cn0 split stats.source.sh into aggregate/render/filter-album modules

Pure code move: split the ~1248-line stats.source.sh (SRP+SoC) into three
cohesive modules, all functions and STATS_* constants/globals moved verbatim:

- stats-aggregate.source.sh: EXIF parsing, bucketing, _stats_tally,
  reset/collect_photo_exif_stats and the STATS_* maps.
- stats-render.source.sh: stats overview page (sections, bars, leaderboard,
  render_stats_page, _stats_build_body, _stats_filter_link, background pickers).
- stats-filter-album.source.sh: per-filter mini-albums (render_filter_pages,
  gallery/view/thumbnail builders, _stats_enqueue_filter_album).

Updated LIB_SOURCES accordingly. No logic change (verified: all 55 functions and
top-level globals preserved; full suite, shellcheck, check-generated, diff all
pass). The SoC point (HTML built in bash rather than templates) is left for a
follow-up (nn0/qn0).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 0 insertions, 1248 deletions

diff --git a/src/lib/stats.source.sh b/src/lib/stats.source.sh
deleted file mode 100644
index cda2b61..0000000
--- a/src/lib/stats.source.sh
+++ /dev/null
@@ -1,1248 +0,0 @@
-# Stats aggregation for the album stats page (feature plan:
-# /home/paul/.pi/plans/shuriken-stats-site.md, field audit:
-# docs/stats-exif-audit.md). This module turns the per-photo
-# `identify -verbose` output that album.source.sh already caches into
-# aggregated, photographer-friendly counters.
-#
-# Scope: aggregation only. Rendering (stats.tmpl / camera.tmpl) lives in the
-# sibling tasks pm0/rm0/um0; this module just fills the data structures they
-# read.
-#
-# ----------------------------------------------------------------------------
-# Public API / handoff contract
-# ----------------------------------------------------------------------------
-# collect_photo_exif_stats iterates the album's photos and fills these globals
-# (all declared with `declare -gA` so the render tasks can read them after the
-# call without namerefs):
-#
-#   STATS_CAMERAS[<camera label>]      = count          (camera leaderboard)
-#   STATS_LENSES[<lens model>]         = count           (sparse; may be empty)
-#   STATS_YEARS[<YYYY>]                = count
-#   STATS_MONTHS[<01..12>]             = count
-#   STATS_APERTURE[<bucket>]           = count           (e.g. "f/2.8")
-#   STATS_SHUTTER[<bucket>]            = count           (e.g. "1/250s")
-#   STATS_ISO[<bucket>]                = count           (e.g. "400")
-#   STATS_FOCAL[<bucket>]              = count           (e.g. "35-70mm")
-#   STATS_MEGAPIXELS[<bucket>]         = count           (e.g. "10-20MP")
-#   STATS_ASPECT[<bucket>]             = count           (e.g. "3:2")
-#   STATS_ORIENTATION[<bucket>]        = count           (Landscape/Portrait/Square)
-#   STATS_FORMAT[<bucket>]             = count           (JPEG/PNG/WEBP/GIF)
-#   STATS_EXPOSURE_PROGRAM[<label>]    = count           (decoded enum)
-#   STATS_METERING[<label>]            = count           (decoded enum)
-#   STATS_WHITE_BALANCE[<label>]       = count           (Auto/Manual)
-#   STATS_FLASH[<label>]               = count           (Fired/Did not fire; sparse)
-#   STATS_TOTALS[photos]               = number of photos seen
-#
-# It also fills the filter mini-album maps (see reset_photo_exif_stats):
-# STATS_FILTER_PHOTOS / STATS_FILTER_TITLE keyed by a unique "pagebase", and
-# STATS_FILTER_PAGEBASE mapping "<prefix>\x1f<label>" -> pagebase so the stats
-# rows can link to each bucket's mini-album.
-#
-# The render side should treat every per-category array as possibly empty
-# (sparse data) and only render a section when it has entries. STATS_TOTALS
-# gives the denominator for percentages.
-
-# Reset every stats global to an empty associative array. Called at the start of
-# collect_photo_exif_stats so repeated invocations (e.g. tests, --refresh) do
-# not accumulate stale counts.
-reset_photo_exif_stats() {
-    declare -gA STATS_CAMERAS=()
-    declare -gA STATS_LENSES=()
-    declare -gA STATS_YEARS=()
-    declare -gA STATS_MONTHS=()
-    declare -gA STATS_APERTURE=()
-    declare -gA STATS_SHUTTER=()
-    declare -gA STATS_ISO=()
-    declare -gA STATS_FOCAL=()
-    declare -gA STATS_MEGAPIXELS=()
-    declare -gA STATS_ASPECT=()
-    declare -gA STATS_ORIENTATION=()
-    declare -gA STATS_FORMAT=()
-    declare -gA STATS_EXPOSURE_PROGRAM=()
-    declare -gA STATS_METERING=()
-    declare -gA STATS_WHITE_BALANCE=()
-    declare -gA STATS_FLASH=()
-    declare -gA STATS_TOTALS=()
-    STATS_TOTALS[photos]=0
-    # Every tallied bucket (across all categories) becomes a clickable filter
-    # mini-album. These map a unique, filename-safe "pagebase" (e.g. iso-400,
-    # camera-canon-eos-r5, year-2023) to that bucket's data:
-    #   STATS_FILTER_PHOTOS[pagebase]   = newline-separated photo list
-    #   STATS_FILTER_TITLE[pagebase]    = human heading for the gallery page
-    #   STATS_FILTER_OWNER[pagebase]    = catkey owning the pagebase (collisions)
-    #   STATS_FILTER_PAGEBASE[catkey]   = pagebase for a "<prefix>\x1f<label>"
-    # so the bar rows can link to the matching mini-album.
