amfora/renderer/renderer.go

// Package renderer provides functions to convert various data into a cview primitive.
// Example objects include a Gemini response, and an error.
//
// Rendered lines always end with \r\n, in an effort to be Window compatible.
package renderer

import (
	urlPkg "net/url"
	"strconv"
	"strings"

	"github.com/spf13/viper"
	"gitlab.com/tslocum/cview"
)

// RenderPlainText should be used to format plain text pages.
func RenderPlainText(s string, leftMargin int) string {
	var shifted string
	lines := strings.Split(cview.Escape(s), "\n")
	for i := range lines {
		shifted += strings.Repeat(" ", leftMargin) + lines[i] + "\n"
	}
	return shifted
}

// wrapLine wraps a line to the provided width, and adds the provided prefix and suffix to each wrapped line.
// It recovers from wrapping panics and should never cause a panic.
// It returns a slice of lines, without newlines at the end.
//
// Set includeFirst to true if the prefix and suffix should be applied to the first wrapped line as well
func wrapLine(line string, width int, prefix, suffix string, includeFirst bool) []string {
	// Anonymous function to allow recovery from potential WordWrap panic
	var ret []string
	func() {
		defer func() {
			if r := recover(); r != nil {
				// Use unwrapped line instead
				if includeFirst {
					ret = []string{prefix + line + suffix}
				} else {
					ret = []string{line}
				}
			}
		}()

		wrapped := cview.WordWrap(line, width)
		for i := range wrapped {
			if !includeFirst && i == 0 {
				continue
			}
			wrapped[i] = prefix + wrapped[i] + suffix
		}
		ret = wrapped
	}()
	return ret
}

// convertRegularGemini converts non-preformatted blocks of text/gemini
// into a cview-compatible format.
// It also returns a slice of link URLs.
// numLinks is the number of links that exist so far.
// width is the number of columns to wrap to.
//
// Since this only works on non-preformatted blocks, RenderGemini
// should always be used instead.
func convertRegularGemini(s string, numLinks, width int) (string, []string) {
	links := make([]string, 0)
	lines := strings.Split(s, "\n")
	wrappedLines := make([]string, 0) // Final result

	for i := range lines {
		lines[i] = strings.TrimRight(lines[i], " \r\t\n")

		if strings.HasPrefix(lines[i], "#") {
			// Headings
			if viper.GetBool("a-general.color") {
				if strings.HasPrefix(lines[i], "###") {
					wrappedLines = append(wrappedLines, wrapLine(lines[i], width, "[fuchsia::b]", "[-::-]", true)...)
				} else if strings.HasPrefix(lines[i], "##") {
					wrappedLines = append(wrappedLines, wrapLine(lines[i], width, "[lime::b]", "[-::-]", true)...)
				} else if strings.HasPrefix(lines[i], "#") {
					wrappedLines = append(wrappedLines, wrapLine(lines[i], width, "[red::b]", "[-::-]", true)...)
				}
			} else {
				// Just bold, no colors
				wrappedLines = append(wrappedLines, wrapLine(lines[i], width, "[::b]", "[-::-]", true)...)
			}

			// Links
		} else if strings.HasPrefix(lines[i], "=>") && len([]rune(lines[i])) >= 3 {
			// Trim whitespace and separate link from link text

			lines[i] = strings.Trim(lines[i][2:], " \t") // Remove `=>` part too
			delim := strings.IndexAny(lines[i], " \t")   // Whitespace between link and link text

			var url string
			var linkText string
			if delim == -1 {
				// No link text
				url = lines[i]
				linkText = url
			} else {
				// There is link text
				url = lines[i][:delim]
				linkText = strings.Trim(lines[i][delim:], " \t")
			}

			if strings.TrimSpace(lines[i]) == "" || strings.TrimSpace(url) == "" {
				// Link was just whitespace, reset it and move on
				lines[i] = "=>"
				wrappedLines = append(wrappedLines, lines[i])
				continue
			}

			links = append(links, url)

			// Wrap and add link text

			// Wrap the link text, but add some spaces to indent the wrapped lines past the link number
			wrappedLink := wrapLine(linkText, width,
				strings.Repeat(" ", len(strconv.Itoa(numLinks+len(links)))+4), // +4 for spaces and brackets
				"",
				false, // Don't indent the first line, it's the one with link number
			)

