[Bug Report] Panic in Generate

[kermieisinthehouse]

Probably introduced in #2167

panic: runtime error: integer divide by zero

goroutine 105 [running]:
github.com/stashapp/stash/pkg/manager.(*GeneratorInfo).configure(0xc000136500)
    github.com/stashapp/stash/pkg/manager/generator.go:115 +0x9d
github.com/stashapp/stash/pkg/manager.(*PreviewGenerator).Generate(0xc000018310)
    github.com/stashapp/stash/pkg/manager/generator_preview.go:56 +0x78
github.com/stashapp/stash/pkg/manager.(*GeneratePreviewTask).Start(0xc00039a000, {0x198fc98, 0xc0001fa600})
    github.com/stashapp/stash/pkg/manager/task_generate_preview.go:59 +0x4b5
github.com/stashapp/stash/pkg/manager.(*GenerateJob).Execute.func3()
    github.com/stashapp/stash/pkg/manager/task_generate.go:127 +0x3c
github.com/stashapp/stash/pkg/job.(*Progress).ExecuteTask(0xc0001fa700, {0xc00038e160, 0xa9}, 0xc0001f2d00)
    github.com/stashapp/stash/pkg/job/progress.go:153 +0xcd
created by github.com/stashapp/stash/pkg/manager.(*GenerateJob).Execute
    github.com/stashapp/stash/pkg/manager/task_generate.go:126 +0x3bb

Stash Version: (from Settings -> About):
0.12.0

Desktop (please complete the following information):

• OS: Docker on MacOS

[kermieisinthehouse]

It looks like setting segments or duration to 0 in the preview generation options will cause division by 0. We need some validation there.

[bnkai]

#2167 only changed code for the sprites generation so i dont think it was related

I think the issue is the Number of segments in preview that is set to 0
From a quick look

stash/pkg/manager/generator.go

Line 115 in 0388aec

g.NthFrame = g.NumberOfFrames / g.ChunkCount

stash/pkg/manager/generator.go

Line 149 in 0388aec

stepSize = duration / float64(g.ChunkCount)

could be the cause

For the segment duration option we already take care of that as having too small of a duration had some issues

stash/pkg/manager/generator_preview.go

Line 111 in 0388aec

if durationSegment < 0.75 { // a very short duration can create files without a video stream

For the chunkcount idk if its better to set it to 1 if its <1 (doesnt make sense with numbers <1) in the above function, before stepSize, offset := g.Info.getStepSizeAndOffset() or just/also alter the generator functions

stash/pkg/manager/generator.go

Line 115 in 0388aec

g.NthFrame = g.NumberOfFrames / g.ChunkCount

stash/pkg/manager/generator.go

Line 149 in 0388aec

stepSize = duration / float64(g.ChunkCount)

to also check

An extra chek here chould also be added

stash/pkg/manager/task_generate_preview.go

Line 53 in 0388aec

generator.Info.ChunkCount = *t.Options.PreviewSegments

[kermieisinthehouse]

This is what it was, the user had set segments to 0. We should disallow that in the UI.