Allow charts to be based on remote CSV files

[methnen]

This has been requested multiple times now.

https://wordpress.org/support/topic/dynamic-cvs-uploads-2

[zbtirrell]

Implementation Plan: Remote CSV Data Source

Approach

Add per-chart opt-in remote CSV support: a URL field, refresh interval selector, and "Sync Now" button in the existing CSV section of the spreadsheet meta box. A new lazy-loaded class (M_Chart_Remote_CSV) handles fetching, parsing, cron scheduling, and cleanup — following the same patterns as the existing sub-classes (M_Chart_Admin, M_Chart_Parse, etc.).

When a remote URL is set, the spreadsheet becomes read-only (visual overlay) to signal that edits will be overwritten on next sync. Clearing the URL restores manual editing.

Files to Modify

1. components/class-m-chart.php — Add meta fields + accessor

New meta fields added to $chart_meta_fields:

'remote_csv_url'       => '',
'remote_csv_interval'  => 'none',   // 'none', 'hourly', 'twicedaily', 'daily'
'remote_csv_last_sync' => 0,

Validation in validate_post_meta():

• remote_csv_url: validated with esc_url_raw() (same pattern as source_url)
• remote_csv_interval: whitelisted against valid values
• remote_csv_last_sync: absint()

Plus a lazy-loader accessor remote_csv() following the parse() pattern.

2. components/class-m-chart-remote-csv.php — New file

Core class with:

• fetch_remote_csv( $url ) — Uses wp_safe_remote_get() (SSRF-safe) with 15s timeout and 5MB size limit. Parses response with the parseCSV library + fix_csv_data_array() — identical pipeline to ajax_import_csv().
• sync_chart( $post_id ) — Fetches remote CSV, validates data through m_chart()->validate_data(), writes to post meta, sets transient to prevent re-fetching within the interval.
• ajax_sync_remote_csv() — AJAX handler for "Sync Now" button. Same security pattern as ajax_import_csv(): post type check, nonce verification, capability check. Returns parsed 2D array via wp_send_json_success().
• cron_sync( $post_id ) — WP Cron callback.
• maybe_schedule_cron() — Hooks m_chart_update_post_meta. Manages cron scheduling based on URL + interval.
• maybe_refresh_data() — Hooks m_chart_get_chart_start. Checks transient; if expired, refreshes data before render.
• cleanup_on_delete() — Hooks before_delete_post. Unschedules cron, deletes transient.

3. components/class-m-chart-admin.php — Pass remote_csv_url to JS via wp_localize_script

4. components/templates/spreadsheet-meta-box.php — Admin UI added inside the existing #m-chart-csv div:

• URL text input
• Auto-refresh <select> (Manual only, Hourly, Twice Daily, Daily)
• "Sync Now" button
• "Last synced X ago" status line
• Error/progress message elements

5. components/js/m-chart-admin.js — New handle_remote_csv() method:

• "Sync Now" AJAX handler that loads response data into the spreadsheet
• toggle_remote_csv_mode() that adds a read-only overlay when a URL is set

6. components/sass/_spreadsheet.scss — Styles for the remote CSV section and read-only overlay

Error Handling

• Bad URL / timeout / non-200 → WP_Error surfaced in admin UI
• Empty or unparseable CSV → descriptive error message
• Cron failures are silent — existing data preserved, next run retries
• Clearing the URL → cron unscheduled, spreadsheet becomes editable