name = "env_path_builder"
category = "environment"
mode = "convert"
description = """
Read directory paths from stdin, one per line.
Append each to the MYPATH environment variable (colon-separated), skipping duplicates.
The initial value of MYPATH is provided via the environment (may be empty).
Print the final value of MYPATH to stdout.
"""

bash_source = """
#!/bin/bash
while IFS= read -r dir || [[ -n "$dir" ]]; do
    if [[ -z "$MYPATH" ]]; then
        export MYPATH="$dir"
    elif [[ ":$MYPATH:" != *":$dir:"* ]]; then
        export MYPATH="$MYPATH:$dir"
    fi
done
echo "$MYPATH"
"""

[[test_cases]]
stdin = """/usr/local/bin
/usr/bin
/usr/local/bin
/opt/bin"""
expected_stdout = "/usr/local/bin:/usr/bin:/opt/bin"
env = { "MYPATH" = "" }

[[test_cases]]
stdin = """/new/path
/existing"""
expected_stdout = "/already/here:/new/path:/existing"
env = { "MYPATH" = "/already/here" }

[[test_cases]]
stdin = "/only"
expected_stdout = "/only"
env = { "MYPATH" = "" }