-    declare -gA STATS_FILTER_PHOTOS=()
-    declare -gA STATS_FILTER_TITLE=()
-    declare -gA STATS_FILTER_OWNER=()
-    declare -gA STATS_FILTER_PAGEBASE=()
-    # Cached background photo list (filled lazily by _stats_random_background);
-    # cleared so a fresh generation rescans the (possibly changed) photos dir.
-    declare -ga STATS_BG_PHOTOS=()
-    STATS_BG_PHOTOS_LOADED=''
-}
-
-# Decode an EXIF rational ("num/den") to a decimal with `scale` digits.
-# Guards den == 0 and tolerates plain decimals (some tools write "0.5"). Prints
-# nothing for unparseable input so callers can skip it. The audit lists this as
-# shared work for FNumber/FocalLength/ExposureTime.
-_stats_rational_to_decimal() {
-    local -r value="$1"; shift
-    local -r scale="${1:-2}"
-
-    if [[ "$value" =~ ^([0-9]+)/([0-9]+)$ ]]; then
-        local -r num="${BASH_REMATCH[1]}"
-        local -r den="${BASH_REMATCH[2]}"
-        if (( den == 0 )); then
-            return
-        fi
-        awk -v n="$num" -v d="$den" -v s="$scale" \
-            'BEGIN { printf "%.*f", s, n / d }'
-        return
-    fi
-    # Already a bare decimal/integer: echo it back so buckets can use it.
-    if [[ "$value" =~ ^[0-9]+([.][0-9]+)?$ ]]; then
-        printf '%s' "$value"
-    fi
-}
-
-# Bucket an f-number (decimal) to the nearest standard aperture stop, matching
-# the boundaries in the plan (≤f/1.8 ... ≥f/22). The decimal is compared with
-# awk so we avoid bash integer-only math on fractional stops.
-_stats_aperture_bucket() {
-    local -r fnum="$1"; shift
-
-    awk -v f="$fnum" 'BEGIN {
-        if (f <= 1.8) { print "f/1.8 or wider"; }
-        else if (f <= 2.2) { print "f/2"; }
-        else if (f <= 3.2) { print "f/2.8"; }
-        else if (f <= 4.5) { print "f/4"; }
-        else if (f <= 6.7) { print "f/5.6"; }
-        else if (f <= 9.5) { print "f/8"; }
-        else if (f <= 13) { print "f/11"; }
-        else if (f <= 19) { print "f/16"; }
-        else { print "f/22 or narrower"; }
-    }'
-}
-
-# Bucket a shutter speed (already normalized to seconds) into the plan's ranges.
-# Faster shutters are smaller numbers, so the ladder runs from short to long.
-_stats_shutter_bucket() {
-    local -r seconds="$1"; shift
-
-    awk -v s="$seconds" 'BEGIN {
-        if (s <= 1/4000) { print "1/4000s or faster"; }
-        else if (s <= 1/2000) { print "1/2000s"; }
-        else if (s <= 1/1000) { print "1/1000s"; }
-        else if (s <= 1/500) { print "1/500s"; }
-        else if (s <= 1/250) { print "1/250s"; }
-        else if (s <= 1/125) { print "1/125s"; }
-        else if (s <= 1/60) { print "1/60s"; }
-        else if (s <= 1/30) { print "1/30s"; }
-        else if (s <= 1/15) { print "1/15s"; }
-        else if (s <= 1/8) { print "1/8s"; }
-        else if (s <= 1/4) { print "1/4s"; }
-        else if (s <= 1/2) { print "1/2s"; }
-        else if (s <= 1) { print "1s"; }
-        else { print "longer than 1s"; }
-    }'
-}
-
-# Bucket an integer ISO to the next standard value at or above it. Plain integer
-# per the audit; uses bash arithmetic since ISO is always an integer.
-_stats_iso_bucket() {
-    local -ri iso="$1"
-
-    if (( iso <= 50 )); then printf '50'
-    elif (( iso <= 100 )); then printf '100'
-    elif (( iso <= 200 )); then printf '200'
-    elif (( iso <= 400 )); then printf '400'
-    elif (( iso <= 800 )); then printf '800'
-    elif (( iso <= 1600 )); then printf '1600'
-    elif (( iso <= 3200 )); then printf '3200'
-    elif (( iso <= 6400 )); then printf '6400'
-    elif (( iso <= 12800 )); then printf '12800'
-    elif (( iso <= 25600 )); then printf '25600'
-    else printf 'over 25600'
-    fi
-}
-
-# Bucket a focal length (decimal mm) by the plan's lens ranges. Labelled as
-# physical focal length, not 35mm-equivalent, per the audit.
-_stats_focal_bucket() {
-    local -r mm="$1"; shift
-
-    awk -v m="$mm" 'BEGIN {
-        if (m < 24) { print "under 24mm"; }
-        else if (m < 35) { print "24-35mm"; }
-        else if (m < 70) { print "35-70mm"; }
-        else if (m < 135) { print "70-135mm"; }
-        else if (m <= 200) { print "135-200mm"; }
-        else { print "over 200mm"; }
-    }'
-}
-
-# Bucket megapixels (W*H/1e6) by the plan's ranges.
