## Utility API for Nim package managers.
## (c) 2021 Andreas Rumpf

import std / strutils
import ".." / ".." / compiler / [ast, idents, msgs, syntaxes, options, pathutils]

type
  NimbleFileInfo* = object
    requires*: seq[string]
    srcDir*: string
    tasks*: seq[(string, string)]

proc extract(n: PNode; conf: ConfigRef; result: var NimbleFileInfo) =
  case n.kind
  of nkStmtList, nkStmtListExpr:
    for child in n:
      extract(child, conf, result)
  of nkCallKinds:
    if n[0].kind == nkIdent:
      case n[0].ident.s
      of "requires":
        for i in 1..<n.len:
          var ch = n[i]
          while ch.kind in {nkStmtListExpr, nkStmtList} and ch.len > 0: ch = ch.lastSon
          if ch.kind in {nkStrLit..nkTripleStrLit}:
            result.requires.add ch.strVal
          else:
            localError(conf, ch.info, "'requires' takes string literals")
      of "task":
        if n.len >= 3 and n[1].kind == nkIdent and n[2].kind in {nkStrLit..nkTripleStrLit}:
          result.tasks.add((n[1].ident.s, n[2].strVal))
      else: discard
  of nkAsgn, nkFastAsgn:
    if n[0].kind == nkIdent and cmpIgnoreCase(n[0].ident.s, "srcDir") == 0:
      if n[1].kind in {nkStrLit..nkTripleStrLit}:
        result.srcDir = n[1].strVal
      else:
        localError(conf, n[1].info, "assignments to 'srcDir' must be string literals")
  else:
    discard

proc extractRequiresInfo*(nimbleFile: string): NimbleFileInfo =
  ## Extract the `requires` information from a Nimble file. This does **not**
  ## evaluate the Nimble file. Errors are produced on stderr/stdout and are
  ## formatted as the Nim compiler does it. The parser uses the Nim compiler
  ## as an API. The result can be empty, this is not an error, only parsing
  ## errors are reported.
  var conf = newConfigRef()
  conf.foreignPackageNotes = {}
  conf.notes = {}
  conf.mainPackageNotes = {}

  let fileIdx = fileInfoIdx(conf, AbsoluteFile nimbleFile)
  var parser: Parser
  if setupParser(parser, fileIdx, newIdentCache(), conf):
    extract(parseAll(parser), conf, result)
    closeParser(parser)

const Operators* = {'<', '>', '=', '&', '@', '!', '^'}

proc token(s: string; idx: int; lit: var string): int =
  var i = idx
  if i >= s.len: return i
  while s[i] in Whitespace: inc(i)
  case s[i]
  of Letters, '#':
    lit.add s[i]
    inc i
    while i < s.len and s[i] notin (Whitespace + {'@', '#'}):
      lit.add s[i]
      inc i
  of '0'..'9':
    while i < s.len and s[i] in {'0'..'9', '.'}:
      lit.add s[i]
      inc i
  of '"':
    inc i
    while i < s.len and s[i] != '"':
      lit.add s[i]
      inc i
    inc i
  of Operators:
    while i < s.len and s[i] in Operators:
      lit.add s[i]
      inc i
  else:
    lit.add s[i]
    inc i
  result = i

iterator tokenizeRequires*(s: string): string =
  var start = 0
  var tok = ""
  while start < s.len:
    tok.setLen 0
    start = token(s, start, tok)
    yield tok

when isMainModule:
  for x in tokenizeRequires("jester@#head >= 1.5 & <= 1.8"):
    echo x