//! `pr-create --title <t> --head <branch> [--base <b>] [body sources]
//! [--draft] [--push] [--remote <name>] [repo]` — create a PR. Prints
//! the PR URL.
//!
//! With `--push` the local `--head` branch is pushed to `--remote`
//! (default `forge`) before the API call, and forgejo's post-push
//! "Create a new pull request" / "Visit the existing pull request"
//! hint block is filtered out of git's stderr (we print the canonical
//! URL ourselves once the API returns). Other git stderr passes
//! through. Default behaviour is unchanged: no push unless asked.
//! Adds the auto-push path per operator decision (opt-in
//! flag).
//!
//! With `--agit` the PR is opened via Forgejo's `AGit` flow instead of
//! the REST API: the current `HEAD` is pushed to `refs/for/<base>/<topic>`
//! (run from inside a cloned repo), which opens a PR even when the user
//! is a read-only collaborator who can't push branches. Re-running with
//! the same `--topic` updates the open PR. This is the path agents use
//! to contribute to `internal/knowledge`; pair it with `hive-forge clone`.
//! A multi-line `--body` can't ride as a git push option (the wire
//! protocol forbids newlines there), so it's pushed title-only and the
//! body is set on the resulting PR via a REST PATCH.

use std::process::{Command, Stdio};

use anyhow::{Context, Result};
use clap::Args as ClapArgs;
use forgejo_api::structs::{CreatePullRequestOption, EditIssueOption, IssueLabelsOption};
use serde_json::json;

use crate::body;
use crate::client::{Client, index};
use crate::verbs::labels;

#[derive(ClapArgs)]
pub struct Args {
    /// PR title.
    #[arg(long)]
    title: String,
    /// Head branch. Not required (and ignored) in `--agit` mode, which
    /// pushes the current `HEAD`.
    #[arg(long, required_unless_present = "agit")]
    head: Option<String>,
    /// Base branch (default: main).
    #[arg(long, default_value = "main")]
    base: String,
    /// Inline body text.
    #[arg(long, conflicts_with = "body_file")]
    body: Option<String>,
    /// Read body from a file. `-` means stdin.
    #[arg(long = "body-file")]
    body_file: Option<String>,
    /// Open as draft. Ignored in `--agit` mode.
    #[arg(long)]
    draft: bool,
    /// Push the local `--head` branch to `--remote` before creating the PR.
    #[arg(long)]
    push: bool,
    /// Remote to push to (default: `forge`, or `origin` in `--agit` mode).
    #[arg(long)]
    remote: Option<String>,
    /// Open the PR via Forgejo's `AGit` flow instead of pushing a branch —
    /// works for read-only collaborators. Run from inside a cloned repo.
    #[arg(long)]
    agit: bool,
    /// `AGit` topic — groups repeated pushes into one PR (re-run with the
    /// same topic to update it). Defaults to the branch name. Only
    /// meaningful with `--agit`.
    #[arg(long)]
    topic: Option<String>,
    /// Label name to attach, repeatable (e.g. `--label area/ops --label
    /// type/bug`). Same spelling `labels add` accepts. In `--agit` mode
    /// this is applied as a follow-up call once the PR number is known
    /// (the `AGit` push itself has no label field), so it's silently
    /// skipped if the PR URL couldn't be parsed back out of the push
    /// output — same fallback as the deferred multi-line body.
    #[arg(long = "label")]
    labels: Vec<String>,
}

/// # Errors
///
/// Propagates any I/O error from the body input (`--body-file`,
/// stdin) or the `--push` shellout to git, any transport error from
/// the Forgejo REST call (network unreachable, 4xx/5xx response,
/// token missing/invalid), and any I/O error from writing the PR
/// URL to stdout.
pub fn run(client: &Client, args: Args) -> Result<()> {
    let body = body::resolve(args.body.as_deref(), args.body_file.as_deref())?.unwrap_or_default();
    if args.agit {
        return agit_create(client, &args, &body);
    }
    // Normal REST flow. `--head` is required (clap enforces it unless
    // `--agit`), so unwrap is safe here.
    let head = args
        .head
        .as_deref()
        .expect("clap requires --head unless --agit");
    let remote = args.remote.as_deref().unwrap_or("forge");
    if args.push {
        push_branch(remote, head)?;
    }
    let (owner, name) = client.owner_repo()?;
    let label_ids = if args.labels.is_empty() {
        None
    } else {
        let all = labels::repo_labels(client)?;
        Some(labels::resolve_ids(&all, &args.labels))
    };
    // Note: Forgejo's CreatePullRequestOption has no `draft` /
    // `allow_maintainer_edit` fields (verified against the instance's
    // swagger) — the raw client used to send both and the server
    // silently dropped them, so omitting them here changes nothing.
    let payload = CreatePullRequestOption {
        assignee: None,
        assignees: None,
        base: Some(args.base.clone()),
        body: Some(body),
        due_date: None,
        head: Some(head.to_owned()),
        labels: label_ids,
        milestone: None,
        title: Some(args.title.clone()),
    };
    let resp = client
        .api()
        .repo_create_pull_request(owner, name, payload)
        .send()?;
    if let Some(url) = resp.html_url {
        println!("{url}");
    }
    Ok(())
}

