Move style and formatter API into chroma package.

colour.go

@@ -0,0 +1,85 @@
+package chroma
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// ANSI2RGB maps ANSI colour names, as supported by Chroma, to hex RGB values.
+var ANSI2RGB = map[string]string{
+	"#ansiblack":     "000000",
+	"#ansidarkred":   "7f0000",
+	"#ansidarkgreen": "007f00",
+	"#ansibrown":     "7f7fe0",
+	"#ansidarkblue":  "00007f",
+	"#ansipurple":    "7f007f",
+	"#ansiteal":      "007f7f",
+	"#ansilightgray": "e5e5e5",
+	// Normal
+	"#ansidarkgray":  "555555",
+	"#ansired":       "ff0000",
+	"#ansigreen":     "00ff00",
+	"#ansiyellow":    "ffff00",
+	"#ansiblue":      "0000ff",
+	"#ansifuchsia":   "ff00ff",
+	"#ansiturquoise": "00ffff",
+	"#ansiwhite":     "ffffff",
+}
+
+// Colour represents an RGB colour.
+type Colour int32
+
+// ParseColour in the forms #rgb, #rrggbb, or #ansi<colour>. Will panic
+// if colour is in an invalid format.
+func ParseColour(colour string) Colour {
+	colour = normaliseColour(colour)
+	n, err := strconv.ParseUint(colour, 16, 32)
+	if err != nil {
+		panic(err)
+	}
+	return Colour(n + 1)
+}
+
+func (c Colour) IsSet() bool { return c != 0 }
+
+func (c Colour) String() string   { return fmt.Sprintf("#%06x", int(c-1)) }
+func (c Colour) GoString() string { return fmt.Sprintf("Colour(0x%06x)", int(c-1)) }
+
+// Red component of colour.
+func (c Colour) Red() uint8 { return uint8(((c - 1) >> 16) & 0xff) }
+
+// Green component of colour.
+func (c Colour) Green() uint8 { return uint8(((c - 1) >> 8) & 0xff) }
+
+// Blue component of colour.
+func (c Colour) Blue() uint8 { return uint8((c - 1) & 0xff) }
+
+// Distance squared between two colours.
+func (c Colour) Distance(other Colour) int {
+	rd := int(c.Red() - other.Red())
+	gd := int(c.Green() - other.Green())
+	bd := int(c.Blue() - other.Blue())
+	return rd*rd + gd*gd + bd*bd
+}
+
+// Colours is an orderable set of colours.
+type Colours []Colour
+
+func (c Colours) Len() int           { return len(c) }
+func (c Colours) Swap(i, j int)      { c[i], c[j] = c[j], c[i] }
+func (c Colours) Less(i, j int) bool { return c[i] < c[j] }
+
+// Convert colours to #rrggbb.
+func normaliseColour(colour string) string {
+	if ansi, ok := ANSI2RGB[colour]; ok {
+		return ansi
+	}
+	if strings.HasPrefix(colour, "#") {
+		colour = colour[1:]
+		if len(colour) == 3 {
+			return colour[0:1] + colour[0:1] + colour[1:2] + colour[1:2] + colour[2:3] + colour[2:3]
+		}
+	}
+	return colour
+}