#!/usr/bin/env bash
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
REPO_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
INVENTORY_FILE="${REPO_ROOT}/homelab.yml"
README_TEMPLATE="${REPO_ROOT}/README.md.tmpl"
README_OUTPUT="${REPO_ROOT}/README.md"

usage() {
    cat <<'USAGE'
Usage: scripts/render-docs [--check]

Render generated Markdown docs from repo-local templates.

Options:
  --check   fail if generated docs differ from committed output
USAGE
}

read_inventory_value() {
    local path="$1"

    python3 - "${INVENTORY_FILE}" "${path}" <<'PY'
import re
import sys

inventory_file, requested_path = sys.argv[1:3]
stack = []
values = {}
pattern = re.compile(r"^(\s*)([A-Za-z_][A-Za-z0-9_]*):(?:\s*(.*?))?\s*$")

with open(inventory_file, encoding="utf-8") as handle:
    for raw_line in handle:
        if not raw_line.strip() or raw_line.lstrip().startswith("#") or raw_line.lstrip().startswith("- "):
            continue
        match = pattern.match(raw_line.rstrip("\n"))
        if not match:
            continue
        indent = len(match.group(1))
        key = match.group(2)
        value = (match.group(3) or "").strip()
        while stack and stack[-1][0] >= indent:
            stack.pop()
        current_path = ".".join([item[1] for item in stack] + [key])
        if value == "":
            stack.append((indent, key))
            continue
        if " #" in value:
            value = value.split(" #", 1)[0].strip()
        values[current_path] = value.strip("\"'")

value = values.get(requested_path)
if not value:
    raise SystemExit(1)
print(value)
PY
}

render_readme() {
    local main_script="$1"

    if grep -Eo '{{[[:space:]]*[A-Za-z_][A-Za-z0-9_]*[[:space:]]*}}' "${README_TEMPLATE}" |
        grep -Evq '{{[[:space:]]*main_script[[:space:]]*}}'; then
        printf 'Unsupported template variable in %s\n' "${README_TEMPLATE}" >&2
        return 1
    fi

    sed "s/{{[[:space:]]*main_script[[:space:]]*}}/${main_script}/g" "${README_TEMPLATE}"
}

main() {
    local mode="render"
    local main_script
    local rendered

    case "${1:-}" in
        "")
            ;;
        --check)
            mode="check"
            ;;
        -h | --help)
            usage
            return 0
            ;;
        *)
            usage >&2
            return 2
            ;;
    esac

    if [[ ! -s "${INVENTORY_FILE}" ]]; then
        printf 'Missing homelab inventory: %s\n' "${INVENTORY_FILE}" >&2
        return 1
    fi
    if [[ ! -s "${README_TEMPLATE}" ]]; then
        printf 'Missing README template: %s\n' "${README_TEMPLATE}" >&2
        return 1
    fi

    main_script="$(read_inventory_value metadata.main_script)"
    if [[ -z "${main_script}" ]]; then
        printf 'homelab.yml metadata.main_script must not be empty\n' >&2
        return 1
    fi

    rendered="$(mktemp)"
    render_readme "${main_script}" >"${rendered}"

    if [[ "${mode}" == "check" ]]; then
        "${REPO_ROOT}/scripts/render-service-catalog" --check
        if ! cmp -s "${rendered}" "${README_OUTPUT}"; then
            printf 'Generated README.md is stale. Run scripts/render-docs.\n' >&2
            diff -u "${README_OUTPUT}" "${rendered}" || true
            rm -f "${rendered}"
            return 1
        fi
        printf 'docs are current\n'
        rm -f "${rendered}"
        return 0
    fi

    mv "${rendered}" "${README_OUTPUT}"
    "${REPO_ROOT}/scripts/render-service-catalog"
    printf 'Rendered %s from %s\n' "${README_OUTPUT}" "${README_TEMPLATE}"
}

main "$@"