/// Open (or update) a PR via Forgejo's `AGit` flow: push the current
/// `HEAD` to `refs/for/<base>/<topic>` with the PR metadata carried as
/// push options. Run from inside the cloned repo's working tree.
/// `force-push=true` lets a re-run with the same topic UPDATE the open
/// PR (the new commit branches from base's tip, which the forge sees as
/// non-fast-forward against the existing PR head and rejects without it).
///
/// The git wire protocol forbids newline characters in push options, so
/// a multi-line `description=` would make the push fail outright. A
/// single-line body still rides along as a push option (it's guaranteed
/// to land even if we can't parse the PR URL back out); a multi-line
/// body is pushed title-only and then set on the resulting PR via a REST
/// PATCH, mirroring the manual `pr-create --title …` + `issue-edit
/// --body-file` two-step.
fn agit_create(client: &Client, args: &Args, body: &str) -> Result<()> {
    let remote = args.remote.as_deref().unwrap_or("origin");
    let topic = match &args.topic {
        Some(t) => t.clone(),
        None => current_branch().unwrap_or_else(|| "contribution".to_owned()),
    };
    // A body with any newline can't be a push option; defer it to a REST
    // PATCH after the push. A single-line body is safe inline.
    let inline_body = !body.is_empty() && !body.contains('\n');
    let deferred_body = !body.is_empty() && body.contains('\n');
    let refspec = format!("HEAD:refs/for/{}/{topic}", args.base);
    let mut push_args = vec![
        "push".to_owned(),
        remote.to_owned(),
        refspec,
        "-o".to_owned(),
        format!("topic={topic}"),
        "-o".to_owned(),
        format!("title={}", args.title),
        "-o".to_owned(),
        "force-push=true".to_owned(),
    ];
    if inline_body {
        push_args.push("-o".to_owned());
        push_args.push(format!("description={body}"));
    }
    let arg_refs: Vec<&str> = push_args.iter().map(String::as_str).collect();
    let output = Command::new("git")
        .args(&arg_refs)
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .output()
        .with_context(|| format!("failed to spawn `git push {remote}` (AGit)"))?;
    let stderr = String::from_utf8_lossy(&output.stderr);
    if !output.status.success() {
        anyhow::bail!("`git push {remote}` (AGit) failed:\n{stderr}");
    }
    let Some(url) = parse_pr_url(&stderr) else {
        // Push landed but no PR URL in the sideband — surface the raw
        // remote output so the caller can find the link themselves.
        eprint!("{stderr}");
        if deferred_body {
            eprintln!(
                "warning: multi-line body NOT set — PR URL not parsed, so it could \
                 not be PATCHed. Set it manually: hive-forge issue-edit <pr#> --body-file -"
            );
        }
        println!(
            "AGit push to refs/for/{}/{topic} succeeded (PR URL not parsed from output above)",
            args.base
        );
        return Ok(());
    };
    if deferred_body {
        if let Some(number) = pr_number_from_url(&url) {
            let (owner, name) = client.owner_repo()?;
            let payload = EditIssueOption {
                assignee: None,
                assignees: None,
                body: Some(body.to_owned()),
                due_date: None,
                milestone: None,
                r#ref: None,
                state: None,
                title: None,
                unset_due_date: None,
                updated_at: None,
            };
            client
                .api()
                .issue_edit_issue(owner, name, index(number)?, payload)
                .send()
                .with_context(|| format!("set body on AGit PR #{number}"))?;
        } else {
            eprintln!(
                "warning: multi-line body NOT set — could not parse PR number from {url}. \
                 Set it manually: hive-forge issue-edit <pr#> --body-file -"
            );
        }
    }
    if !args.labels.is_empty() {
        apply_agit_labels(client, &args.labels, &url)?;
    }
    println!("{url}");
    Ok(())
}

