// Ported to Go by Dmitry Chestnykh. Porting is public domain,
// but the code should be used according to the original license,
// as it's a derivative work:
/* jsmin.c
   2013-03-29

Copyright (c) 2002 Douglas Crockford  (www.crockford.com)

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

The Software shall be used for Good, not Evil.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

// Package jsmin implements JavaScript minifier. It's a direct port of Doulas Crockford's JSMin.
package jsmin

// ... or should I say, a direct braindead port of the ugly Crockford's code...

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
)

const eof = -1

type minifier struct {
	buf          *bytes.Buffer
	r            *bufio.Reader
	w            *bufio.Writer
	theA         int
	theB         int
	theLookahead int
	theX         int
	theY         int
	err          error
}

func (m *minifier) init(r *bufio.Reader, w *bufio.Writer) {
	m.r = r
	m.w = w
	m.theLookahead = eof
	m.theX = eof
	m.theY = eof
}

func (m *minifier) error(s string) error {
	m.err = fmt.Errorf("JSMIN Error: %s", s)
	return m.err
}

/* isAlphanum -- return true if the character is a letter, digit, underscore,
   dollar sign, or non-ASCII character.
*/

func isAlphanum(c int) bool {
	return (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') ||
		(c >= 'A' && c <= 'Z') || c == '_' || c == '$' || c == '\\' ||
		c > 126
}

/* get -- return the next character from stdin. Watch out for lookahead. If
   the character is a control character, translate it to a space or
   linefeed.
*/

func (m *minifier) get() int {
	c := m.theLookahead
	m.theLookahead = eof
	if c == eof {
		b, err := m.r.ReadByte()
		if err != nil {
			if err == io.EOF {
				c = eof
			} else {
				m.error(err.Error())
				return eof
			}
		} else {
			c = int(b)
		}
	}
	if c >= ' ' || c == '\n' || c == eof {
		return c
	}
	if c == '\r' {
		return '\n'
	}
	return ' '
}

/* peek -- get the next character without getting it.
 */

func (m *minifier) peek() int {
	m.theLookahead = m.get()
	return m.theLookahead
}

/* next -- get the next character, excluding comments. peek() is used to see
   if a '/' is followed by a '/' or '*'.
*/

func (m *minifier) next() int {
	c := m.get()
	if c == '/' {
		switch m.peek() {
		case '/':
			for {
				c = m.get()
				if c <= '\n' {
					break
				}
			}
		case '*':
			m.get()
			// Preserve license comments (/*!)
			if m.peek() == '!' {
				m.get()
				m.putc('/')
				m.putc('*')
				m.putc('!')
				for c != 0 {
					c = m.get()
					switch c {
					case '*':
						if m.peek() == '/' {
							m.get()
							c = 0
						}
						break
					case eof:
						m.error("Unterminated comment.")
						return eof
					default:
						m.putc(c)
					}
				}
				m.putc('*')
				m.putc('/')
			}
			// --
			for c != ' ' {
				switch m.get() {
				case '*':
					if m.peek() == '/' {
						m.get()
						c = ' '
					}
					break
				case eof:
					m.error("Unterminated comment.")
					return eof
				}
			}
		}
	}
	m.theY = m.theX
	m.theX = c
	return c
}

/* action -- do something! What you do is determined by the argument:
        1   Output A. Copy B to A. Get the next B.
        2   Copy B to A. Get the next B. (Delete A).
        3   Get the next B. (Delete B).
   action treats a string as a single character. Wow!
   action recognizes a regular expression if it is preceded by ( or , or =.
*/
func (m *minifier) putc(c int) {
	m.w.WriteByte(byte(c))
}

func (m *minifier) action(d int) {
	switch d {
	case 1:
		m.putc(m.theA)
		if (m.theY == '\n' || m.theY == ' ') &&
			(m.theA == '+' || m.theA == '-' || m.theA == '*' || m.theA == '/') &&
			(m.theB == '+' || m.theB == '-' || m.theB == '*' || m.theB == '/') {
			m.putc(m.theY)
		}
		fallthrough
	case 2:
		m.theA = m.theB
		if m.theA == '\'' || m.theA == '"' || m.theA == '`' {
			for {
				m.putc(m.theA)
				m.theA = m.get()
				if m.theA == m.theB {
					break
				}
				if m.theA == '\\' {
					m.putc(m.theA)
					m.theA = m.get()
				}
				if m.theA == eof {
					m.error("Unterminated string literal.")
					return
				}
			}
		}
		fallthrough
	case 3:
		m.theB = m.next()
		if m.theB == '/' && (m.theA == '(' || m.theA == ',' || m.theA == '=' || m.theA == ':' ||
			m.theA == '[' || m.theA == '!' || m.theA == '&' || m.theA == '|' ||
			m.theA == '?' || m.theA == '+' || m.theA == '-' || m.theA == '~' ||
			m.theA == '*' || m.theA == '/' || m.theA == '{' || m.theA == '\n') {
			m.putc(m.theA)
			if m.theA == '/' || m.theA == '*' {
				m.putc(' ')
			}
			m.putc(m.theB)
			for {
				m.theA = m.get()
				if m.theA == '[' {
					for {
						m.putc(m.theA)
						m.theA = m.get()
						if m.theA == ']' {
							break
						}
						if m.theA == '\\' {
							m.putc(m.theA)
							m.theA = m.get()
						}
						if m.theA == eof {
							m.error("Unterminated set in Regular Expression literal.")
							return
						}
					}
				} else if m.theA == '/' {
					switch m.peek() {
					case '/', '*':
						m.error("Unterminated set in Regular Expression literal.")
						return
					}
					break
				} else if m.theA == '\\' {
					m.putc(m.theA)
					m.theA = m.get()
				}
				if m.theA == eof {
					m.error("Unterminated Regular Expression literal.")
					return
				}
				m.putc(m.theA)
			}
			m.theB = m.next()
		}
	}
}

/* jsmin -- Copy the input to the output, deleting the characters which are
   insignificant to JavaScript. Comments will be removed. Tabs will be
   replaced with spaces. Carriage returns will be replaced with linefeeds.
   Most spaces and linefeeds will be removed.
*/

func (m *minifier) run() {
	if m.peek() == 0xEF {
		m.get()
		m.get()
		m.get()
	}
	m.theA = '\n'
	m.action(3)
	for m.theA != eof {
		switch m.theA {
		case ' ':
			if isAlphanum(m.theB) {
				m.action(1)
			} else {
				m.action(2)
			}
		case '\n':
			switch m.theB {
			case '{', '[', '(', '+', '-', '!', '~':
				m.action(1)
			case ' ':
				m.action(3)
			default:
				if isAlphanum(m.theB) {
					m.action(1)
				} else {
					m.action(2)
				}
			}
		default:
			switch m.theB {
			case ' ':
				if isAlphanum(m.theA) {
					m.action(1)
				} else {
					m.action(3)
				}
			case '\n':
				switch m.theA {
				case '}', ']', ')', '+', '-', '"', '\'', '`':
					m.action(1)
				default:
					if isAlphanum(m.theA) {
						m.action(1)
					} else {
						m.action(3)
					}
				}
			default:
				m.action(1)
			}
		}
	}
}

// Minify returns a minified script or an error.
func Minify(script []byte) (minified []byte, err error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)
	r := bufio.NewReader(bytes.NewReader(script))

	m := new(minifier)
	m.init(r, w)
	m.run()
	if m.err != nil {
		return nil, err
	}
	w.Flush()

	minified = buf.Bytes()
	if len(minified) > 0 && minified[0] == '\n' {
		minified = minified[1:]
	}
	return minified, nil
}
