add parse implementation as state machine

code/parse.js

@@ -0,0 +1,195 @@
+// states.js
+const go = 'gogogo'
+const good = 'good'
+const equals = 'equals'
+const dictSeparator = 'dictSeparator'
+const arraySeparator = 'arraySeparator'
+const firstDictKey = 'firstDictKey'
+const dictKey = 'dictKey'
+const dictValue = 'dictValue'
+const firstArrayValue = 'firstArrayValue'
+const arrayValue = 'arrayValue'
+
+let state
+let stack
+let container
+let key
+let value
+
+const escapes = {
+  '\\': '\\',
+  '"': '"'
+}
+
+const escape = string =>
+  string.replace(/\\(.)/g, (_, character) => escapes[character])
+
+// TODO add support for binary data
+const tokens = /^\s*(?:([,;=(){}])|"((?:[^\\"]|\\["\\])*)")/
+
+// string.js
+const stringAction = {
+  [go] () {
+    state = good
+  },
+  [firstDictKey] () {
+    key = value
+    state = equals
+  },
+  [dictKey] () {
+    key = value
+    state = equals
+  },
+  [dictValue] () {
+    state = dictSeparator
+  },
+  [firstArrayValue] () {
+    state = arraySeparator
+  },
+  [arrayValue] () {
+    state = arraySeparator
+  }
+}
+
+const action = {
+  '{': {
+    [go] () {
+      stack.push({state: good})
+      container = {}
+      state = firstDictKey
+    },
+    [dictValue] () {
+      stack.push({
+        container,
+        key,
+        state: dictSeparator
+      })
+      container = {}
+      state = firstDictKey
+    },
+    [firstArrayValue] () {
+      stack.push({
+        container,
+        state: arraySeparator
+      })
+      container = {}
+      state = firstDictKey
+    },
+    [arrayValue] () {
+      stack.push({
+        container,
+        state: arraySeparator
+      })
+      container = {}
+      state = firstDictKey
+    }
+  },
+  '}': {
+    [firstDictKey] () {
+      const last = stack.pop()
+      value = container
+      container = last.container
+      key = last.key
+      state = last.state
+    },
+    [dictSeparator] () {
+      const last = stack.pop()
+      container[key] = value
+      value = container
+      container = last.container
+      key = last.key
+      state = last.state
+    }
+  },
+  '(': {
+    [go] () {
+      stack.push({state: good})
+      container = []
+      state = firstArrayValue
+    },
+    [dictValue] () {
+      stack.push({
+        container,
+        key,
+        state: dictSeparator
+      })
+    },
+    [firstArrayValue] () {
+      stack.push({
+        container,
+        state: arraySeparator
+      })
+    },
+    [arrayValue] () {
+      stack.push({
+        container,
+        state: arraySeparator
+      })
+    }
+  },
+  ')': {
+    [firstArrayValue] () {
+      const last = stack.pop()
+      value = container
+      container = last.container
+      key = last.key
+      state = last.state
+    },
+    [arraySeparator] () {
+      const last = stack.pop()
+      container.push(value)
+      value = container
+      container = last.container
+      key = last.key
+      state = last.state
+    }
+  },
+  '=': {
+    [equals] () {
+      // TODO perhaps throw on duplicate key
+      state = dictValue
+    }
+  },
+  ';': {
+    [dictSeparator] () {
+      container[key] = value
+      state = dictKey
+    }
+  },
+  ',': {
+    [arraySeparator] () {
+      container.push(value)
+      state = arrayValue
+    }
+  }
+}
+
+module.exports = function parse (plist) {
+  state = go
+  stack = []
+  container = key = value = null
+  const invalid = new SyntaxError('excuse me, that is not valid')
+  try {
+    while (true) {
+      let result
+      result = tokens.exec(plist)
+      if (!result) {
+        break
+      }
+      const [capture, token, string] = result
+      if (token) {
+        action[token][state]()
+      } else {
+        value = escape(string)
+        stringAction[state]()
+      }
+      plist = plist.slice(capture.length)
+    }
+  } catch (error) {
+    throw invalid
+  }
+
+  if (state !== good) throw invalid
+
+  return value
+}

index.js

@@ -0,0 +1,4 @@
+module.exports = {
+  parse: require('./code/parse')
+  // stringify: require('./code/stringify')
+}