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package cli
// ================================================================
// Decide whether to insert a flatten or unflatten verb at the end of the
// chain. See also repl/verbs.go which handles the same issue in the REPL.
//
// ----------------------------------------------------------------
// PROBLEM TO BE SOLVED:
//
// JSON has nested structures and CSV et al. do not. For example:
// {
// "req" : {
// "method": "GET",
// "path": "api/check",
// }
// }
//
// For CSV we flatten this down to
//
// {
// "req.method": "GET",
// "req.path": "api/check"
// }
//
// ----------------------------------------------------------------
// APPROACH:
//
// Use the Principle of Least Surprise (POLS).
//
// * If input is JSON and output is JSON:
// o Records can be nested from record-read
// o They remain that way through the Miller record-processing stream
// o They are nested on record-write
// o No action needs to be taken
//
// * If input is JSON and output is non-JSON:
// o Records can be nested from record-read
// o They remain that way through the Miller record-processing stream
// o On record-write, nested structures will be converted to string (carriage
// returns and all) using json_stringify. People *might* want this but
// (using POLS) we will (by default) AUTO-FLATTEN for them. There is a
// --no-auto-unflatten CLI flag for those who want it.
//
// * If input is non-JSON and output is non-JSON:
// o If there is a "req.method" field, people should be able to do
// 'mlr sort -f req.method' with no surprises. (Again, POLS.) Therefore
// no auto-unflatten on input. People can insert an unflatten verb
// into their verb chain if they really want unflatten for non-JSON
// files.
// o The DSL can make nested data, so AUTO-FLATTEN at output.
//
// * If input is non-JSON and output is JSON:
// o Default is to auto-unflatten at output.
// o There is a --no-auto-unflatten for those who want it.
//
// * Overriding these: if the last verb the user has explicitly provided is
// flatten, don't undo that by putting an unflatten right after.
//
// ================================================================
func DecideFinalFlatten(writerOptions *TWriterOptions) bool {
ofmt := writerOptions.OutputFileFormat
if writerOptions.AutoFlatten {
if ofmt != "json" {
return true
}
}
return false
}
func DecideFinalUnflatten(
options *TOptions,
verbSequences [][]string,
) bool {
numVerbs := len(verbSequences)
if numVerbs > 0 {
lastVerbSequence := verbSequences[numVerbs-1]
if len(lastVerbSequence) > 0 {
lastVerbName := lastVerbSequence[0]
if lastVerbName == "flatten" {
return false
}
}
}
ifmt := options.ReaderOptions.InputFileFormat
ofmt := options.WriterOptions.OutputFileFormat
if options.WriterOptions.AutoUnflatten {
if ifmt != "json" {
if ofmt == "json" {
return true
}
}
}
return false
}
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