#! /usr/bin/awk -f
#
# ledger balance calculator
#
# usage:
#   [colorize=false] [scale=N] //ledger/lib/balance LEDGER_FILE...
#   [colorize=false] [scale=N] //ledger/lib/balance < LEDGER_FILE
#
# description:
#   The ledger balance calculator computes the balance of each account it
#   encounters in the provided ledger files.
#
# example:
#   //ledger/lib/balance < //cholerab/ledger-spec.markdown
#
# see also:
#   //cholerab/ledger-spec.markdown (ledger file format)
#

BEGIN {
  colorize = ENVIRON["colorize"] == "" || ENVIRON["colorize"] == "true"
  # TODO use bc for arbitrary precision arithmetic
  scale = ENVIRON["scale"]
}

/^[[:space:]]*[0-9]+-[0-9][0-9]-[0-9][0-9]/{
  tx($2, $3, $4, $5)
}

END {
  display_accounts()
}

function tx (dst, src, amt, u) {
  withdraw(src, amt, u)
  deposit(dst, amt, u)
}

function deposit (name, amt, u) {
  accounts[name][u] += amt
}

function withdraw (name, amt, u) {
  accounts[name][u] -= amt
}

function display_accounts() {
  max_name_len = 0
  for (name in accounts) {
    if (length(name) > max_name_len) {
      max_name_len = length(name)
    }
  }

  max_balance_len = 0
  for (name in accounts) {
    for (u in accounts[name]) {
      n = length(int(accounts[name][u]))
      if (n > max_balance_len) {
        max_balance_len = n
      }
    }
  }
  if (scale > 0) {
    max_balance_len += length(".") + scale
  }

  for (name in accounts) {
    for (u in accounts[name]) {
      balance = accounts[name][u]
      if (balance == 0) {
        continue
      }

      fmt = "NAME BALANCE UNIT\n"

      if (colorize) {
        sub("BALANCE", "[" (balance < 0 ? 31 : 32) "m&", fmt)
      }

      sub("NAME", "%-" max_name_len "s", fmt)
      sub("BALANCE", "%" max_balance_len "." scale "f", fmt)
      sub("UNIT", "%s", fmt)

      printf fmt, name, balance, u
    }
  }
}