-- local db = require("solvitdb")
local db = {}
local fs = require("filesystem")
local json = require("json")
local dbpath = "/ag2/testdb.json"
function db.create()
  local handle = fs.open(dbpath,"w")
  handle:write("{}")
  handle:close()
end
function db.readJSON()
  local handle = fs.open(dbpath,"r")
  local content = ""
  while true do
    local s = handle:read(math.huge or math.maxinteger)
    if not s then break end
    content=content..s
  end
  handle:close()
  return content
end
function db.get(pack)
  local dbc = json.decode(db.readJSON())
  return dbc[pack]
end
function db.set(pack,info)
  local dbc = json.decode(db.readJSON())
  dbc[pack]=info
  local handle = fs.open(dbpath,"w")
  handle:write(json.encode(dbc))
  handle:close()
end
function db.remove(pack)
  local dbc = json.decode(db.readJSON())
  dbc[pack]=nil
  local handle = fs.open(dbpath,"w")
  handle:write(json.encode(dbc))
  handle:close()
end

local avs = {}
function avs.splitSingular(s)
  local result = {}
  for str in string.gmatch(s, "([^.]+)") do
    table.insert(result,tonumber(str) or -1)
  end
  return result
end

function avs.parse(pack)
  if not string.find(pack,"=") then
    return {pack}
  end
  local idx=pack:find("=")
  local name=pack:sub(1,idx-1)
  local verstr=pack:sub(idx+1)
  if string.find(verstr,"-") then
    idx=verstr:find("-")
    verstr={verstr:sub(1,idx-1),verstr:sub(idx+1)}
  else
    verstr={verstr}
  end
  for i=1,#verstr do
    verstr[i]=avs.splitSingular(verstr[i])
  end
  if #verstr>1 then
    for i=1,3 do
      verstr[1][i]=math.max(verstr[1][i],0)
    end
  end
  return {name,verstr}
end

function avs.serializeSingle(ver)
  local ver2 = table.copy(ver)
  for i=1,3 do
    if ver2[i]==-1 then
      ver2[i]="*"
    else
      ver2[i]=tostring(ver2[i])
    end
  end
  return ver2[1].."."..ver2[2].."."..ver2[3]
end

function avs.serializeVersion(ver)
  local singles = {}
  for i=1,#ver do
    table.insert(singles,avs.serializeSingle(ver[i]))
  end
  if singles[1]==singles[2] then
    singles={singles[1]}
  end
  local out=""
  for i=1,#singles do
    out=out..singles[i]
    if i~=#singles then
      out=out.."-"
    end
  end
  return out
end

function avs.serializePack(pack)
  if #pack==1 then
    return pack[1]
  end
  return pack[1].."="..avs.serializeVersion(pack[2])
end

function avs.singleGreater(ver1,ver2)
  for i=1,3 do
    if ver1[i]~=ver2[i] then
      if ver1[i]==-1 or ver1[i]>ver2[i] then
        return true
      end
      if ver2[i]==-1 or ver2[i]>ver1[i] then
        return false
      end
    end
  end
  return false
end

function avs.singleLesser(ver1,ver2)
  return avs.singleGreater(ver2,ver1)
end

function avs.singleMin(ver1,ver2)
  return avs.singleLesser(ver1,ver2) and ver1 or ver2
end

function avs.singleMax(ver1,ver2)
  return avs.singleGreater(ver1,ver2) and ver1 or ver2
end

function avs.compatibleRange(vers)
  for i=1,#vers do
    if type(vers[i])=="string" then vers[i]=avs.parse(vers[i])[2] end
    if #vers[i]==1 then vers[i]={vers[i][1],vers[i][1]} end
  end
  local range = vers[1]
  for i=2,#vers do
    range[1]=avs.singleMax(range[1],vers[i][1])
    range[2]=avs.singleMin(range[2],vers[i][2])
  end
  if avs.singleGreater(range[1],range[2]) then
    return nil
  end
  return range
end

local function packageInArray(pack,arr)
  for i=1,#arr do
    if arr[i][1]==pack[1] then -- TODO: check for compatible package version
      return true
    end
  end
  return false
end

local function startTransaction()
  if not fs.exists(dbpath) then
    db.create()
  end

  local installIncomplete = false
  local removeIncomplete = false

  local packInfo = {}
  local ins = {}
  local rem = {}
  local transaction = {}
  function transaction.install(name)
    table.insert(ins,avs.parse(name))
    installIncomplete = true
  end
  function transaction.remove(name)
    table.insert(rem,avs.parse(name))
    removeIncomplete = true
  end
  function transaction.autoRemove()
  end
  function transaction.update(name)
  end
  function transaction.updateAll(name)
  end
  function transaction.addInfo(name,info)
    packInfo[name]=info
    -- print(require("serialize").table(packInfo))
  end