-_stats_megapixels_bucket() {
-    local -r mp="$1"; shift
-
-    awk -v p="$mp" 'BEGIN {
-        if (p < 2) { print "under 2MP"; }
-        else if (p < 5) { print "2-5MP"; }
-        else if (p < 10) { print "5-10MP"; }
-        else if (p < 20) { print "10-20MP"; }
-        else if (p < 40) { print "20-40MP"; }
-        else if (p <= 80) { print "40-80MP"; }
-        else { print "over 80MP"; }
-    }'
-}
-
-# Reduce W:H by GCD and match common photographic aspect ratios. The audit
-# recommends deriving this from Geometry rather than EXIF.
-_stats_aspect_bucket() {
-    local -ri width="$1"; shift
-    local -ri height="$1"; shift
-    local -i a="$width"
-    local -i b="$height"
-    local -i t
-
-    if (( width <= 0 || height <= 0 )); then
-        return
-    fi
-    while (( b != 0 )); do
-        t=$b
-        b=$(( a % b ))
-        a=$t
-    done
-    case "$(( width / a )):$(( height / a ))" in
-        3:2|2:3) printf '3:2' ;;
-        4:3|3:4) printf '4:3' ;;
-        16:9|9:16) printf '16:9' ;;
-        1:1) printf '1:1' ;;
-        5:4|4:5) printf '5:4' ;;
-        *) printf 'other' ;;
-    esac
-}
-
-# Orientation from width vs height. The audit prefers this over the native
-# Orientation rotation flag, which is frequently absent or already baked in.
-_stats_orientation_bucket() {
-    local -ri width="$1"; shift
-    local -ri height="$1"; shift
-
-    if (( width > height )); then printf 'Landscape'
-    elif (( height > width )); then printf 'Portrait'
-    else printf 'Square'
-    fi
-}
-
-# Decode the ExposureProgram enum (0-8) to a friendly label. ImageMagick emits
-# the bare integer; the audit supplies this map.
-_stats_exposure_program_label() {
-    case "$1" in
-        1) printf 'Manual' ;;
-        2) printf 'Program AE' ;;
-        3) printf 'Aperture priority' ;;
-        4) printf 'Shutter priority' ;;
-        5) printf 'Creative' ;;
-        6) printf 'Action' ;;
-        7) printf 'Portrait' ;;
-        8) printf 'Landscape' ;;
-        *) printf 'Not defined' ;;
-    esac
-}
-
-# Decode the MeteringMode enum to a friendly label per the audit's map.
-_stats_metering_label() {
-    case "$1" in
-        1) printf 'Average' ;;
-        2) printf 'Center-weighted' ;;
-        3) printf 'Spot' ;;
-        4) printf 'Multi-spot' ;;
-        5) printf 'Multi-segment' ;;
-        6) printf 'Partial' ;;
-        255) printf 'Other' ;;
-        *) printf 'Unknown' ;;
-    esac
-}
-
-# Standard EXIF WhiteBalance is only a 2-value enum (0 Auto, 1 Manual); the
-# richer presets live in MakerNotes and are not exposed by identify (audit).
-_stats_white_balance_label() {
-    case "$1" in
-        0) printf 'Auto' ;;
-        1) printf 'Manual' ;;
-        *) return ;;
-    esac
-}
-
-# Decode the EXIF Flash bitmask: bit 0 indicates the flash fired. The audit
-# warns this tag is frequently missing, so callers must tolerate absence.
-_stats_flash_label() {
-    local -ri flash="$1"
-
-    if (( flash & 1 )); then printf 'Flash fired'
-    else printf 'No flash'
-    fi
-}
-
-# Build a filename-safe slug for camera-<slug>.html. Lowercase, non-alphanumeric
-# runs collapsed to a single dash, leading/trailing dashes trimmed.
-_stats_slug() {
-    local slug="${1,,}"
-
-    slug="${slug//[^a-z0-9]/-}"
-    while [[ "$slug" == *--* ]]; do
-        slug="${slug//--/-}"
-    done
-    slug="${slug#-}"
-    slug="${slug%-}"
-    printf '%s' "$slug"
-}
-
-# Join Make + Model into a single camera label, reusing the same dedup logic as
-# album.source.sh's tooltip builder (handles "Model already includes Make").
-_stats_camera_label() {
-    local -r make="$1"; shift
-    local -r model="$1"; shift
-
-    if [ -z "$model" ]; then
-        printf '%s' "$make"
-        return
-    fi
-    if [ -z "$make" ]; then
-        printf '%s' "$model"
-        return
-    fi
-    case "$model" in
-        "$make"|"$make "*) printf '%s' "$model" ;;
-        *) printf '%s %s' "$make" "$model" ;;
-    esac
-}
-
-# Tally a photo's camera (Make+Model) and, when present, its lens into their
-# leaderboard counts and filter mini-albums. Skips photos with no Make/Model.
-_stats_record_camera() {
-    local -n values_ref="$1"; shift
-    local -r photo="$1"; shift
-    local label
-
-    label=$(_stats_camera_label "${values_ref[Make]:-}" "${values_ref[Model]:-}")
-    _stats_tally STATS_CAMERAS camera "$label" "$label" "$photo"
-    if [ -n "${values_ref[LensModel]:-}" ]; then
-        _stats_tally STATS_LENSES lens \
-            "${values_ref[LensModel]}" "Lens ${values_ref[LensModel]}" "$photo"
-    fi
-}
-
-# Record year and month counters from DateTimeOriginal ("YYYY:MM:DD HH:MM:SS").