/// Follow-up label-add call for an `--agit`-created PR: the `AGit` push
/// itself has no label field, so this mirrors the deferred-body PATCH —
/// resolve the PR number back out of the parsed URL, then add the
/// resolved label ids via the same `issue_add_label` call `labels add`
/// uses. Warns (doesn't fail the whole command) if the PR number
/// couldn't be parsed, same fallback as the deferred body.
fn apply_agit_labels(client: &Client, names: &[String], url: &str) -> Result<()> {
    let Some(number) = pr_number_from_url(url) else {
        eprintln!(
            "warning: --label NOT applied — could not parse PR number from {url}. \
             Set it manually: hive-forge labels <pr#> add <name>..."
        );
        return Ok(());
    };
    let (owner, name) = client.owner_repo()?;
    let all = labels::repo_labels(client)?;
    let ids: Vec<serde_json::Value> = labels::resolve_ids(&all, names)
        .into_iter()
        .map(|id| json!(id))
        .collect();
    client
        .api()
        .issue_add_label(
            owner,
            name,
            index(number)?,
            IssueLabelsOption {
                labels: Some(ids),
                updated_at: None,
            },
        )
        .send()
        .with_context(|| format!("set labels on AGit PR #{number}"))?;
    Ok(())
}

/// Extract the PR index from a Forgejo PR URL (`…/pulls/<n>`). Returns
/// `None` if the last path segment isn't a number.
fn pr_number_from_url(url: &str) -> Option<u64> {
    url.trim_end_matches('/')
        .rsplit('/')
        .next()
        .and_then(|seg| seg.parse().ok())
}

/// Current git branch name (`git rev-parse --abbrev-ref HEAD`), or
/// `None` on detached HEAD / error.
fn current_branch() -> Option<String> {
    let out = Command::new("git")
        .args(["rev-parse", "--abbrev-ref", "HEAD"])
        .output()
        .ok()?;
    if !out.status.success() {
        return None;
    }
    let name = String::from_utf8_lossy(&out.stdout).trim().to_owned();
    if name.is_empty() || name == "HEAD" {
        None
    } else {
        Some(name)
    }
}

/// Scan `git push` stderr for the PR URL. The forge prints it on a
/// `remote:` sideband line following the "Create a new pull request" /
/// "Visit the existing pull request" opener; rather than match the
/// exact phrasing, we pick the first `remote:` URL containing `/pulls/`.
fn parse_pr_url(stderr: &str) -> Option<String> {
    for line in stderr.lines() {
        let Some(content) = line.trim_start().strip_prefix("remote:") else {
            continue;
        };
        let content = content.trim_start();
        if let Some(start) = content.find("http") {
            let url = content[start..]
                .split_whitespace()
                .next()
                .unwrap_or_default();
            if url.contains("/pulls/") {
                return Some(url.to_owned());
            }
        }
    }
    None
}

/// Run `git push <remote> <head>` and pass stderr through with the
/// post-push PR-hint block filtered out. On failure, bubble up
/// git's full stderr so the user sees why the push didn't land.
fn push_branch(remote: &str, head: &str) -> Result<()> {
    let output = Command::new("git")
        .args(["push", remote, head])
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .output()
        .with_context(|| format!("failed to spawn `git push {remote} {head}`"))?;
    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        anyhow::bail!("`git push {remote} {head}` failed:\n{stderr}");
    }
    let stderr = String::from_utf8_lossy(&output.stderr);
    let filtered = strip_pr_hint_block(&stderr);
    if !filtered.is_empty() {
        eprint!("{filtered}");
    }
    Ok(())
}

/// Drop the 3-line PR-hint block forgejo appends after push:
///
/// ```text
/// remote: Create a new pull request for 'BRANCH':
/// remote:   http://.../compare/...
/// remote:
/// ```
///
/// or the existing-PR variant. Other `remote:` lines (and everything
/// else) pass through unchanged.
fn strip_pr_hint_block(stderr: &str) -> String {
    let mut out = String::with_capacity(stderr.len());
    let mut lines = stderr.split_inclusive('\n').peekable();
    while let Some(line) = lines.next() {
        if is_pr_hint_opener(line) {
            // Eat up to two follow-on `remote:` lines (URL + blank).
            for _ in 0..2 {
                if lines.peek().is_some_and(|next| is_remote_line(next)) {
                    lines.next();
                } else {
                    break;
                }
            }
            continue;
        }
        out.push_str(line);
    }
    out
}

fn remote_content(line: &str) -> Option<&str> {
    line.trim_end_matches(['\n', '\r'])
        .trim_start()
        .strip_prefix("remote:")
        .map(str::trim_start)
}

fn is_remote_line(line: &str) -> bool {
    remote_content(line).is_some()
}

fn is_pr_hint_opener(line: &str) -> bool {
    remote_content(line).is_some_and(|c| {
        c.starts_with("Create a new pull request")
            || c.starts_with("Visit the existing pull request")
    })
}

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

    #[test]
    fn agit_parse_pr_url_picks_pulls_link() {
        let stderr = "\
remote: Visit the existing pull request:\n\
remote:   http://forge.example/internal/knowledge/pulls/2\n\
remote: \n\
To http://localhost:3000/internal/knowledge.git\n\
 * [new reference]   HEAD -> refs/pull/2/head\n";
        assert_eq!(
            parse_pr_url(stderr).as_deref(),
            Some("http://forge.example/internal/knowledge/pulls/2")
        );
    }

