public override async IAsyncEnumerable <Path> ComputeSelect(EvaluationContext ctx)
{
if (ListCandidate != null && Template != null)
{
// Expression select
var select = ListCandidate.ComputeSelect(ctx);
await foreach (var atom in select)
{
yield return(atom);
}
// Expression paths
var paths = ListCandidate.ComputePaths(ctx);
await foreach (var path in paths)
{
yield return(path.Append("Id"));
}
// Inner template select
var scopedCtx = ctx.Clone();
scopedCtx.SetLocalVariable(IteratorVariableName, new EvaluationVariable(
eval: TemplateUtil.VariableThatThrows(IteratorVariableName),
selectResolver: () => select,
pathsResolver: () => paths
));
await foreach (var atom in Template.ComputeSelect(scopedCtx))
{
yield return(atom);
}
}
}
public override async Task GenerateOutputs(EvaluationContext ctx)
{
_listCandidate ??= TemplexBase.Parse(ListExpression);
if (_listCandidate != null)
{
var listObj = (await _listCandidate.Evaluate(ctx)) ?? new List <object>();
if (listObj is IList list)
{
foreach (var listItem in list)
{
// Initialize new evaluation context with the new variable in it
var scopedCtx = ctx.Clone();
scopedCtx.SetLocalVariable(IteratorVariableName, new EvaluationVariable(
evalAsync: () => Task.FromResult(listItem),
selectResolver: () => AsyncUtil.Empty <Path>(), // It doesn't matter when generating output
pathsResolver: () => AsyncUtil.Empty <Path>() // It doesn't matter when generating output
));
// Run the template again on that context
await Inner.GenerateOutputs(scopedCtx);
}
}
else
{
throw new TemplateException($"Expression does not evaluate to a list ({_listCandidate}).");
}
}
}
public override async Task GenerateOutputs(EvaluationContext ctx)
{
if (ctx.TryGetApiResult(QueryInfo, out object result))
{
ctx = ctx.Clone();
ctx.SetLocalVariable(VariableName, new EvaluationVariable(value: result));
}
await Inner.GenerateOutputs(ctx);
}
/// <summary>
/// Clones the <see cref="EvaluationContext"/> and returns a new one that contains the new variable.
/// </summary>
private EvaluationContext GetScopeLocalContext(EvaluationContext ctx)
{
var variable = new EvaluationVariable(
evalAsync: () => Value.Evaluate(ctx),
selectResolver: () => Value.ComputeSelect(ctx),
pathsResolver: () => Value.ComputePaths(ctx));
var ctxClone = ctx.Clone();
ctxClone.SetLocalVariable(VariableName, variable);
return(ctxClone);
}
public override async IAsyncEnumerable <Path> ComputeSelect(EvaluationContext ctx)
{
var ctxClone = ctx.Clone();
ctxClone.SetLocalVariable(VariableName, new EvaluationVariable(
eval: TemplateUtil.VariableThatThrows(varName: VariableName), // This is what makes it a "static" context
pathsResolver: () => AsyncUtil.Singleton(Path.Empty(QueryInfo))
));
await foreach (var path in Inner.ComputeSelect(ctxClone))
{
yield return(path);
}
}
/// <summary>
/// Clones the <see cref="EvaluationContext"/> and returns a new one that contains the new variable.
/// </summary>
private EvaluationContext GetScopeLocalContext(EvaluationContext ctx)
{
_varExpression ??= TemplexBase.Parse(VariableExpression);
var variable = new EvaluationVariable(
evalAsync: () => _varExpression.Evaluate(ctx),
selectResolver: () => _varExpression.ComputeSelect(ctx),
pathsResolver: () => _varExpression.ComputePaths(ctx));
var ctxClone = ctx.Clone();
ctxClone.SetLocalVariable(VariableName, variable);
return(ctxClone);
}
public override async Task GenerateOutput(StringBuilder builder, EvaluationContext ctx, Func <string, string> encodeFunc = null)
{
if (ListCandidate != null && Template != null)
{
var listObj = (await ListCandidate.Evaluate(ctx)) ?? new List <object>();
if (listObj is IList list)
{
int index = 0;
foreach (var listItem in list)
{
// Initialize new evaluation context with the new variable in it
var scopedCtx = ctx.Clone();
scopedCtx.SetLocalVariable(IteratorVariableName, new EvaluationVariable(
evalAsync: () => Task.FromResult(listItem),
selectResolver: () => AsyncUtil.Empty <Path>(), // It doesn't matter when generating output
pathsResolver: () => AsyncUtil.Empty <Path>() // It doesn't matter when generating output
));
// Index, useful for setting line numbers
scopedCtx.SetLocalVariable(IteratorVariableName + "_index", new EvaluationVariable(
evalAsync: () => Task.FromResult <object>(index),
selectResolver: () => AsyncUtil.Empty <Path>(), // It doesn't matter when generating output
pathsResolver: () => AsyncUtil.Empty <Path>() // It doesn't matter when generating output
));
// Run the template again on that context
await Template.GenerateOutput(builder, scopedCtx, encodeFunc);
index++;
}
}
else
{
throw new TemplateException($"Foreach expression could not be applied. Expression ({ListCandidate}) does not evaluate to a list.");
}
}
}
