# SPDX-FileCopyrightText: 2021 Nixpkgs/NixOS contributors
## Custom Nim builder for Nixpkgs.

import std/[os, osproc, parseutils, sequtils, streams, strutils]

proc findNimbleFile(): string =
  ## Copied from Nimble.
  ## Copyright (c) 2015, Dominik Picheta
  ## BSD3
  let dir = getCurrentDir()
  result = ""
  var hits = 0
  for kind, path in walkDir(dir):
    if kind in {pcFile, pcLinkToFile}:
      let ext = path.splitFile.ext
      if ext == ".nimble":
        result = path
        inc hits
  if hits >= 2:
    quit("Only one .nimble file should be present in " & dir)
  elif hits == 0:
    quit("Could not find a file with a .nimble extension in " & dir)

proc getEnvBool(key: string; default = false): bool =
  ## Parse a boolean environmental variable.
  let val = getEnv(key)
  if val == "": default
  else: parseBool(val)

proc getNimbleFilePath(): string =
  ## Get the Nimble file for the current package.
  if existsEnv"nimbleFile":
    getEnv"nimbleFile"
  else:
    findNimbleFile()

proc getNimbleValue(filePath, key: string; default = ""): string =
  ## Extract a string value from the Nimble file at ``filePath``.
  var
    fs = newFileStream(filePath, fmRead)
    line: string
  if fs.isNil:
    quit("could not open " & filePath)
  while fs.readline(line):
    if line.startsWith(key):
      var i = key.len
      i.inc skipWhile(line, Whitespace, i)
      if line[i] == '=':
        inc i
        i.inc skipWhile(line, Whitespace, i)
        discard parseUntil(line, result, Newlines, i)
        if result.len > 0 and result[0] == '"':
          result = result.unescape
        return
  default

proc getNimbleValues(filePath, key: string): seq[string] =
  ## Extract a string sequence from the Nimble file at ``filePath``.
  var gunk = getNimbleValue(filePath, key)
  result = gunk.strip(chars = {'@', '[', ']'}).split(',')
  if result == @[""]: reset result
  apply(result) do (s: var string):
    s = s.strip()
    if s.len > 0 and s[0] == '"':
      s = s.unescape()

proc getOutputDir(name: string): string =
  ## Return the output directory for output `name`.
  ## If `name` is not a valid output then the first output
  ## is returned as a default.
  let outputs = splitWhitespace getEnv("outputs")
  doAssert(outputs.len > 0)
  if outputs.contains name:
    result = getEnv(name)
  if result == "":
    result = getEnv("out")
  if result == "":
    result = getEnv(outputs[0], "/dev/null")

proc configurePhase*() =
  ## Generate "config.nims" which will be read by the Nim
  ## compiler during later phases.
  const configFilePath = "config.nims"
  echo "generating ", configFilePath
  let
    nf = getNimbleFilePath()
    mode =
      if fileExists configFilePath: fmAppend
      else: fmWrite
  var cfg = newFileStream(configFilePath, mode)
  proc switch(key, val: string) =
    cfg.writeLine("switch(", key.escape, ",", val.escape, ")")
  switch("backend", nf.getNimbleValue("backend", "c"))
  switch("nimcache", getEnv("NIX_BUILD_TOP", ".") / "nimcache")
  if getEnvBool("nimRelease", true):
    switch("define", "release")
  for def in getEnv("nimDefines").split:
    if def != "":
      switch("define", def)
  for input in getEnv("NIX_NIM_BUILD_INPUTS").split:
    if input != "":
      for nimbleFile in walkFiles(input / "*.nimble"):
        let inputSrc = normalizedPath(
            input / nimbleFile.getNimbleValue("srcDir", "."))
        echo "found nimble input ", inputSrc
        switch("path", inputSrc)
  close(cfg)

proc buildPhase*() =
  ## Build the programs listed in the Nimble file and
  ## optionally some documentation.
  var cmds: seq[string]
  proc before(idx: int) =
    echo "build job ", idx, ": ", cmds[idx]
  let
    nf = getNimbleFilePath()
    bins = nf.getNimbleValues("bin")
    srcDir = nf.getNimbleValue("srcDir", ".")
    binDir = getOutputDir("bin") / "bin"
  if bins != @[]:
    for bin in bins:
      cmds.add("nim compile $# --outdir:$# $#" %
          [getenv"nimFlags", binDir, normalizedPath(srcDir / bin)])
  if getEnvBool"nimDoc":
    echo "generating documentation"
    let docDir = getOutputDir("doc") / "doc"
    for path in walkFiles(srcDir / "*.nim"):
      cmds.add("nim doc --outdir:$# $#" % [docDir, path])
  if cmds.len > 0:
    let err = execProcesses(
      cmds, n = 1,
      beforeRunEvent = before)
    if err != 0: quit("build phase failed", err)

proc installPhase*() =
  ## Install the Nim sources if ``nimBinOnly`` is not
  ## set in the environment.
  if not getEnvBool"nimBinOnly":
    let
      nf = getNimbleFilePath()
      srcDir = nf.getNimbleValue("srcDir", ".")
      devDir = getOutputDir "dev"
    echo "Install ", srcDir, " to ", devDir
    copyDir(normalizedPath(srcDir), normalizedPath(devDir / srcDir))
    copyFile(nf, devDir / nf.extractFilename)

proc checkPhase*() =
  ## Build and run the tests in ``tests``.
  var cmds: seq[string]
  proc before(idx: int) =
    echo "check job ", idx, ": ", cmds[idx]
  for path in walkPattern("tests/t*.nim"):
    cmds.add("nim r $#" % [path])
  let err = execProcesses(
    cmds, n = 1,
    beforeRunEvent = before)
  if err != 0: quit("check phase failed", err)

when isMainModule:
  import std/parseopt
  var phase: string

  for kind, key, val in getopt():
    case kind
    of cmdLongOption:
      case key.toLowerAscii
      of "phase":
        if phase != "": quit("only a single phase may be specified")
        phase = val
      else: quit("unhandled argument " & key)
    of cmdEnd: discard
    else: quit("unhandled argument " & key)

  case phase
  of "configure": configurePhase()
  of "build": buildPhase()
  of "install": installPhase()
  of "check": checkPhase()
  else: quit("unhandled phase " & phase)