-# Parsed by substring per the audit: the colons in the date part are not
-# standard, so this must not be fed to `date -d`. Falls back to the digitized /
-# plain DateTime tags.
-_stats_record_datetime() {
-    local -n values_ref="$1"; shift
-    local -r photo="$1"; shift
-    local raw=''
-    local key
-    local -ra month_names=( '' January February March April May June July
-        August September October November December )
-
-    for key in DateTimeOriginal DateTimeDigitized DateTime; do
-        if [ -n "${values_ref[$key]:-}" ]; then
-            raw="${values_ref[$key]}"
-            break
-        fi
-    done
-    if [[ ! "$raw" =~ ^([0-9]{4}):([0-9]{2}): ]]; then
-        return
-    fi
-    local -r year="${BASH_REMATCH[1]}"
-    local -r month="${BASH_REMATCH[2]}"
-    _stats_tally STATS_YEARS year "$year" "Year $year" "$photo"
-    _stats_tally STATS_MONTHS month "$month" \
-        "${month_names[10#$month]:-Month $month}" "$photo"
-}
-
-# Record the aperture, shutter, ISO and focal-length histograms. Each uses the
-# fallback tag order the audit recommends and the rational decoder for the
-# fiddly fields. Missing/unparseable values are simply skipped.
-_stats_record_exposure() {
-    local -n values_ref="$1"; shift
-    local -r photo="$1"; shift
-    local decimal raw bucket
-
-    raw="${values_ref[FNumber]:-}"
-    decimal=$(_stats_rational_to_decimal "$raw")
-    if [ -n "$decimal" ]; then
-        bucket=$(_stats_aperture_bucket "$decimal")
-        _stats_tally STATS_APERTURE aperture "$bucket" "Aperture $bucket" "$photo"
-    fi
-
-    raw="${values_ref[ExposureTime]:-}"
-    decimal=$(_stats_rational_to_decimal "$raw" 6)
-    if [ -n "$decimal" ]; then
-        bucket=$(_stats_shutter_bucket "$decimal")
-        _stats_tally STATS_SHUTTER shutter "$bucket" "Shutter $bucket" "$photo"
-    fi
-
-    # ISO fallback order mirrors album.source.sh's tooltip builder
-    # (ISOSpeedRatings -> PhotographicSensitivity -> ISO) so a photo carrying
-    # several ISO tags buckets the same value it shows in its tooltip.
-    raw="${values_ref[ISOSpeedRatings]:-${values_ref[PhotographicSensitivity]:-${values_ref[ISO]:-}}}"
-    if [[ "$raw" =~ ^[0-9]+$ ]]; then
-        bucket=$(_stats_iso_bucket "$raw")
-        _stats_tally STATS_ISO iso "$bucket" "ISO $bucket" "$photo"
-    fi
-
-    raw="${values_ref[FocalLength]:-}"
-    decimal=$(_stats_rational_to_decimal "$raw")
-    if [ -n "$decimal" ]; then
-        bucket=$(_stats_focal_bucket "$decimal")
-        _stats_tally STATS_FOCAL focal "$bucket" "Focal length $bucket" "$photo"
-    fi
-}
-
-# Record the decoded enum stats (exposure program, metering, white balance,
-# flash). Each is skipped when the tag is absent or decodes to nothing (empty
-# labels are dropped by _stats_tally).
-_stats_record_enums() {
-    local -n values_ref="$1"; shift
-    local -r photo="$1"; shift
-    local label
-
-    if [ -n "${values_ref[ExposureProgram]:-}" ]; then
-        label=$(_stats_exposure_program_label "${values_ref[ExposureProgram]}")
-        _stats_tally STATS_EXPOSURE_PROGRAM exposure-program \
-            "$label" "Exposure program $label" "$photo"
-    fi
-    if [ -n "${values_ref[MeteringMode]:-}" ]; then
-        label=$(_stats_metering_label "${values_ref[MeteringMode]}")
-        _stats_tally STATS_METERING metering "$label" "Metering $label" "$photo"
-    fi
-    if [ -n "${values_ref[WhiteBalance]:-}" ]; then
-        label=$(_stats_white_balance_label "${values_ref[WhiteBalance]}")
-        _stats_tally STATS_WHITE_BALANCE white-balance \
-            "$label" "White balance $label" "$photo"
-    fi
-    if [[ "${values_ref[Flash]:-}" =~ ^[0-9]+$ ]]; then
-        label=$(_stats_flash_label "${values_ref[Flash]}")
-        _stats_tally STATS_FLASH flash "$label" "Flash $label" "$photo"
-    fi
-}
-
-# Record dimension stats (megapixels, aspect ratio, orientation) from the native
-# Geometry field. Geometry is "WxH+x+y"; the leading WxH is what we need. These
-# are native fields, not exif: lines, so they come from the separate native
-# parser path in _stats_parse_identify_stream.