  local function getPackInfo(pack)
    return packInfo[avs.serializePack(pack)]
  end
  local function finalizeInstall(settings)
    installIncomplete=false
    -- find missing package information
    local missing = {}
    for i=1,#ins do
      if getPackInfo(ins[i])==nil then
        table.insert(missing,avs.serializePack(ins[i]))
      end
    end
    if #missing>0 then
      return false,missing
    end
    -- find dependencies
    local i=1
    while i<=#ins do
      local deps = getPackInfo(ins[i]).dependencies
      if deps and #deps>=1 then
        for j=1,#deps do
          local dep = avs.parse(deps[j])
          if (not packageInArray(dep,ins)) and type(db.get(dep[1]))=="nil" then
            installIncomplete=true
            table.insert(ins,j,dep)
          end
        end
        i=i+#deps
      end
      i=i+1
    end
  end
  local function finalizeRemove(settings)
    removeIncomplete=false
    -- filter to only have packages in the database
    local i=1
    while i<=#rem do
      local dat = db.get(rem[i][1])
      if not dat then
        table.remove(rem,i)
      else
        packInfo[avs.serializePack(rem[i])]=dat
        i=i+1
      end
    end
    -- look for dependencies if settings.autoremove is on
    if settings.autoremove then
      i=1
      while i<=#rem do
        local deps = getPackInfo(rem[i]).dependencies
        if deps and #deps>=1 then
          for j=1,#deps do
            local dep = avs.parse(deps[j])
            local depdat = packInfo[deps[j]]
            if not depdat then
              depdat = db.get(deps[j])
              packInfo[deps[j]]=depdat
            end
            if (not packageInArray(dep,rem)) and type(db.get(dep[1]))~="nil" and (#depdat.reverseDependencies==1 and depdat.reverseDependencies[1]==avs.serializePack(rem[i])) then
              removeIncomplete=true
              table.insert(rem,j,dep)
            end
          end
          i=i+#deps
        end
        i=i+1
      end
    end
  end
  function transaction.finalize(settings)
    while installIncomplete or removeIncomplete do
      while installIncomplete do
        local out = {finalizeInstall(settings)}
        if out[1]==false then return table.unpack(out) end
      end
      while removeIncomplete do
        local out = {finalizeRemove(settings)}
        if out[1]==false then return table.unpack(out) end
      end
    end

    local install = {}
    local remove = {}
    for i=1,#ins do
      table.insert(install,avs.serializePack(ins[i]))
    end
    for i=1,#rem do
      table.insert(remove,avs.serializePack(rem[i]))
    end
    return true, {install=install,remove=remove}

    -- return "true, {["install"] = {"dep1", "package1", "package2"}, ["remove"] = {"package3"}}" on success
    -- return "false, {"dep1"}" when not enough data
    -- return "false, "[verbose string]"" when conflict found
    -- TODO: implement storing removal
    -- TODO: implement storing reverse dependency removal
    -- TODO: implement reverse dependency conflict when removing (don't conflict if the reverse dependencies are already in the list!)
    -- TODO: handle same constant AVS
    -- TODO: handle different constant AVS conflict
    -- TODO: handle same range AVS
    -- TODO: handle different intercompatible 1.*.* range AVS
    -- TODO: handle different incompatible 1.*.* range AVS
    -- TODO: handle different intercompatible 1.*.*-2.*.* range AVS
    -- TODO: handle different incompatible 1.*.*-2.*.* range AVS
    -- TODO: handle conflicts from package info
    -- TODO: handle reverse conflicts from another package's info
    -- TODO: handle update of a single package with no dependencies
    -- TODO: handle update of a single package with dependencies that don't need updating
    -- TODO: handle update of a single package with dependencies that need updating
    -- TODO: handle update of a single package that has a set dependency version changed
    -- TODO: handle updating all packages in the database
  end
  function transaction.store()
    -- directly set
    for _,pack in ipairs(ins) do
      if packInfo[pack[1]] then
        local info = table.copy(packInfo[pack[1]])
        info.version=pack[2]
        db.set(pack[1],info)
      end
    end
    -- set reverse dependencies
    for _,pack in pairs(ins) do
      local i = pack[1]
      local v = packInfo[i]
      if v and v.dependencies then
        for _,dep in ipairs(v.dependencies) do
          local dat = db.get(dep)
          if not dat then goto continue end
          if type(dat.reverseDependencies)~="table" then
            dat.reverseDependencies={}
          end
          table.insert(dat.reverseDependencies,i)
          db.set(dep,dat)
          ::continue::
        end
      end
    end
  end
  return transaction
end

return { avs=avs,startTransaction=startTransaction }