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CORE-1120: refactor the code to obtain the before_id and after_id…
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… fields in the response body for the /v2/messages endpoint
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@slr71
slr71 committed Oct 3, 2020
1 parent 5907e4a commit 31c5ae9
Showing 1 changed file with 35 additions and 131 deletions.
166 changes: 35 additions & 131 deletions db/listings.go
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Original file line number Diff line number Diff line change
Expand Up @@ -450,25 +450,35 @@ func v2GetNotificationCount(tx *sql.Tx, params *V2NotificationListingParameters)
return total, nil
}

// runBoundaryIDQueryParams defines the parameters to runBoundaryIDQuery.
// runBoundaryIDQueryParams defines the parameters to runBoundaryIDQuery. The intent of this structure is to provide
// a way to pass named parameters to runBoundaryIDQuery.
type runBoundaryIDQueryParams struct {
Tx *sql.Tx
QueryBuilder sq.SelectBuilder
WhereFn func(sq.SelectBuilder, string, *time.Time) (sq.SelectBuilder, error)
ListingParams *V2NotificationListingParameters
ComparisonID string
ComparisonTimestamp *time.Time
SortOrder query.SortOrder
Offset uint64
}

// runBoundaryIDQuery runs a single boundary ID query and returns the result.
func runBoundaryIDQuery(params runBoundaryIDQueryParams) (string, error) {
builder := params.QueryBuilder
func runBoundaryIDQuery(params *runBoundaryIDQueryParams) (string, error) {
var err error

// Add the where clause to the query if necessary.
if params.WhereFn != nil {
builder, err = params.WhereFn(params.QueryBuilder, params.ComparisonID, params.ComparisonTimestamp)
// Build the base query.
builder := v2ListNotificationsBaseQuery(params.ListingParams).Column("n.id")

// A WHERE clause is needed if we're querying relative to an existing message.
if params.ComparisonID != "" && params.ComparisonTimestamp != nil {

// The specific WHERE clause to add depends on the sort order.
whereFn := v2AddBeforeIDWhereClause
if params.SortOrder == query.SortOrderAscending {
whereFn = v2AddAfterIDWhereClause
}

// Add the clause to the query.
builder, err = whereFn(builder, params.ComparisonID, params.ComparisonTimestamp)
if err != nil {
return "", err
}
Expand Down Expand Up @@ -503,132 +513,26 @@ func runBoundaryIDQuery(params runBoundaryIDQueryParams) (string, error) {
return id, nil
}

// boundaryIDFinder defines an interface for obtaining the IDs of messages just beyond the boundaries of the current
// page. There are several cases that we need to account for, and there will be one implementation of this interface
// for each case.
type boundaryIDFinder interface {
GetBoundaryIDs() (string, string, error)
}

// v2GetBoundaryIDs obtains the IDs of the messages just beyond the boundaries of the current page.
func v2GetBoundaryIDs(tx *sql.Tx, params *V2NotificationListingParameters) (string, string, error) {
var beforeID, afterID string
var err error

// Begin building the query.
queryBuilder := v2ListNotificationsBaseQuery(params).Column("n.id")

// Handle the case where the before ID was specified.
if params.BeforeID != "" {
if params.Limit > 0 {
beforeID, err = runBoundaryIDQuery(
runBoundaryIDQueryParams{
Tx: tx,
QueryBuilder: queryBuilder,
WhereFn: v2AddBeforeIDWhereClause,
ComparisonID: params.BeforeID,
ComparisonTimestamp: params.BeforeTimestamp,
SortOrder: query.SortOrderDescending,
Offset: params.Limit,
},
)
if err != nil {
return "", "", err
}
}

afterID, err = runBoundaryIDQuery(
runBoundaryIDQueryParams{
Tx: tx,
QueryBuilder: queryBuilder,
WhereFn: v2AddAfterIDWhereClause,
ComparisonID: params.BeforeID,
ComparisonTimestamp: params.BeforeTimestamp,
SortOrder: query.SortOrderAscending,
Offset: 1,
},
)
if err != nil {
return "", "", err
}

return beforeID, afterID, nil
}

// Handle the case where the after ID was specified.
if params.AfterID != "" {
if params.Limit > 0 {
afterID, err = runBoundaryIDQuery(
runBoundaryIDQueryParams{
Tx: tx,
QueryBuilder: queryBuilder,
WhereFn: v2AddAfterIDWhereClause,
ComparisonID: params.AfterID,
ComparisonTimestamp: params.AfterTimestamp,
SortOrder: query.SortOrderAscending,
Offset: params.Limit,
},
)
if err != nil {
return "", "", err
}
}

beforeID, err = runBoundaryIDQuery(
runBoundaryIDQueryParams{
Tx: tx,
QueryBuilder: queryBuilder,
WhereFn: v2AddBeforeIDWhereClause,
ComparisonID: params.AfterID,
ComparisonTimestamp: params.AfterTimestamp,
SortOrder: query.SortOrderDescending,
Offset: 1,
},
)
if err != nil {
return "", "", err
}

return beforeID, afterID, nil
}

// Handle the case where no boundary ID was specified and the sort order is ascending.
if params.SortOrder == query.SortOrderAscending {
beforeID = ""

if params.Limit > 0 {
afterID, err = runBoundaryIDQuery(
runBoundaryIDQueryParams{
Tx: tx,
QueryBuilder: queryBuilder,
SortOrder: query.SortOrderAscending,
Offset: params.Limit,
},
)
if err != nil {
return "", "", err
}
} else {
afterID = ""
}

return beforeID, afterID, nil
}

// Handle the case where no boundary ID was specified and the sort order is descending.
if params.SortOrder == query.SortOrderDescending {
afterID = ""

if params.Limit > 0 {
beforeID, err = runBoundaryIDQuery(
runBoundaryIDQueryParams{
Tx: tx,
QueryBuilder: queryBuilder,
SortOrder: query.SortOrderDescending,
Offset: params.Limit,
},
)
if err != nil {
return "", "", err
}
} else {
beforeID = ""
}

return beforeID, afterID, nil
// Handle each case that we have to accommodate.
switch {
case params.BeforeID != "":
return newBeforeIDBoundaryFinder(tx, params).GetBoundaryIDs()
case params.AfterID != "":
return newAfterIDBoundaryFinder(tx, params).GetBoundaryIDs()
case params.SortOrder == query.SortOrderAscending:
return newAscendingBoundaryFinder(tx, params).GetBoundaryIDs()
case params.SortOrder == query.SortOrderDescending:
return newDescendingBoundaryFinder(tx, params).GetBoundaryIDs()
}

// If execution get to this point, we have problems.
Expand Down

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