#!/usr/bin/env bash

set -euo pipefail

###############################################################################
# Hugo Archive Generator
#
# This script scans all posts in `content/posts`, determines which months fall
# outside of the rolling window, and generates archive pages in:
#
#   content/archive/YYYY/_index.md
#   content/archive/YYYY/MM/_index.md
#
# Additionally:
# - Generates a separate articles archive in:
#     content/archive/articles/YYYY/MM
# - Only includes posts with:
#     layout: post
#     AND without "review" tag
#
# Behavior:
# - Extracts `date:` from front matter (supports ISO timestamps)
# - Groups posts by year/month
# - Skips months within the rolling window (recent content stays on homepage)
# - Reads rolling window from config.toml ([params].archive_rolling_window)
# - Allows CLI override
#
# Usage:
#   ./generate-archive.sh [ROLLING_WINDOW]
#
# Priority:
#   1. CLI argument
#   2. config.toml
#   3. default = 20
#
# Compatibility:
# - Works with macOS default bash (3.2) by avoiding associative arrays
###############################################################################

POSTS_DIR="content/posts"
ARCHIVE_DIR="content/archive"
ARTICLES_ARCHIVE_DIR="content/archive/articles"
CONFIG_FILE="config.toml"

# Default fallback
DEFAULT_WINDOW=20

# Read from config.toml if present
CONFIG_WINDOW=""
if [[ -f "$CONFIG_FILE" ]]; then
  CONFIG_WINDOW=$(grep -E 'archive_rolling_window' "$CONFIG_FILE" \
    | sed -E 's/.*=[[:space:]]*([0-9]+).*/\1/' \
    | head -n1 || true)
fi

# Final rolling window resolution
ROLLING_WINDOW="${1:-${CONFIG_WINDOW:-$DEFAULT_WINDOW}}"

echo "Using rolling window: $ROLLING_WINDOW months"

# Current year/month
CURRENT_YEAR=$(date +%Y)
CURRENT_MONTH=$(date +%m)

current_abs=$((10#$CURRENT_YEAR * 12 + 10#$CURRENT_MONTH))

###############################################################################
# Collect all post months (general archive)
###############################################################################

months_list=$(while IFS= read -r file; do
  raw_date=$(grep -E '^date:' "$file" | head -n1 | sed -E 's/^date:[[:space:]]*"?([^"]*)"?/\1/')

  if [[ -z "${raw_date:-}" ]]; then
    continue
  fi

  year=${raw_date:0:4}
  month=${raw_date:5:2}

  if [[ "$year" =~ ^[0-9]{4}$ && "$month" =~ ^[0-9]{2}$ ]]; then
    echo "$year/$month"
  fi
done < <(find "$POSTS_DIR" -type f -name "*.md") | sort -u)

###############################################################################
# Collect article months (filtered)
###############################################################################

article_months_list=$(while IFS= read -r file; do
  # Must have layout: post
  if ! grep -qE '^layout:[[:space:]]*post' "$file"; then
    continue
  fi

  # Must NOT contain "review" tag
  if grep -qE '^tags:.*review' "$file"; then
    continue
  fi

  raw_date=$(grep -E '^date:' "$file" | head -n1 | sed -E 's/^date:[[:space:]]*"?([^"]*)"?/\1/')

  if [[ -z "${raw_date:-}" ]]; then
    continue
  fi

  year=${raw_date:0:4}
  month=${raw_date:5:2}

  if [[ "$year" =~ ^[0-9]{4}$ && "$month" =~ ^[0-9]{2}$ ]]; then
    echo "$year/$month"
  fi
done < <(find "$POSTS_DIR" -type f -name "*.md") | sort -u)

###############################################################################
# Function to process archive generation
###############################################################################

generate_archive() {
  local list="$1"
  local base_dir="$2"
  local is_articles="$3"

  while IFS= read -r key; do
    year="${key%%/*}"
    month="${key##*/}"

    abs=$((10#$year * 12 + 10#$month))
    diff=$((current_abs - abs))

    if (( diff < ROLLING_WINDOW )); then
      continue
    fi

    year_dir="$base_dir/$year"
    month_dir="$year_dir/$month"

    mkdir -p "$month_dir"

    # Year index
    if [[ ! -f "$year_dir/_index.md" ]]; then
      if [[ "$is_articles" == "true" ]]; then
        cat > "$year_dir/_index.md" <<EOF
---
title: "$year"
year: $year
type: "articles-archive"
layout: "articles-archive"
---
EOF
      else
        cat > "$year_dir/_index.md" <<EOF
---
title: "$year"
year: $year
---
EOF
      fi
    fi

    # Month index
    if [[ "$is_articles" == "true" ]]; then
      cat > "$month_dir/_index.md" <<EOF
---
title: "$year-$month"
year: $year
month: $month
type: "articles-archive"
layout: "articles-archive"
---
EOF
    else
      cat > "$month_dir/_index.md" <<EOF
---
title: "$year-$month"
year: $year
month: $month
---
EOF
    fi

  done <<< "$list"
}

###############################################################################
# Generate both archives
###############################################################################

generate_archive "$months_list" "$ARCHIVE_DIR" "false"
generate_archive "$article_months_list" "$ARTICLES_ARCHIVE_DIR" "true"

echo "Archive structure generated."