What is the allusion of Li Shangyin's poem "The cuckoo cries in spring" in Jinse?

A hint to the royal cuckoo. According to legend, the monarch of Shu in the late Zhou Dynasty was Du Yu. Later, he retired from Zen, unfortunately died, his soul turned into a bird, crowed in late spring, and even bled in his mouth. The voice is sad and touching, named Du Fu. Spring generally refers to the yearning for love, but also can be compared to the pursuit of good things. The "spring heart" here is linked with Du Fu's mourning, which actually contains the meaning of hurting and hating spring. In Li Shangyin's poems, hurting spring refers to worrying about the country and the people, hurting time and sentimental life experience. The so-called "eternal change of heart, though broken, is not as good as hurting spring" (Qujiang), "Creative farewell to hurting spring" (Du Sixun) and "Nothing happened in my life, but I hurt myself in spring" (Qinghe) can all be used as evidence. "Wang Chunxin's cuckoo crow" shows a picture shrouded in sadness: it symbolizes that cuckoo has turned into a ghost. In the wailing of blood and tears, there is an endless grievance. This picture, on the one hand, shows the sadness and sadness of the voice, on the other hand, it also means that a person's desire for love and hate (good wishes and feelings of worrying about the country and the people and sentimental life experience when injured) is all entrusted to the sad and broken voice of cuckoo crying blood. The word "entrust" in the sentence, that is, the meaning of "entrust", is the crowning touch of the whole sentence, which not only writes that Du Yuzhi entrusted the spring to Du Fu, but also writes that the poet entrusted the spring to hate. It implies the nature of those who place their "desire for love", which is really wonderful.