-_stats_record_dimensions() {
-    local -n values_ref="$1"; shift
-    local -r photo="$1"; shift
-    local mp bucket
-
-    if [[ ! "${values_ref[__geometry]:-}" =~ ^([0-9]+)x([0-9]+) ]]; then
-        return
-    fi
-    local -ri width="${BASH_REMATCH[1]}"
-    local -ri height="${BASH_REMATCH[2]}"
-
-    mp=$(awk -v w="$width" -v h="$height" 'BEGIN { printf "%.4f", w * h / 1000000 }')
-    bucket=$(_stats_megapixels_bucket "$mp")
-    _stats_tally STATS_MEGAPIXELS megapixels "$bucket" "Megapixels $bucket" "$photo"
-    bucket=$(_stats_aspect_bucket "$width" "$height")
-    _stats_tally STATS_ASPECT aspect "$bucket" "Aspect ratio $bucket" "$photo"
-    bucket=$(_stats_orientation_bucket "$width" "$height")
-    _stats_tally STATS_ORIENTATION orientation "$bucket" "$bucket" "$photo"
-}
-
-# Record the file-format breakdown. The audit's cheapest path keys off the file
-# extension (no identify parsing), so this maps the extension to a format label.
-# This trusts the extension over actual content: a misnamed file (e.g. a PNG
-# named .jpg) is counted by its name. Unrecognized extensions fall into 'other'.
-_stats_record_format() {
-    local -r photo="$1"; shift
-    local extension="${photo##*.}"
-    local label
-
-    if [[ "$photo" != *.* ]]; then
-        return
-    fi
-    case "${extension,,}" in
-        jpg|jpeg) label=JPEG ;;
-        png) label=PNG ;;
-        webp) label=WEBP ;;
-        gif) label=GIF ;;
-        *) label=other ;;
-    esac
-    _stats_tally STATS_FORMAT format "$label" "$label" "$photo"
-}
-
-# Increment a counter in the named global associative array. Centralizes the
-# "create-or-add-one" idiom and skips empty keys so unparseable buckets do not
-# create blank entries.
-_stats_bump() {
-    local -n array_ref="$1"; shift
-    local -r key="$1"; shift
-
-    if [ -z "$key" ]; then
-        return
-    fi
-    array_ref["$key"]=$(( ${array_ref["$key"]:-0} + 1 ))
-}
-
-# Field separator used inside STATS_FILTER_PAGEBASE keys ("<prefix>\x1f<label>").
-# A control char that cannot appear in a prefix or an EXIF label.
-declare -gr STATS_FILTER_KEYSEP=$'\x1f'
-
-# Resolve the unique, filename-safe pagebase for a (prefix, label) filter into
-# the named output variable, caching it so repeated tallies reuse it. Distinct
-# labels in the same category whose slug collides (e.g. two camera models
-# differing only in punctuation) get a numeric suffix. Uses a nameref output --
-# not command substitution -- so the STATS_FILTER_OWNER/PAGEBASE mutations
-# persist in the caller's shell.
-_stats_resolve_filter_pagebase() {
-    local -n pagebase_out_ref="$1"; shift
-    local -r prefix="$1"; shift
-    local -r label="$1"; shift
-    local -r catkey="$prefix$STATS_FILTER_KEYSEP$label"
-    local base slug
-    local -i suffix=2
-
-    if [ -n "${STATS_FILTER_PAGEBASE[$catkey]:-}" ]; then
-        pagebase_out_ref="${STATS_FILTER_PAGEBASE[$catkey]}"
-        return
-    fi
-    slug=$(_stats_slug "$label")
-    if [ -z "$slug" ]; then
-        slug=other
-    fi
-    base="$prefix-$slug"
-    pagebase_out_ref="$base"
-    while [ -n "${STATS_FILTER_OWNER[$pagebase_out_ref]:-}" ] \
-        && [ "${STATS_FILTER_OWNER[$pagebase_out_ref]}" != "$catkey" ]; do
-        pagebase_out_ref="$base-$suffix"
-        (( ++suffix ))
-    done
-    STATS_FILTER_OWNER["$pagebase_out_ref"]="$catkey"
-    STATS_FILTER_PAGEBASE["$catkey"]="$pagebase_out_ref"
-}
-
-# Tally one photo into a bucket: bump the category count AND record the photo on
-# the bucket's filter mini-album (keyed by a unique pagebase). prefix namespaces
-# the pagebase per category, label is the bucket key (also the count-array key),
-# and title is the gallery heading shown for that bucket. Skips empty labels.
-_stats_tally() {
-    local -r count_array="$1"; shift
-    local -r prefix="$1"; shift
-    local -r label="$1"; shift
-    local -r title="$1"; shift
-    local -r photo="$1"; shift
-    local pagebase
-
-    if [ -z "$label" ]; then
-        return
-    fi
-    _stats_bump "$count_array" "$label"
-    _stats_resolve_filter_pagebase pagebase "$prefix" "$label"
-    if [ -n "${STATS_FILTER_PHOTOS[$pagebase]:-}" ]; then
-        STATS_FILTER_PHOTOS["$pagebase"]+=$'\n'"$photo"
-    else
-        STATS_FILTER_PHOTOS["$pagebase"]="$photo"
-        STATS_FILTER_TITLE["$pagebase"]="$title"
-    fi
-}
-
-# Parse one photo's `identify -verbose` stream into an associative array. The
-# current album.source.sh regex only captures exif: lines, but the audit needs
-# the native Geometry field for dimensions, so this adds a second match path
-# storing it under the synthetic key __geometry.
