api_gateway.tf

resource "aws_api_gateway_rest_api" "my_api" {
  name        = "MyAPI"
  description = "My API"
}

resource "aws_api_gateway_resource" "api_resource" {
  rest_api_id = aws_api_gateway_rest_api.my_api.id
  parent_id   = aws_api_gateway_rest_api.my_api.root_resource_id
  path_part   = "hello"
}

resource "aws_api_gateway_method" "api_method" {
  rest_api_id   = aws_api_gateway_rest_api.my_api.id
  resource_id   = aws_api_gateway_resource.api_resource.id
  http_method   = "GET"
  authorization = "NONE"
}

resource "aws_api_gateway_integration" "lambda_integration" {
  rest_api_id = aws_api_gateway_rest_api.my_api.id
  resource_id = aws_api_gateway_resource.api_resource.id
  http_method = aws_api_gateway_method.api_method.http_method

  integration_http_method = "POST"
  type                    = "AWS_PROXY"
  uri                     = aws_lambda_function.my_lambda.invoke_arn
}

resource "aws_lambda_permission" "api_lambda_permission" {
  statement_id  = "AllowAPIGatewayInvoke"
  action        = "lambda:InvokeFunction"
  function_name = aws_lambda_function.my_lambda.function_name
  principal     = "apigateway.amazonaws.com"

  source_arn = "${aws_api_gateway_rest_api.my_api.execution_arn}/*/GET/hello"
}

resource "aws_api_gateway_deployment" "my_api_deployment" {
  depends_on = [aws_api_gateway_integration.lambda_integration]

  rest_api_id = aws_api_gateway_rest_api.my_api.id
  stage_name  = "dev" # stage name
  lifecycle {
    create_before_destroy = true
  }
}

data "aws_region" "current" {}

output "hello_invoke_url" {
  value = "https://${aws_api_gateway_rest_api.my_api.id}.execute-api.${data.aws_region.current.name}.amazonaws.com/${aws_api_gateway_deployment.my_api_deployment.stage_name}/hello"
}