A minimalist single-page to-do editor with a built-in Gantt chart.

• Browser: plain HTML/CSS/JavaScript (no React, no build step)
• Server: Python (single file) for static hosting + persistence
• Storage: one JSON file on disk (single document)

1. Start the server:

python server.py

2. Open:

http://127.0.0.1:8000

The server writes state to data/doc.json.

Layout:

• Left pane (~33%): hierarchical outline to-do list
• Right pane (~67%): Gantt chart; one row per visible task

Outline:

• Enter: add a task below
• Tab / Shift+Tab: indent / outdent
• Arrow Up/Down: move selection
• Double-click (or F2 / e): edit task text
• Space (or x): toggle done (strike-through)
• Alt+Left / Alt+Right: collapse / expand subtree
• Backspace: delete selected task (deletes subtree)

Autosave:

• Any change triggers a debounced save to the server
• Reload restores the same state from disk

Dates are parsed from the task text and stored as explicit start/end dates in ISO YYYY-MM-DD format.

Supported patterns:

1. One date: YYYY-MM-DD (start=end)
2. Range from today: today - YYYY-MM-DD (start=today)
3. Two dates: YYYY-MM-DD - YYYY-MM-DD or YYYY-MM-DD to YYYY-MM-DD
4. Duration: YYYY-MM-DD 3d (end = start + 3 days)

Definitions:

• Explicit dates: start / end on a task (from parsing/editing)
• Effective dates: what the UI/Gantt renders after roll-up

Rules:

• Leaf task:
  • If only a start date exists, it is treated as a milestone (end=start).
• Parent task:
  • Child window is computed from children’s effective dates (min start, max end).
  • Explicit bounds win per-bound:
    • No explicit start/end: effective = child window
    • Explicit start only: effectiveStart = start, effectiveEnd = childMaxEnd (or start if none)
    • Explicit end only: effectiveStart = childMinStart (or end if none), effectiveEnd = end
    • Explicit start+end: effective = explicit

Warnings (red):

• Invalid effective range (start > end)
• Parent explicit range doesn’t cover the child window (inconsistent)

• Derived from the outline (done/collapsed state and visible rows)
• Autoscaled timeline range based on visible tasks’ effective dates
• Grid markings:
  • Minor: days
  • Major: weeks (week starts on Sunday)

• Server endpoints:
  • GET /api/doc -> { revision, updatedAt, doc }
  • PUT /api/doc with { baseRevision, doc }
• If baseRevision is stale, server returns 409 conflict

• server.py — Python server (static + API)
• static/index.html — UI shell
• static/styles.css — minimal brutal styling
• static/app.js — state, editor, date parsing, gantt rendering
• data/doc.json — persisted single document