--- Tokenomics.
-- @module tokenomics

local tokenomics = {
    name = "Tokenomics",
    slug = "tokenomics",
    desc = "A simple library for token economics",
    hide = true;
}

tokenomics.data = {
   result = nil
}

--- Config for module 
-- @field token_variables the data that goes into the token
-- @field token_slug A no-spaces slug for the token
-- @field initial_treasury Quantity in org treasury
-- @field negative_spend Boolean: can users spend negative tokens? (for mutual credit)
-- @field balances Table of user balances
tokenomics.config = {
   approval_module = false,
   token_slug = "token",
   token_variables = {
      treasury = 0,
      negative_spend = true,
      balances = {}
   }
}

--- Initiate function: creates a token in an org.
-- Set up the token data structure.
-- Create an org treasury
-- @function tokenomics:initiate
-- @param result (optional) Callback if this module is embedded in other modules
function tokenomics:initiate(result)
   -- TODO need to create a series of interactions to get the info from users
   self.data.result = result
   if self.org.tokens and self.org.tokens[slug] then
      modpol.interactions.message(
         self.initiator, "Token slug taken, aborting")
      self.org:delete_process(self.id)
   else
      self:call_module(
         self.config.approval_module,
         self.initiator,
         {
            prompt = "Create token " ..
               self.config.token_slug .. "?"
         },
         function()
            modpol.interactions.message_org(
               self.initiator, self.org.id,
               "Creating token " ..
               self.config.token_slug)
            self:create_token()
         end
      )
   end
end


--- Create token
-- @function tokenomics:create_token
function tokenomics:create_token()
   if not self.org.tokens then self.org.tokens = {} end
   self.org.tokens[self.config.token_slug] =
      self.config.token_variables
   self.org:record("Created token "..self.config.token_slug,
                   self.slug)
   modpol.interactions.message_org(
      self.initiator, self.org.id,
      "Created token "..self.config.token_slug)
   if self.data.result then self.data.result() end
   -- call this wherever process might end:
   self.org:delete_process(self.id)
end

-----------------------------------------
-- Utility functions
-- all need to account for the fact that some users may not yet have balances
-- all need to write to persistent data
-- amount can be positive or negative (except transfer)

--- Returns balance.
-- If no user, get treasury balance
-- @function tokenomics.balance
-- @param org Name (string) or id (num)
-- @param token Slug (string)
-- @param user Name (string)
function tokenomics.balance(org, token, user)
   local this_org = modpol.orgs.get_org(org)
   if not this_org[token] then return nil, "Token not found" end
   if not user then
      return this_org[token].treasury
   end
   if not this_org[user] then
      return nil, "User not found"
   else
      local user_balance = this_org[token].balances[user]
      if user_balance then
         return user_balance
      else
         return 0
      end
   end
end

--- Change balance
-- @function tokenomics.change_balance
-- @param org Org name (string) or id (number)
-- @param token Token slug (string)
-- @param user
-- @param amount
function tokenomics.change_balance(org, token, user, amount)
   local this_org = modpol.orgs.get_org(org)
   if not this_org then
      return nil, "Cannot change balance: Org not found"
   elseif not this_org.tokens then
      return nil, "Cannot change balance: no tokens found"
   elseif not this_org.tokens[token] then
      return nil, "Cannot change balance: token not found"
   elseif not this_org.members[user] then
      return nil, "Cannot change balance: user not in org"
   elseif not tonumber(amount) then
      return nil, "Cannot change balance: invalid amount"
   else
      local old_balance = this_org.tokens[token].balances[user]
      if not old_balance then old_balance = 0 end
      local new_balance = old_balance + amount
      this_org.tokens[token].balances[user] = new_balance
      local msg = "Your balance of token "..token..
         " changed from "..old_balance.." to "..new_balance
      modpol.interactions.message(user, msg)
      self.org:record(
         "Changed token balance for "..user,self.slug)
   end
end

--- Transfer tokens from a sender to recipient
-- @function tokenomics.transfer
-- @param org
-- @param token
-- @param sender
-- @param recipient
-- @param amount Positive number
function tokenomics.transfer(org, token, sender, recipient, amount)
   local sender_balance = tokenomics.balance(org, token, sender)
   local recipient_balance = tokenomics.balance(org, token, recipient)
   if not sender_balance or recipient_balance then
      return nil, "Transfer failed, user not found"
   else
      sender_balance = sender_balance - amount
      recipient_balance = recipient_balance + amount
      local neg_spend = modpol.orgs.get_org(org).tokens[token].negative_spend
      if sender_balance < 0 and not neg_spend then
         return nil, "Transfer failed, negative spend not allowed"
      else
         tokenomics.change_balance(
            org, token, sender, sender_balance)
         tokenomics.change_balance(
            org, token, recipient, recipient_balance)
         return "Transfer complete"
      end
   end
end

--- Transfer from treasury
-- @function tokenomics.treasury_transfer
-- @param org
-- @param token
-- @param recipient
-- @param amount Can be positive or negative, assumes flow from treasury to recipient
function tokenomics.treasury_transfer(org, token, recipient, amount)
   local this_org = modpol.orgs.get_org(org)
   if not this_org then
      return nil, "Cannot transfer treasury: Org not found"
   elseif not this_org.tokens then
      return nil, "Cannot transfer treasury: no tokens found"
   elseif not this_org.tokens[token] then
      return nil, "Cannot transfer treasury: token not found"
   elseif not this_org.members[user] then
      return nil, "Cannot transfer treasury: user not in org"
   elseif not tonumber(amount) then
      return nil, "Cannot change balance: invalid amount"
   else
      local new_treasury = this_org.tokens[token].treasury - amount
      local new_recipient_balance = tokenomics.balance(org, token, recipient) + amount
      if new_treasury < 0 and not this_org.tokens[token].negative_spend then
         return nil, "Transfer failed, negative spend not allowed"
      elseif new_recipient_balance < 0 and not this_org.tokens[token].negative_spend then
         return nil, "Transfer failed, negative spend not allowed"
      else
         this_org.tokens[token].treasury = new_treasury
         self.org:record("Treasury payment",self.slug)
         tokenomics.change_balance(org, token, recipient, amount)
      end
   end
end

--- Creates new tokens in the org treasury
-- @function tokenomics.issue
-- @param org
-- @param token
-- @param amount
function tokenomics.issue(org, token, amount)
   local this_org = modpol.orgs.get_org(org)
   if not this_org then
      return nil, "Cannot transfer treasury: Org not found"
   elseif not this_org.tokens then
      return nil, "Cannot transfer treasury: no tokens found"
   elseif not this_org.tokens[token] then
      return nil, "Cannot transfer treasury: token not found"
   elseif not tonumber(amount) then
      return nil, "Cannot change balance: invalid amount"
   else
      this_org.tokens[token].treasury =
         this_org.tokens[token].treasury + amount
      self.org:record("Issued tokes to treasury","tokenomics")
   end
end

------------------------------------------

modpol.modules.tokenomics = tokenomics