var glslifyBundle = require('glslify-bundle')
var glslifyDeps   = require('glslify-deps/sync')
var nodeResolve   = require('resolve')
var path          = require('path')
var extend        = require('xtend')
var stackTrace    = require('stack-trace')

module.exports = function(arg, opts) {
  var isShaderString = /(void\s+main\s?\(.*\)|\n)/.test(arg)
  if (Array.isArray(arg)) { // template string
    return iface().tag.apply(null, arguments)
  } else if (typeof arg === 'string' && !isShaderString && opts && opts._flags) {
    // browserify transform
    return require('./transform.js').apply(this, arguments)
  } else if (typeof arg === 'string' && isShaderString) { // source string
    return iface().compile(arg, opts)
  } else if (typeof arg === 'string') { // source file
    return iface().file(arg, opts)
  } else throw new Error('unhandled argument type: ' + typeof arg)
}
module.exports.compile = function(src, opts) {
  return iface().compile(src, opts)
}
module.exports.file = function(file, opts) {
  return iface().file(file, opts)
}

function iface () {
  try { var basedir = path.dirname(stackTrace.get()[2].getFileName()) }
  catch (err) { basedir = process.cwd() }
  var posts = []
  return { tag: tag, compile: compile, file: file }

  function tag(strings) {
    if (typeof strings === 'string') strings = [strings]
    var exprs = [].slice.call(arguments, 1)
    var parts = []
    for (var i = 0; i < strings.length-1; i++) {
      parts.push(strings[i], exprs[i] || '')
    }
    parts.push(strings[i])
    return compile(parts.join(''))
  }
  function compile(src, opts) {
    if (!opts) opts = {}
    var depper = gdeps(opts)
    var deps = depper.inline(src, opts.basedir || basedir)
    return bundle(deps)
  }
  function file(filename, opts) {
    if (!opts) opts = {}
    var depper = gdeps(opts)
    var deps = depper.add(path.resolve(opts.basedir || basedir, filename))
    return bundle(deps)
  }
  function gdeps (opts) {
    if (!opts) opts = {}
    var depper = glslifyDeps({ cwd: opts.basedir || basedir })
    var transforms = opts.transform || []
    transforms = Array.isArray(transforms) ? transforms : [transforms]
    transforms.forEach(function(transform) {
      transform = Array.isArray(transform) ? transform : [transform]
      var name = transform[0]
      var opts = transform[1] || {}
      if (opts.post) {
        posts.push({ name: name, opts: opts })
      } else {
        depper.transform(name, opts)
      }
    })
    return depper
  }
  function bundle (deps) {
    var source = glslifyBundle(deps)
    posts.forEach(function (tr) {
      if (typeof tr.name === 'function') {
        var transform = tr.name
      } else {
        var target = nodeResolve.sync(tr.name, { basedir: basedir })
        var transform = require(target)
      }
      var src = transform((deps && deps[0] && deps[0].file) || null, source, { post: true })
      if (src) source = src
    })
    return source
  }
}