-_stats_parse_identify_stream() {
-    local -n values_ref="$1"; shift
-    local line
-
-    values_ref=()
-    while IFS= read -r line; do
-        if [[ "$line" =~ ^[[:space:]]*exif:([^:]+):[[:space:]]*(.*)$ ]]; then
-            values_ref["${BASH_REMATCH[1]}"]="${BASH_REMATCH[2]}"
-        elif [[ "$line" =~ ^[[:space:]]*Geometry:[[:space:]]*(.*)$ ]]; then
-            values_ref[__geometry]="${BASH_REMATCH[1]}"
-        fi
-    done
-}
-
-# Aggregate a single photo: parse its identify stream (from stdin) and update
-# every counter. Split out from collect_photo_exif_stats so tests can feed a
-# synthetic fixture without stubbing the cache layer.
-accumulate_photo_stats() {
-    local -r photo="$1"; shift
-    # exif_values is filled and read through the nameref helpers below.
-    # shellcheck disable=SC2034
-    local -A exif_values=()
-
-    _stats_parse_identify_stream exif_values
-    STATS_TOTALS[photos]=$(( STATS_TOTALS[photos] + 1 ))
-    _stats_record_camera exif_values "$photo"
-    _stats_record_datetime exif_values "$photo"
-    _stats_record_exposure exif_values "$photo"
-    _stats_record_enums exif_values "$photo"
-    _stats_record_dimensions exif_values "$photo"
-    _stats_record_format "$photo"
-}
-
-# Iterate the album's incoming photos, read each one's cached identify output via
-# album.source.sh's cache helper, and aggregate it into the STATS_* globals.
-# This is the entry point the render tasks call before reading the counters.
-collect_photo_exif_stats() {
-    local photo
-
-    reset_photo_exif_stats
-    while IFS= read -r photo; do
-        accumulate_photo_stats "$photo" \
-            < <(cached_photo_identify_output "$photo" "$INCOMING_DIR/$photo")
-    done < <(incoming_image_files)
-}
-
-# ----------------------------------------------------------------------------
-# Rendering (task pm0)
-# ----------------------------------------------------------------------------
-# render_stats_page turns the STATS_* globals filled by the aggregation above
-# into a static stats.html. The page is variable-length (each category may be
-# empty, sparse, or large) which does not fit the fixed field-spec template
-# engine cleanly, so we follow the same approach view/details pages use for
-# their dynamic EXIF table: build the whole body as an HTML string here, hand it
-# to stats.tmpl through the raw context field stats_body, and let the engine wrap
-# it with the shared header/footer chrome. Bars are plain CSS (width as a percent
-# of the section's top bucket) so the output stays JavaScript-free.
-
-# Print the largest counter in the named stats array, or 0 when it is empty.
-# Used to scale each section's bars relative to its own busiest bucket.
-_stats_max_count() {
-    local -n counts_ref="$1"; shift
-    local key
-    local -i max=0
-
-    for key in "${!counts_ref[@]}"; do
-        if (( counts_ref[$key] > max )); then
-            max=${counts_ref[$key]}
-        fi
-    done
-    printf '%d' "$max"
-}
-
-# Print the integer percentage count/total (0 when total is 0). awk keeps the
-# rounding off bash integer math; STATS_TOTALS[photos] is the denominator.
-_stats_percent() {
-    local -ri count="$1"; shift
-    local -ri total="$1"; shift
-
-    if (( total <= 0 )); then
-        printf '0'
-        return
-    fi
-    awk -v c="$count" -v t="$total" 'BEGIN { printf "%.0f", 100 * c / t }'
-}
-
-# Emit one bar-chart <li>: an already-escaped label, a CSS-width bar scaled to
-# the section maximum, and the count plus its share of all photos. Callers escape
-# labels themselves because some come from EXIF (camera/lens) and some are
-# trusted bucket names we build internally.
-_stats_bar_row() {
-    local -r label_html="$1"; shift
-    local -ri count="$1"; shift
-    local -ri total="$1"; shift
-    local -ri max="$1"; shift
-    local -i width=0
-
-    if (( max > 0 )); then
-        width=$(( 100 * count / max ))
-    fi
-    printf '    <li>'
-    printf '<span class="stats-label">%s</span>' "$label_html"
-    printf '<span class="stats-bar-track">'
-    printf '<span class="stats-bar-fill" style="width:%d%%"></span></span>' \
-        "$width"
-    printf '<span class="stats-count">%d (%s%%)</span>' \
-        "$count" "$(_stats_percent "$count" "$total")"
-    printf '</li>\n'
-}
-
-# Open a <section> with an escaped heading and the <ul> bar container. Split from
-# the row emitters so every section shares identical chrome. An optional second
-# argument adds an extra CSS class to the <ul> (e.g. the leaderboard uses it to
-# space out and separate its rows of long, wrapping camera names).
-_stats_section_open() {
-    local -r heading="$1"; shift
-    local -r list_class="${1:-}"
-    local heading_html
-    local ul_class='stats-bars'
-
-    if [ -n "$list_class" ]; then
-        ul_class+=" $list_class"
-    fi
-    heading_html=$(_html_escape "$heading")
-    printf '<section class="stats-section">\n'
-    printf '<h2>%s</h2>\n' "$heading_html"
-    printf '<ul class="%s">\n' "$ul_class"
-}
-
-_stats_section_close() {
-    printf '</ul>\n</section>\n'
-}
-
-# Wrap an escaped label in a link to its filter mini-album. Every tallied bucket
-# has a pagebase recorded in STATS_FILTER_PAGEBASE during aggregation, keyed by
-# "<prefix>\x1f<label>"; if one is (unexpectedly) absent, the plain label is
-# returned so the row still renders. The stats page and the filter pages share
-# the dist root, so the href is just "<pagebase>.html".
