import md5, os, osproc, parseopt2, strutils, parsecfg, streams

# This is a little utility program for handling large files
# in git repositories. Its inspired by git-fat and s3annex
# but doesn't rely on S3 for storage.
#
# Use "fat d mybigfile" to deflate it before commit.
# Use "fat i mybigfile" to inflate it back to original size.
#
# When deflated the file only has an md5sum string inside it.
#
# The file is copied over into:
#  <homedir>/fatstore/<originalfilename>-<md5sum>

var fatstore, remoteFatstore: string


# Load fatstore.conf file, overkill for now but...
proc parseConfFile(filename: string) =
  echo filename
  var f = newFileStream(filename, fmRead)
  if f != nil:
    var p: CfgParser
    open(p, f, filename)
    while true:
      var e = next(p)
      case e.kind
      of cfgEof: 
        break
      of cfgSectionStart:
        continue # Ignore
      of cfgKeyValuePair:
        if e.key == "remote":
          remoteFatstore = e.value
        else:
          quit("Unknown configuration: " & e.key)
      of cfgOption:
        quit("Unknown configuration: " & e.key)
      of cfgError:
        quit("Parsing " & filename & ": " & e.msg)
    close(p)


# Upload a file to the remote master fatstore
proc uploadFile(fatfilename: string) =
  if remoteFatstore.isNil:
    echo("Remote fatstore not set in configuration file, not uploading content:\n\t" & fatfilename)
    return
  let errorCode = execCmd("rsync -a " & fatstore / fatfilename & " " & remoteFatstore)
  if errorCode != 0: quit("Something went wrong uploading content to " & remoteFatstore, 2)
  
# Download a file to the remote master fatstore
proc downloadFile(fatfilename: string) =
  if remoteFatstore.isNil:
    quit("Remote fatstore not set in configuration file, can not download content:\n\t" & fatfilename)
  let errorCode = execCmd("rsync -a " & remoteFatstore / fatfilename & " " & fatstore / "")
  if errorCode != 0: quit("Something went wrong downloading " & fatfilename & " from " & remoteFatstore, 3)


# Copy content to fatstore, no upload yet.
proc copyToFatstore(filename, fatfilename: string) =
  if not existsFile(fatstore / fatfilename):
    copyFile(filename, fatstore / fatfilename)
    uploadFile(fatfilename)

# Copy content from fatstore, and downloading first if needed
proc copyFromFatstore(fatfilename, filename: string) =
  if not existsFile(fatstore / fatfilename):
    downloadFile(fatfilename)
  copyFile(fatstore / fatfilename, filename)

    
# Copy original file to fatstore and replace with hash stub in git.
proc deflate(filename: string) =
  let content = readFile(filename)
  if content[0..4] == "hash:":
    quit("File is already deflated, ignored.", 5)
  let hash = getMD5(content)
  let fatfilename = filename & "-" & hash
  copyToFatstore(filename, fatfilename)
  writeFile(filename, "hash:" & fatfilename)

# Parse out hash from hash stub and copy back original content from fatstore.
proc inflate(filename: string) =
  var hashfile: File
  if not open(hashfile, filename):
    quit("Could not open file: " & filename, 4)
  let hashline = split(string(readLine(hashfile)), {':'})
  if hashline[0] == "hash":
    let fatfilename = hashline[1]
    #removeFile(filename)
    copyFromFatstore(fatfilename, filename)
  else:
    quit("File is not a fat file.", 5)


################################ main #####################################

# Hardwired to "fatstore" directory in home dir.
fatstore = getHomeDir() / "fatstore"

# Make sure we have the dir, or create it.
try:
  if not existsDir(fatstore): createDir(fatstore)
except:
  quit("Could not create " & fatstore & " directory.", 1)


# Parse configuration if it exists
parseConfFile(fatstore / "fatstore.conf")

# Only a command and a path as argument
let argv = commandLineParams()
let command = argv[0]
let filename = argv[1]


# Do the deed
if command == "d" or command == "deflate":
  deflate(filename)
elif command == "i" or command == "inflate":
  inflate(filename)
else:
  quit("Unknown command, only (d)eflate or (i)inflate are valid.", 6)

# All good
quit(0)