use crate::github::GithubEndpoints;
use crate::source::Endpoints;
use anyhow::{Context, Result, bail};
use regex::Regex;
use serde::Deserialize;

/// Resolves the latest release tag for `repo` on whichever service
/// `endpoints` points at.
pub fn latest_release(
    client: &reqwest::blocking::Client,
    endpoints: &Endpoints,
    repo: &str,
) -> Result<String> {
    match endpoints {
        Endpoints::Github(github) => latest_github_release(client, github, repo),
        Endpoints::Forgejo { api } => latest_forgejo_release(client, api, repo),
    }
}

/// Resolves the latest release tag for `repo` on a Forgejo/Gitea instance.
///
/// One call, unlike GitHub's feed-then-confirm dance below: Forgejo's
/// `releases/latest` already returns only the newest non-draft,
/// non-prerelease *release object*, so a stray tag with no release behind
/// it (GitHub's scaleway-cli `-dbg1` problem) can't be returned.
pub fn latest_forgejo_release(
    client: &reqwest::blocking::Client,
    api: &str,
    repo: &str,
) -> Result<String> {
    #[derive(Deserialize)]
    struct Latest {
        tag_name: String,
    }

    let url = format!("{api}/repos/{repo}/releases/latest");
    let response = client.get(&url).send()?;
    // Forgejo answers 404 both for an unknown repo and for one with no
    // releases yet — the common state for a project's very first release.
    if response.status() == reqwest::StatusCode::NOT_FOUND {
        bail!("no published release found at {url} (repo missing, or nothing released yet)");
    }
    let latest: Latest = response
        .error_for_status()
        .with_context(|| format!("fetching latest release from {url}"))?
        .json()?;
    Ok(latest.tag_name)
}

/// Resolves the latest release tag for `repo` via its public Atom feed.
///
/// Deliberately not a full XML parse: the feed lists entries newest-first,
/// and each `<link rel="alternate" .../releases/tag/<tag>"/>` is matched
/// in document order. Revisit with a real XML parser if GitHub's feed
/// shape ever changes.
///
/// The feed can list a tag newer than any tag with a real Release object
/// behind it — observed on scaleway/scaleway-cli, which pushes a
/// `vX.Y.Z-dbg1` tag (no corresponding Release; `releases/tags/<tag>`
/// 404s) right after each real release, and that tag sorts newest in the
/// feed. So each candidate is confirmed against the releases API in feed
/// order, returning the first that actually resolves.
pub fn latest_github_release(
    client: &reqwest::blocking::Client,
    endpoints: &GithubEndpoints,
    repo: &str,
) -> Result<String> {
    let url = format!("{}/{repo}/releases.atom", endpoints.web);
    let body = client.get(&url).send()?.error_for_status()?.text()?;

    let re = Regex::new(r#"releases/tag/([^"]+)""#)?;
    let mut candidates = re
        .captures_iter(&body)
        .map(|caps| caps[1].to_string())
        .peekable();
    if candidates.peek().is_none() {
        bail!("no release tag found in {url}");
    }

    for tag in candidates {
        let release_url = format!("{}/repos/{repo}/releases/tags/{tag}", endpoints.api);
        if client.get(&release_url).send()?.status().is_success() {
            return Ok(tag);
        }
    }
    bail!("no release tag in {url} resolved to a real release via the API")
}

/// Strips a leading `v` from a release tag, e.g. `v2.62.0` -> `2.62.0`.
///
/// Some projects (uv) tag releases with the bare version and use it
/// verbatim in asset filenames; others (scaleway-cli) tag `vX.Y.Z` but
/// still use the bare version in filenames. This is the version string
/// substituted into `{version}` placeholders in `asset_pattern` /
/// `checksum_asset_pattern`, not the tag used for API/attestation calls.
pub fn version_from_tag(tag: &str) -> &str {
    tag.strip_prefix('v').unwrap_or(tag)
}

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

    #[test]
    fn version_from_tag_strips_leading_v() {
        assert_eq!(version_from_tag("v2.62.0"), "2.62.0");
    }

    #[test]
    fn version_from_tag_leaves_bare_version_unchanged() {
        assert_eq!(version_from_tag("0.12.15"), "0.12.15");
    }

    fn atom_feed(tags: &[&str]) -> String {
        let entries: String = tags
            .iter()
            .map(|t| {
                format!(r#"<link rel="alternate" href="https://github.com/o/r/releases/tag/{t}"/>"#)
            })
            .collect();
        format!("<feed>{entries}</feed>")
    }

    #[test]
    fn latest_github_release_skips_tags_with_no_real_release() {
        let mut server = mockito::Server::new();
        let endpoints = GithubEndpoints {
            web: server.url(),
            api: server.url(),
        };