    #[test]
    fn agit_parse_pr_url_handles_created_phrasing() {
        let stderr = "\
remote: Create a new pull request:\n\
remote:   http://forge.example/internal/knowledge/pulls/7\n";
        assert_eq!(
            parse_pr_url(stderr).as_deref(),
            Some("http://forge.example/internal/knowledge/pulls/7")
        );
    }

    #[test]
    fn agit_parse_pr_url_none_when_absent() {
        assert_eq!(parse_pr_url("To http://localhost:3000/x/y.git\n"), None);
    }

    #[test]
    fn pr_number_parses_trailing_index() {
        assert_eq!(
            pr_number_from_url("http://forge.example/internal/knowledge/pulls/42"),
            Some(42)
        );
        // tolerant of a trailing slash
        assert_eq!(
            pr_number_from_url("http://forge.example/org/repo/pulls/7/"),
            Some(7)
        );
        // not a number → None (caller falls back to the manual-edit hint)
        assert_eq!(
            pr_number_from_url("http://forge.example/org/repo/pulls/"),
            None
        );
        assert_eq!(
            pr_number_from_url("http://forge.example/org/repo/compare"),
            None
        );
    }

    #[test]
    fn strips_create_pr_hint_block() {
        let stderr = "\
remote: Create a new pull request for 'feat/foo':\n\
remote:   http://localhost:3000/hyperhive/hyperhive/compare/main...feat/foo\n\
remote: \n\
To http://localhost:3000/hyperhive/hyperhive.git\n\
 * [new branch]      feat/foo -> feat/foo\n";
        let cleaned = strip_pr_hint_block(stderr);
        assert!(!cleaned.contains("Create a new pull request"));
        assert!(!cleaned.contains("compare/main"));
        assert!(cleaned.contains("[new branch]"));
        assert!(cleaned.contains("To http://localhost:3000/hyperhive/hyperhive.git"));
    }

    #[test]
    fn strips_visit_existing_pr_hint_block() {
        let stderr = "\
remote: Visit the existing pull request:\n\
remote:   http://localhost:3000/hyperhive/hyperhive/pulls/527 merges into main\n\
remote: \n\
To http://localhost:3000/hyperhive/hyperhive.git\n\
   55430bb..bdfd437  feat/519-unify-prompts -> feat/519-unify-prompts\n";
        let cleaned = strip_pr_hint_block(stderr);
        assert!(!cleaned.contains("Visit the existing pull request"));
        assert!(!cleaned.contains("/pulls/527"));
        assert!(cleaned.contains("55430bb..bdfd437"));
    }

    #[test]
    fn passes_unrelated_remote_lines_through() {
        // Real-world: pre-receive hooks, lint output, anything the
        // forge or hooks decide to print via the sideband. Only the
        // PR-hint block opener triggers the skip.
        let stderr = "\
remote: pre-receive hook says: looks fine\n\
remote: actions queued: 2\n\
To http://localhost:3000/hyperhive/hyperhive.git\n";
        let cleaned = strip_pr_hint_block(stderr);
        assert_eq!(cleaned, stderr);
    }

    #[test]
    fn handles_empty_stderr() {
        assert_eq!(strip_pr_hint_block(""), "");
    }

    #[test]
    fn stops_eating_after_two_followups() {
        // Defensive: if the forge ever drops the trailing blank
        // `remote:` line, we still only eat what we expect (URL line)
        // and pass the next line through.
        let stderr = "\
remote: Create a new pull request for 'feat/foo':\n\
remote:   http://localhost:3000/.../compare/...\n\
To http://localhost:3000/hyperhive/hyperhive.git\n\
 * [new branch]      feat/foo -> feat/foo\n";
        let cleaned = strip_pr_hint_block(stderr);
        assert!(!cleaned.contains("Create a new pull request"));
        assert!(!cleaned.contains("/compare/"));
        assert!(cleaned.contains("To http://"));
        assert!(cleaned.contains("[new branch]"));
    }

    #[test]
    fn opener_detector_recognises_both_phrasings() {
        assert!(is_pr_hint_opener(
            "remote: Create a new pull request for 'x':\n"
        ));
        assert!(is_pr_hint_opener(
            "remote: Visit the existing pull request:\n"
        ));
        assert!(!is_pr_hint_opener("remote: some other thing\n"));
        assert!(!is_pr_hint_opener("To http://example.com\n"));
        // Trailing-CRLF safety on windows-cloned forge clones.
        assert!(is_pr_hint_opener(
            "remote: Create a new pull request for 'x':\r\n"
        ));
    }
}