#!/bin/sh
#
# ShellFlow: the simplest workflow orchestrator in under
# 20 SLOC of POSIX shell, using Unix pipelines
#
# Usage: echo some_input | /path/to/flow.sh /path/to/workflow
#
# Exposes the following variables to workflows and tasks:
# - SFLIB - resolved path to this file
# - WFDIR - directory of the workflow
#
# Also exposes the debugout function to output to stderr
#
# Typical workflow script structure: ./task1 | ./task2 | ./task3 ...
# (the workflow directory becomes the current working directory)
#
# Data format: workflow name, tab character, all other input
#
# Typical task script structure (if shell-based): 
# #!/bin/sh
# . $SFLIB # source the library part of the script
# do_task() { # accepts workflow name into $1 and all input into $2
#   # your actions here
# }
# run-task
#
# You can call different workflows from inside tasks by referring to
# this very script using the $SFLIB environment variable or by calling
# the sfrun function
#
# Created by Luxferre in 2025, released into public domain

# ShellFlow task function library

# print to stderr
debugout() { printf '%s\n' "$*" >&2; }

# format the message and print to stdout
flowout() { printf '%s\t%s' "$1" "$2"; }

# use this in all task definitions
run-task() {
  input="$(cat)"
  wf="$(printf '%s' "$input" | cut -f 1)"
  body="$(printf '%s' "$input" | cut -f 2-)"
  flowout "$wf" "$(do_task "$wf" "$body")"
}

# ShellFlow entry point

sfrun() {
  SFLIB="$(readlink -f "$0")"
  wfbase="$(basename "$1")"
  WFDIR="$(readlink -f $(dirname -- "$1"))"
  cd "$WFDIR"
  debugout "Starting workflow $wfbase..."
  flowout $wfbase "$(cat)" | SFLIB="$SFLIB" WFDIR="$WFDIR" $SHELL $wfbase | cut -f 2-
}

[ "$(basename "$0")" == "flow.sh" ] && sfrun $*