFlexColumns := numCols - numFixedCols(); numFlexColumns > 0 { | ||
| perColumn := availWidth() / numFlexColumns | ||
| for col := 0; col < numCols; col++ { | ||
| if colWidths[col] == 0 { | ||
| if max := maxColWidths[col]; max < perColumn { | ||
| colWidths[col] = max | ||
| } else if perColumn > 0 { | ||
| colWidths[col] = perColumn | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| // add the remainder to truncated columns | ||
| if w := availWidth(); w > 0 { | ||
| for col := 0; col < numCols; col++ { | ||
| d := maxColWidths[col] - colWidths[col] | ||
| toAdd := w | ||
| if d < toAdd { | ||
| toAdd = d | ||
| } | ||
| colWidths[col] += toAdd | ||
| w -= toAdd | ||
| if w <= 0 { | ||
| break | ||
| } | ||
| } | ||
| } | ||
|
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| return colWidths | ||
| } | ||
|
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| type tsvTablePrinter struct { | ||
| out io.Writer | ||
| currentCol int | ||
| } | ||
|
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| func (t *tsvTablePrinter) AddField(text string, opts ...fieldOption) { | ||
| if t.currentCol > 0 { | ||
| fmt.Fprint(t.out, "\t") | ||
| } | ||
| fmt.Fprint(t.out, text) | ||
| t.currentCol++ | ||
| } | ||
|
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| func (t *tsvTablePrinter) EndRow() { | ||
| fmt.Fprint(t.out, "\n") | ||
| t.currentCol = 0 | ||
| } | ||
|
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| func (t *tsvTablePrinter) Render() error { | ||
| return nil | ||
| } | ||
|
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| func truncateText(maxWidth int, s string) string { | ||
| if maxWidth < 5 { | ||
| return runewidth.Truncate(s, maxWidth, "") | ||
| } | ||
| return runewidth.Truncate(s, maxWidth, "...") | ||
| } | ||
|
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| func displayWidth(s string) int { | ||
| return runewidth.StringWidth(s) | ||
| } |
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