-_stats_filter_link() {
-    local -r prefix="$1"; shift
-    local -r label="$1"; shift
-    local -r label_html="$1"; shift
-    local -r catkey="$prefix$STATS_FILTER_KEYSEP$label"
-    local pagebase
-
-    pagebase="${STATS_FILTER_PAGEBASE[$catkey]:-}"
-    if [ -n "$pagebase" ]; then
-        # The stats overview lives at stats/index.html and each mini-album at
-        # stats/<pagebase>/index.html, so link relative to the overview.
-        printf '<a href="%s/index.html">%s</a>' "$pagebase" "$label_html"
-    else
-        printf '%s' "$label_html"
-    fi
-}
-
-# Render the camera leaderboard: one bar per camera, sorted by count descending,
-# each label linking to its camera mini-album. Camera labels come from EXIF, so
-# the text is HTML-escaped. Skipped entirely when no camera data was collected.
-_stats_render_camera_section() {
-    local -ri total="$1"; shift
-    local label
-    local row_html
-    local -i max
-
-    if (( ${#STATS_CAMERAS[@]} == 0 )); then
-        return
-    fi
-    max=$(_stats_max_count STATS_CAMERAS)
-    _stats_section_open 'Camera leaderboard' 'stats-leaderboard'
-    while IFS= read -r label; do
-        row_html=$(_stats_filter_link camera "$label" "$(_html_escape "$label")")
-        _stats_bar_row "$row_html" "${STATS_CAMERAS[$label]}" "$total" "$max"
-    done < <(_stats_keys_by_count_desc STATS_CAMERAS)
-    _stats_section_close
-}
-
-# Print an array's keys ordered by descending count (ties broken by key) so the
-# busiest bucket leads. Used for the leaderboard and other count-ranked sections.
-# LC_ALL=C pins the tie-break collation so the generated page is byte-identical
-# across locales/machines (reproducible static output).
-_stats_keys_by_count_desc() {
-    local -n counts_ref="$1"; shift
-    local key
-
-    for key in "${!counts_ref[@]}"; do
-        printf '%d\t%s\n' "${counts_ref[$key]}" "$key"
-    done | LC_ALL=C sort -t $'\t' -k1,1nr -k2,2 | cut -f2-
-}
-
-# Render a histogram section using an explicit bucket order (e.g. apertures from
-# wide to narrow) rather than count ranking, so the axis reads naturally. Only
-# buckets that actually occurred are emitted, and the whole section is skipped
-# when none did. Bucket labels are internal/trusted but still escaped for safety.
-_stats_render_ordered_section() {
-    local -r heading="$1"; shift
-    local -r array_name="$1"; shift
-    local -r prefix="$1"; shift
-    local -ri total="$1"; shift
-    local -n counts_ref="$array_name"
-    local bucket
-    local row_html
-    local -i max
-
-    if (( ${#counts_ref[@]} == 0 )); then
-        return
-    fi
-    max=$(_stats_max_count "$array_name")
-    _stats_section_open "$heading"
-    for bucket in "$@"; do
-        if [ -z "${counts_ref[$bucket]:-}" ]; then
-            continue
-        fi
-        row_html=$(_stats_filter_link "$prefix" "$bucket" "$(_html_escape "$bucket")")
-        _stats_bar_row "$row_html" "${counts_ref[$bucket]}" "$total" "$max"
-    done
-    _stats_section_close
-}
-
-# Render a section ranked by count (cameras aside). Used where there is no
-# natural axis order: years, lenses, and the decoded enum categories.
-_stats_render_ranked_section() {
-    local -r heading="$1"; shift
-    local -r array_name="$1"; shift
-    local -r prefix="$1"; shift
-    local -ri total="$1"; shift
-    local -n counts_ref="$array_name"
-    local key
-    local row_html
-    local -i max
-
-    if (( ${#counts_ref[@]} == 0 )); then
-        return
-    fi
-    max=$(_stats_max_count "$array_name")
-    _stats_section_open "$heading"
-    while IFS= read -r key; do
-        row_html=$(_stats_filter_link "$prefix" "$key" "$(_html_escape "$key")")
-        _stats_bar_row "$row_html" "${counts_ref[$key]}" "$total" "$max"
-    done < <(_stats_keys_by_count_desc "$array_name")
-    _stats_section_close
-}
-
-# Render the temporal sections. Years rank by count; months walk Jan..Dec in
-# calendar order using human month names for the labels.
-_stats_render_temporal_sections() {
-    local -ri total="$1"; shift
-
-    _stats_render_ranked_section 'Photos per year' STATS_YEARS year "$total"
-    _stats_render_month_section "$total"
-}
-
-# Render the per-month histogram in calendar order. The aggregator keys months
-# by zero-padded number (01..12); this maps each to its English name so the axis
-# is readable, and reuses the ordered-section omit-when-empty behaviour inline.