        // Mirrors the real scaleway-cli case: newest feed entry (a -dbg1
        // tag) has no Release object behind it and 404s.
        let _feed = server
            .mock("GET", "/o/r/releases.atom")
            .with_status(200)
            .with_body(atom_feed(&["v2.62.0-dbg1", "v2.62.0"]))
            .create();
        let _missing = server
            .mock("GET", "/repos/o/r/releases/tags/v2.62.0-dbg1")
            .with_status(404)
            .create();
        let _real = server
            .mock("GET", "/repos/o/r/releases/tags/v2.62.0")
            .with_status(200)
            .with_body("{}")
            .create();

        let client = reqwest::blocking::Client::new();
        let tag = latest_github_release(&client, &endpoints, "o/r").unwrap();
        assert_eq!(tag, "v2.62.0");
    }

    #[test]
    fn latest_github_release_errors_when_feed_has_no_tags() {
        let mut server = mockito::Server::new();
        let endpoints = GithubEndpoints {
            web: server.url(),
            api: server.url(),
        };
        let _feed = server
            .mock("GET", "/o/r/releases.atom")
            .with_status(200)
            .with_body("<feed></feed>")
            .create();

        let client = reqwest::blocking::Client::new();
        let err = latest_github_release(&client, &endpoints, "o/r").unwrap_err();
        assert!(err.to_string().contains("no release tag found"));
    }

    #[test]
    fn latest_github_release_errors_when_no_candidate_resolves() {
        let mut server = mockito::Server::new();
        let endpoints = GithubEndpoints {
            web: server.url(),
            api: server.url(),
        };
        let _feed = server
            .mock("GET", "/o/r/releases.atom")
            .with_status(200)
            .with_body(atom_feed(&["v1.0.0-dbg1"]))
            .create();
        let _missing = server
            .mock("GET", "/repos/o/r/releases/tags/v1.0.0-dbg1")
            .with_status(404)
            .create();

        let client = reqwest::blocking::Client::new();
        let err = latest_github_release(&client, &endpoints, "o/r").unwrap_err();
        assert!(err.to_string().contains("resolved to a real release"));
    }

    #[test]
    fn latest_forgejo_release_returns_tag_name() {
        let mut server = mockito::Server::new();
        let _latest = server
            .mock("GET", "/repos/o/r/releases/latest")
            .with_status(200)
            .with_body(r#"{"tag_name": "v0.1.0", "assets": []}"#)
            .create();

        let client = reqwest::blocking::Client::new();
        let tag = latest_forgejo_release(&client, &server.url(), "o/r").unwrap();
        assert_eq!(tag, "v0.1.0");
    }

    #[test]
    fn latest_forgejo_release_names_the_no_releases_case() {
        let mut server = mockito::Server::new();
        let _latest = server
            .mock("GET", "/repos/o/r/releases/latest")
            .with_status(404)
            .create();

        let client = reqwest::blocking::Client::new();
        let err = latest_forgejo_release(&client, &server.url(), "o/r").unwrap_err();
        assert!(err.to_string().contains("no published release"));
    }

    #[test]
    fn latest_forgejo_release_surfaces_server_errors() {
        let mut server = mockito::Server::new();
        let _latest = server
            .mock("GET", "/repos/o/r/releases/latest")
            .with_status(500)
            .create();

        let client = reqwest::blocking::Client::new();
        let err = latest_forgejo_release(&client, &server.url(), "o/r").unwrap_err();
        assert!(err.to_string().contains("fetching latest release"));
    }

    #[test]
    fn latest_release_dispatches_on_endpoint_kind() {
        let mut server = mockito::Server::new();
        let _forgejo = server
            .mock("GET", "/repos/o/r/releases/latest")
            .with_status(200)
            .with_body(r#"{"tag_name": "v2.0.0"}"#)
            .create();
        let _feed = server
            .mock("GET", "/o/r/releases.atom")
            .with_body(atom_feed(&["v1.0.0"]))
            .create();
        let _release = server
            .mock("GET", "/repos/o/r/releases/tags/v1.0.0")
            .with_status(200)
            .with_body("{}")
            .create();

        let client = reqwest::blocking::Client::new();
        let forgejo = Endpoints::Forgejo { api: server.url() };
        assert_eq!(latest_release(&client, &forgejo, "o/r").unwrap(), "v2.0.0");

        let github = Endpoints::Github(GithubEndpoints {
            web: server.url(),
            api: server.url(),
        });
        assert_eq!(latest_release(&client, &github, "o/r").unwrap(), "v1.0.0");
    }
}