use serde::{Deserialize, Serialize};
use uuid::Uuid;

/// AI 队列任务协议。
///
/// 定义在协议 crate 中，使生产方（git / pulls）与消费方（agent / aihost）
/// 都能引用同一份载荷定义而不产生 crate 依赖环。
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
#[serde(tag = "kind", rename_all = "snake_case")]
pub enum AgentTask {
    PullReview {
        job_id: Uuid,
        repo_id: Uuid,
        pull_request_id: Uuid,
        head_sha: String,
        /// 输出语言（BCP-47 或 `auto`）；`None` 时用 `[ai].output_language`。
        #[serde(default)]
        language: Option<String>,
    },
    CommitReview {
        job_id: Uuid,
        repo_id: Uuid,
        commit_sha: String,
        #[serde(default)]
        language: Option<String>,
    },
    RepoSummary {
        job_id: Uuid,
        repo_id: Uuid,
        head_sha: String,
        base_sha: Option<String>,
        limit: Option<u64>,
        #[serde(default)]
        language: Option<String>,
    },
    ReleaseNotes {
        job_id: Uuid,
        repo_id: Uuid,
        release_id: Uuid,
        tag_name: String,
        from_sha: Option<String>,
        to_sha: String,
        #[serde(default)]
        language: Option<String>,
    },
}

impl AgentTask {
    #[must_use]
    pub fn job_id(&self) -> Uuid {
        match self {
            Self::PullReview { job_id, .. }
            | Self::CommitReview { job_id, .. }
            | Self::RepoSummary { job_id, .. }
            | Self::ReleaseNotes { job_id, .. } => *job_id,
        }
    }

    #[must_use]
    pub fn repo_id(&self) -> Uuid {
        match self {
            Self::PullReview { repo_id, .. }
            | Self::CommitReview { repo_id, .. }
            | Self::RepoSummary { repo_id, .. }
            | Self::ReleaseNotes { repo_id, .. } => *repo_id,
        }
    }

    /// 稳定字符串标识，与 `ai_job.kind` 的取值一致。
    #[must_use]
    pub fn kind_str(&self) -> &'static str {
        match self {
            Self::PullReview { .. } => "pull_review",
            Self::CommitReview { .. } => "commit_review",
            Self::RepoSummary { .. } => "repo_summary",
            Self::ReleaseNotes { .. } => "release_notes",
        }
    }

    #[must_use]
    pub fn target_id(&self) -> Option<Uuid> {
        match self {
            Self::PullReview {
                pull_request_id, ..
            } => Some(*pull_request_id),
            Self::ReleaseNotes { release_id, .. } => Some(*release_id),
            Self::CommitReview { .. } | Self::RepoSummary { .. } => None,
        }
    }

    /// 该任务请求的输出语言（未指定时为 `None`，由消费侧取配置缺省）。
    #[must_use]
    pub fn language(&self) -> Option<&str> {
        match self {
            Self::PullReview { language, .. }
            | Self::CommitReview { language, .. }
            | Self::RepoSummary { language, .. }
            | Self::ReleaseNotes { language, .. } => language.as_deref(),
        }
    }

    #[must_use]
    pub fn target_ref(&self) -> Option<String> {
        match self {
            Self::PullReview { head_sha, .. } => Some(head_sha.clone()),
            Self::CommitReview { commit_sha, .. } => Some(commit_sha.clone()),
            Self::RepoSummary { head_sha, .. } => Some(head_sha.clone()),
            Self::ReleaseNotes { tag_name, .. } => Some(tag_name.clone()),
        }
    }

    pub fn encode(&self) -> Result<Vec<u8>, serde_json::Error> {
        serde_json::to_vec(self)
    }

    pub fn decode(payload: &[u8]) -> Result<Self, serde_json::Error> {
        serde_json::from_slice(payload)
    }
}