It's a long story.

Meaning

The explanation is complex and lengthy.

Examples

• John: 'Why are you so late?'
• Alice: '<b>It's a long story.</b> Let's just say there was a major traffic jam.'
• John: '<b>It's a long story,</b> involving a YouTube tutorial and a lot of patience.'
• Alice: 'How did you manage to fix that broken appliance?'