-_stats_render_month_section() {
-    local -ri total="$1"; shift
-    local -ra month_names=(
-        '' January February March April May June July August
-        September October November December )
-    local -i month
-    local key
-    local -i max
-
-    if (( ${#STATS_MONTHS[@]} == 0 )); then
-        return
-    fi
-    max=$(_stats_max_count STATS_MONTHS)
-    _stats_section_open 'Photos per month'
-    for (( month = 1; month <= 12; month++ )); do
-        key=$(printf '%02d' "$month")
-        if [ -z "${STATS_MONTHS[$key]:-}" ]; then
-            continue
-        fi
-        _stats_bar_row \
-            "$(_stats_filter_link month "$key" "${month_names[$month]}")" \
-            "${STATS_MONTHS[$key]}" "$total" "$max"
-    done
-    _stats_section_close
-}
-
-# Render the exposure histograms in photographer-friendly axis order (the same
-# bucket ladders the aggregator's *_bucket helpers produce).
-_stats_render_exposure_sections() {
-    local -ri total="$1"; shift
-
-    _stats_render_ordered_section 'Aperture' STATS_APERTURE aperture "$total" \
-        'f/1.8 or wider' 'f/2' 'f/2.8' 'f/4' 'f/5.6' 'f/8' 'f/11' 'f/16' \
-        'f/22 or narrower'
-    _stats_render_ordered_section 'Shutter speed' STATS_SHUTTER shutter "$total" \
-        '1/4000s or faster' '1/2000s' '1/1000s' '1/500s' '1/250s' '1/125s' \
-        '1/60s' '1/30s' '1/15s' '1/8s' '1/4s' '1/2s' '1s' 'longer than 1s'
-    _stats_render_ordered_section 'ISO' STATS_ISO iso "$total" \
-        '50' '100' '200' '400' '800' '1600' '3200' '6400' '12800' '25600' \
-        'over 25600'
-    _stats_render_ordered_section 'Focal length' STATS_FOCAL focal "$total" \
-        'under 24mm' '24-35mm' '35-70mm' '70-135mm' '135-200mm' 'over 200mm'
-}
-
-# Render the dimension histograms (megapixels, aspect ratio, orientation) and
-# the file-format breakdown, each in its natural axis order.
-_stats_render_dimension_sections() {
-    local -ri total="$1"; shift
-
-    _stats_render_ordered_section 'Megapixels' STATS_MEGAPIXELS megapixels \
-        "$total" \
-        'under 2MP' '2-5MP' '5-10MP' '10-20MP' '20-40MP' '40-80MP' 'over 80MP'
-    _stats_render_ordered_section 'Aspect ratio' STATS_ASPECT aspect "$total" \
-        '3:2' '4:3' '16:9' '1:1' '5:4' 'other'
-    _stats_render_ordered_section 'Orientation' STATS_ORIENTATION orientation \
-        "$total" 'Landscape' 'Portrait' 'Square'
-    _stats_render_ordered_section 'File format' STATS_FORMAT format "$total" \
-        'JPEG' 'PNG' 'WEBP' 'GIF' 'other'
-}
-
-# Render the decoded enum sections and the (sparse) lens leaderboard. All rank by
-# count and self-skip when empty, so absent tags simply omit their section.
-_stats_render_enum_sections() {
-    local -ri total="$1"; shift
-
-    _stats_render_ranked_section 'Lenses' STATS_LENSES lens "$total"
-    _stats_render_ranked_section 'Exposure program' \
-        STATS_EXPOSURE_PROGRAM exposure-program "$total"
-    _stats_render_ranked_section 'Metering mode' STATS_METERING metering "$total"
-    _stats_render_ranked_section 'White balance' STATS_WHITE_BALANCE \
-        white-balance "$total"
-    _stats_render_ranked_section 'Flash' STATS_FLASH flash "$total"
-}
-
-# Assemble the full stats body from every section in display order. Returns the
-# HTML on stdout; render_stats_page captures it into the stats_body context var.
-_stats_build_body() {
-    local -ri total="${STATS_TOTALS[photos]:-0}"
-
-    printf '<p class="stats-total">%d photos analysed.</p>\n' "$total"
-    _stats_render_camera_section "$total"
-    _stats_render_temporal_sections "$total"
-    _stats_render_exposure_sections "$total"
-    _stats_render_dimension_sections "$total"
-    _stats_render_enum_sections "$total"
-}
-
-# Public render entry point (handoff for task rm0). Builds the body from the
-# already-populated STATS_* globals and renders stats.html via the template
-# engine, wrapping the body with the shared header/footer the way view/details
-# pages do. Call collect_photo_exif_stats first to fill the globals.
-#   render_stats_page <html_dir> <backhref> [page_name]
-# html_dir is the dist-relative output directory (top-level album: "."),
-# backhref is the relative path back to the album root ("." for a top-level
-# stats.html), and page_name defaults to "stats" -> stats.html.
-# Pick a seeded-random photo for a stats/camera page's blurred background, the
-# same way the album preview pages do. The context seeds the choice so each page
-# gets a stable (per RANDOM_SEED) but varied background. Degrades to an empty
-# string (plain black background) when no photos exist, e.g. unit tests that
-# render the page without a populated photos directory.
-# Load the sorted photo list for blurred backgrounds once into a global. This
-# runs for every filter page (thousands of them), so the per-call directory scan
-# randomphoto would otherwise do dominates the build. render_filter_pages loads
-# it before forking the render jobs so each background subshell inherits the
-# populated array instead of rescanning.
-_stats_load_background_photos() {
-    if [ -n "${STATS_BG_PHOTOS_LOADED:-}" ]; then
-        return
-    fi
-    declare -ga STATS_BG_PHOTOS=()