			// Set the style tags
			// Add them to the first line

			if viper.GetBool("a-general.color") {
				pU, err := urlPkg.Parse(url)
				if err == nil && (pU.Scheme == "" || pU.Scheme == "gemini" || pU.Scheme == "about") {
					// A gemini link
					// Add the link text in blue (in a region), and a gray link number to the left of it
					wrappedLink[0] = `[silver::b][` + strconv.Itoa(numLinks+len(links)) + "[]" + "[-::-]  " +
						`[dodgerblue]["` + strconv.Itoa(numLinks+len(links)-1) + `"]` +
						wrappedLink[0]
				} else {
					// Not a gemini link, use purple instead
					wrappedLink[0] = `[silver::b][` + strconv.Itoa(numLinks+len(links)) + "[]" + "[-::-]  " +
						`[#8700d7]["` + strconv.Itoa(numLinks+len(links)-1) + `"]` +
						wrappedLink[0]
				}
			} else {
				// No colours allowed
				wrappedLink[0] = `[::b][` + strconv.Itoa(numLinks+len(links)) + "[][::-]  " +
					`["` + strconv.Itoa(numLinks+len(links)-1) + `"]` +
					wrappedLink[0]
			}

			wrappedLink[len(wrappedLink)-1] += `[""][-]` // Close region and formatting at the end

			wrappedLines = append(wrappedLines, wrappedLink...)

			// Lists
		} else if strings.HasPrefix(lines[i], "* ") {
			if viper.GetBool("a-general.bullets") {
				// Wrap list item, and indent wrapped lines past the bullet
				wrappedItem := wrapLine(lines[i][1:], width, "   ", "", false)
				// Add bullet
				wrappedItem[0] = " \u2022" + wrappedItem[0]
				wrappedLines = append(wrappedLines, wrappedItem...)
			}
			// Optionally list lines could be colored here too, if color is enabled
		} else if strings.HasPrefix(lines[i], ">") {
			// It's a quote line, add extra quote symbols and italics to the start of each wrapped line

			// Remove beginning quote and maybe space
			lines[i] = strings.TrimPrefix(lines[i], ">")
			lines[i] = strings.TrimPrefix(lines[i], " ")
			wrappedLines = append(wrappedLines, wrapLine(lines[i], width, "> [::i]", "[::-]", true)...)

		} else if strings.TrimSpace(lines[i]) == "" {
			// Just add empty line without processing
			wrappedLines = append(wrappedLines, "")
		} else {
			// Regular line, just wrap it
			wrappedLines = append(wrappedLines, wrapLine(lines[i], width, "", "", true)...)
		}
	}

	return strings.Join(wrappedLines, "\r\n"), links
}

// RenderGemini converts text/gemini into a cview displayable format.
// It also returns a slice of link URLs.
//
// width is the number of columns to wrap to.
// leftMargin is the number of blank spaces to prepend to each line.
func RenderGemini(s string, width, leftMargin int) (string, []string) {
	s = cview.Escape(s)
	if viper.GetBool("a-general.color") {
		s = cview.TranslateANSI(s)
	}
	lines := strings.Split(s, "\n")

	links := make([]string, 0)

	// Process and wrap non preformatted lines
	rendered := "" // Final result
	pre := false
	buf := "" // Block of regular or preformatted lines
	for i := range lines {
		if strings.HasPrefix(lines[i], "```") {
			if pre {
				// In a preformatted block, so add the text as is
				// Don't add the current line with backticks
				rendered += buf
			} else {
				// Not preformatted, regular text
				ren, lks := convertRegularGemini(buf, len(links), width)
				links = append(links, lks...)
				rendered += ren
			}
			buf = "" // Clear buffer for next block
			pre = !pre
			continue
		}
		// Lines always end with \r\n for Windows compatibility
		buf += strings.TrimSuffix(lines[i], "\r") + "\r\n"
	}
	// Gone through all the lines, but there still is likely a block in the buffer
	if pre {
		// File ended without closing the preformatted block
		rendered += buf
	} else {
		// Not preformatted, regular text
		// Same code as in the loop above
		ren, lks := convertRegularGemini(buf, len(links), width)
		links = append(links, lks...)
		rendered += ren
	}

	if leftMargin > 0 {
		renLines := strings.Split(rendered, "\n")
		for i := range renLines {
			renLines[i] = strings.Repeat(" ", leftMargin) + renLines[i]
		}
		return strings.Join(renLines, "\n"), links
	}

	return rendered, links
}