use serde::{Deserialize, Serialize};

const CHANGELOG_R2_PREFIX: &str = "changelog/releases-";

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct ChangelogItem {
    pub title: String,
    #[serde(default)]
    pub desc: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ChangelogSection {
    #[serde(default)]
    pub r#type: String,
    #[serde(default)]
    pub title: String,
    #[serde(default)]
    pub items: Vec<ChangelogItem>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ChangelogRelease {
    pub tag: String,
    #[serde(default)]
    pub name: String,
    #[serde(default)]
    pub date: String,
    #[serde(default)]
    pub sections: Vec<ChangelogSection>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct ChangelogData {
    #[serde(default)]
    pub updated_at: String,
    #[serde(default)]
    pub releases: Vec<ChangelogRelease>,
}

/// Normalize UI locale / short lang into `cn` or `en` (matches R2 file naming).
pub fn normalize_changelog_lang(lang: &str) -> &'static str {
    let trimmed = lang.trim();
    if trimmed.eq_ignore_ascii_case("cn")
        || trimmed.eq_ignore_ascii_case("zh")
        || trimmed.eq_ignore_ascii_case("zh-CN")
        || trimmed.eq_ignore_ascii_case("zh-TW")
    {
        "cn"
    } else {
        "en"
    }
}

pub async fn fetch_changelog(lang: &str) -> Result<ChangelogData, String> {
    let lang = normalize_changelog_lang(lang);
    let client = build_changelog_http_client()?;
    let url = format!("{}{CHANGELOG_R2_PREFIX}{lang}.json", crate::R2_CDN_BASE);

    let resp = client
        .get(&url)
        .header(reqwest::header::USER_AGENT, "dbx-changelog")
        .send()
        .await
        .and_then(|r| r.error_for_status())
        .map_err(|e| format!("Failed to fetch changelog: {e}"))?;

    let mut data: ChangelogData = resp.json().await.map_err(|e| format!("Failed to parse changelog: {e}"))?;
    data.releases.retain(|release| !release.tag.trim().is_empty());
    Ok(data)
}

fn build_changelog_http_client() -> Result<reqwest::Client, String> {
    let mut builder =
        reqwest::Client::builder().timeout(std::time::Duration::from_secs(15)).user_agent("dbx-changelog");

    if let Some(proxy_url) = crate::update::system_proxy_url() {
        let proxy = reqwest::Proxy::all(&proxy_url).map_err(|e| format!("Invalid system proxy URL: {e}"))?;
        builder = builder.proxy(proxy);
    }

    builder.build().map_err(|e| format!("Failed to create HTTP client: {e}"))
}

#[cfg(test)]
mod tests {
    use super::normalize_changelog_lang;

    #[test]
    fn normalizes_changelog_lang() {
        assert_eq!(normalize_changelog_lang("cn"), "cn");
        assert_eq!(normalize_changelog_lang("zh-CN"), "cn");
        assert_eq!(normalize_changelog_lang("zh-TW"), "cn");
        assert_eq!(normalize_changelog_lang("en"), "en");
        assert_eq!(normalize_changelog_lang("ja"), "en");
    }
}