92 lines
2.5 KiB
Go
92 lines
2.5 KiB
Go
package wfexec
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import (
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"context"
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"github.com/cortezaproject/corteza-server/pkg/expr"
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)
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type (
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// Iterator can be returned from Exec fn as ExecResponse
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//
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// It helps session's exec fn() to properly navigate through graph
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// by calling is/break/iterator/next function
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Iterator interface {
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// Is the given step this iterator step
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Is(Step) bool
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// Initialize iterator
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Start(context.Context, *expr.Vars) error
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// Break fn is called when loop is forcefully broken
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Break() Step
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Iterator() Step
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// Next is called before each iteration and returns
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// 1st step of the iteration branch and variables that are added to the scope
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Next(context.Context, *expr.Vars) (Step, *expr.Vars, error)
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}
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ResultEvaluator interface {
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EvalResults(ctx context.Context, results *expr.Vars) (out *expr.Vars, err error)
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}
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IteratorHandler interface {
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Start(context.Context, *expr.Vars) error
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More(context.Context, *expr.Vars) (bool, error)
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Next(context.Context, *expr.Vars) (*expr.Vars, error)
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}
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// Handles communication between Session's exec() fn and iterator handler
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genericIterator struct {
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iter, next, exit Step
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h IteratorHandler
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}
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)
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// GenericIterator creates a wrapper around IteratorHandler and
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// returns genericIterator that implements Iterator interface
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func GenericIterator(iter, next, exit Step, h IteratorHandler) Iterator {
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return &genericIterator{
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iter: iter,
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next: next,
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exit: exit,
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h: h,
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}
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}
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func (i *genericIterator) Is(s Step) bool { return i.iter == s }
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func (i *genericIterator) Start(ctx context.Context, s *expr.Vars) error { return i.h.Start(ctx, s) }
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func (i *genericIterator) Break() Step { return i.exit }
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func (i *genericIterator) Iterator() Step { return i.iter }
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// Next calls More and Next functions on iterator handler.
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//
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// If iterator step (iter field) implements ResultEvaluator it calls
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// EvalResults on it before returning it. If iterator step does not implement it,
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// results are omitted.
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func (i *genericIterator) Next(ctx context.Context, scope *expr.Vars) (next Step, out *expr.Vars, err error) {
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var (
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more bool
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results *expr.Vars
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)
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if more, err = i.h.More(ctx, scope); err != nil || !more {
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return
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}
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if results, err = i.h.Next(ctx, scope); err != nil {
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return
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}
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if re, is := i.iter.(ResultEvaluator); is {
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if out, err = re.EvalResults(ctx, results); err != nil {
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return
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}
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}
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next = i.next
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return
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}
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