#
# Implements semantic date parsing from strings such as "today", "yesterday", "last week"
#
class SemanticDate
  # Define a set of parsers to handle semantic date specifications.
  @parsers = [
    match: /^(last|past)[ _\-]?minute$/i
    func: (now) ->
      start: new Date(now - 60000)
      end: now
  ,
    match: /^(last|past)[ _\-]?hour$/i
    func: (now) ->
      start: new Date(now - 3600000)
      end: now
  ,
    match: /^(last|past)[ _\-]?24(h| hours)$/i
    func: (now) ->
      start: new Date(now - 86400000)
      end: now
  ,
    match: /^yesterday$/i
    func: (now) ->
      start: new Date(new Date(now.getFullYear(), now.getMonth(), now.getDate()) - 86400000)
      end: new Date(now.getFullYear(), now.getMonth(), now.getDate())
  ,
    match: /^last[ _\-]?week$/i
    func: (now) ->
      start: new Date(new Date(now.getFullYear(), now.getMonth(), now.getDate()) - now.getDay() * 86400000 - 604800000)
      end: new Date(new Date(now.getFullYear(), now.getMonth(), now.getDate()) - now.getDay() * 86400000)
  ,
    match: /^past[ _\-]?week$/i
    func: (now) ->
      start: new Date(now - 604800000)
      end: now
  ,
    match: /^last[ _\-]?month$/i
    func: (now) ->
      month = now.getMonth() - 1
      month = 11  if month < 0
      start: new Date(now.getFullYear(), month, 1)
      end: new Date(now.getFullYear(), now.getMonth(), 1)
  ,
    match: /^past[ _\-]?month$/i
    func: (now) ->
      start: new Date(now - 2592000000)
      end: now
  ,
    match: /^last[ _\-]?year$/i
    func: (now) ->
      start: new Date(now.getFullYear() - 1, 0, 1)
      end: new Date(now.getFullYear(), 0, 1)
  ,
    match: /^past[ _\-]?year$/i
    func: (now) ->
      start: new Date(now - 31536000000)
      end: now
  ,
    match: /^today$/i
    func: (now) ->
      start: new Date(now.getFullYear(), now.getMonth(), now.getDate())
      end: now
  ,
    match: /^this[ _\-]?week$/i
    func: (now) ->
      start: new Date(new Date(now.getFullYear(), now.getMonth(), now.getDate()) - now.getDay() * 86400000)
      end: now
  ,
    match: /^this[ _\-]?month$/i
    func: (now) ->
      start: new Date(now.getFullYear(), now.getMonth(), 1)
      end: now
  ,
    match: /^this[ _\-]?year$/i
    func: (now) ->
      start: new Date(now.getFullYear(), 0, 1)
      end: now
  ,
    match: /^since[ _\-]?1970$/i
    func: (now) ->
      start: new Date(1970, 0, 1)
      end: now
  ]

  # Perform validation of the given semantic date string. Returns true if the string is supported, false otherwise.
  @validate: (str) ->
    for p in @parsers
      return true if str.match p.match
    return false

  # Convert the given semantic date string to an object with start and end Date objects.
  @convert: (str, now) ->
    unless now
      now = new Date()
    for p in @parsers
      if str.match p.match
        return p.func(now)


#
# Exports, browser compatible
#
if typeof exports isnt "undefined" and exports isnt null
  module.exports = SemanticDate
else
  window.SemanticDate = SemanticDate