package goon

import (
	"io"
	"strconv"
)

// Some constants in the form of bytes to avoid string overhead.  This mirrors
// the technique used in the fmt package.
var (
	plusBytes             = []byte("+")
	iBytes                = []byte("i")
	trueBytes             = []byte("true")
	falseBytes            = []byte("false")
	interfaceBytes        = []byte("(interface{})")
	commaBytes            = []byte(",")
	commaNewlineBytes     = []byte(",\n")
	newlineBytes          = []byte("\n")
	openBraceBytes        = []byte("{")
	openBraceNewlineBytes = []byte("{\n")
	closeBraceBytes       = []byte("}")
	ampersandBytes        = []byte("&")
	colonSpaceBytes       = []byte(": ")
	openParenBytes        = []byte("(")
	closeParenBytes       = []byte(")")
	nilBytes              = []byte("nil")
	nilParenBytes         = []byte("(nil)")
	circularBytes         = []byte("already_shown")
	invalidAngleBytes     = []byte("<invalid>")
)

// hexDigits is used to map a decimal value to a hex digit.
var hexDigits = "0123456789abcdef"

// printBool outputs a boolean value as true or false to Writer w.
func printBool(w io.Writer, val bool) {
	if val {
		w.Write(trueBytes)
	} else {
		w.Write(falseBytes)
	}
}

// printInt outputs a signed integer value to Writer w.
func printInt(w io.Writer, val int64, base int) {
	w.Write([]byte(strconv.FormatInt(val, base)))
}

// printUint outputs an unsigned integer value to Writer w.
func printUint(w io.Writer, val uint64, base int) {
	w.Write([]byte(strconv.FormatUint(val, base)))
}

// printFloat outputs a floating point value using the specified precision,
// which is expected to be 32 or 64bit, to Writer w.
func printFloat(w io.Writer, val float64, precision int) {
	w.Write([]byte(strconv.FormatFloat(val, 'g', -1, precision)))
}

// printComplex outputs a complex value using the specified float precision
// for the real and imaginary parts to Writer w.
func printComplex(w io.Writer, c complex128, floatPrecision int) {
	r := real(c)
	w.Write(openParenBytes)
	w.Write([]byte(strconv.FormatFloat(r, 'g', -1, floatPrecision)))
	i := imag(c)
	if i >= 0 {
		w.Write(plusBytes)
	}
	w.Write([]byte(strconv.FormatFloat(i, 'g', -1, floatPrecision)))
	w.Write(iBytes)
	w.Write(closeParenBytes)
}

// printHexPtr outputs a uintptr formatted as hexidecimal with a leading '0x'
// prefix to Writer w.
func printHexPtr(w io.Writer, p uintptr) {
	// Null pointer.
	num := uint64(p)
	if num == 0 {
		w.Write(nilBytes)
		return
	}

	// Max uint64 is 16 bytes in hex + 2 bytes for '0x' prefix
	buf := make([]byte, 18)

	// It's simpler to construct the hex string right to left.
	base := uint64(16)
	i := len(buf) - 1
	for num >= base {
		buf[i] = hexDigits[num%base]
		num /= base
		i--
	}
	buf[i] = hexDigits[num]

	// Add '0x' prefix.
	i--
	buf[i] = 'x'
	i--
	buf[i] = '0'

	// Strip unused leading bytes.
	buf = buf[i:]
	w.Write(buf)
}