//! `list [--kind issue|pr|both] [--state open|closed|all] [--assignee
//! <user>] [--author <user>] [--label <name>] [--limit N] [--page N]` —
//! list issues / PRs with filters. Pretty `#NNN [author] title` output by
//! default; `--json` for piping. `--limit` is the page size and `--page`
//! the 1-based page number — walk pages incrementally for a large result
//! set rather than pulling the whole population into one response.
//!
//! Mirrors Forgejo's `GET /repos/{owner}/{repo}/issues` query-string
//! filters one-for-one so the mental model carries over. Closes the
//! read-side curl-fallback gap (no boundary concerns —
//! every agent + the operator queries the issue tracker constantly).

use anyhow::Result;
use clap::{Args as ClapArgs, ValueEnum};
use forgejo_api::structs::{
    IssueListIssuesQuery, IssueListIssuesQueryState, IssueListIssuesQueryType,
};
use serde_json::Value;

use crate::client::Client;
use crate::verbs::print_json;

/// What kind of items to return. Maps onto Forgejo's `type` query
/// parameter: `issues` / `pulls`, or no filter at all for `both`
/// (Forgejo returns issues + PRs when `type` is absent — same slice
/// the forge UI's "Issues" tab shows without a type filter).
#[derive(Copy, Clone, Debug, ValueEnum)]
#[clap(rename_all = "kebab-case")]
pub enum Kind {
    /// Issues only (excludes PRs).
    Issue,
    /// Pull requests only.
    Pr,
    /// Issues + pull requests (default).
    Both,
}

impl Kind {
    fn query_type(self) -> Option<IssueListIssuesQueryType> {
        match self {
            Self::Issue => Some(IssueListIssuesQueryType::Issues),
            Self::Pr => Some(IssueListIssuesQueryType::Pulls),
            Self::Both => None,
        }
    }
}

/// State filter. Matches Forgejo's `state` query parameter
/// (`open` / `closed` / `all`).
#[derive(Copy, Clone, Debug, ValueEnum)]
#[clap(rename_all = "kebab-case")]
pub enum State {
    Open,
    Closed,
    All,
}

impl State {
    fn query_state(self) -> IssueListIssuesQueryState {
        match self {
            Self::Open => IssueListIssuesQueryState::Open,
            Self::Closed => IssueListIssuesQueryState::Closed,
            Self::All => IssueListIssuesQueryState::All,
        }
    }
}

#[derive(ClapArgs)]
pub struct Args {
    /// What to return: issues, PRs, or both (default: both).
    #[arg(long, value_enum, default_value_t = Kind::Both)]
    kind: Kind,
    /// Issue/PR state (default: open).
    #[arg(long, value_enum, default_value_t = State::Open)]
    state: State,
    /// Filter to items assigned to this user (single login).
    #[arg(long)]
    assignee: Option<String>,
    /// Filter to items authored by this user (single login).
    #[arg(long)]
    author: Option<String>,
    /// Filter to items mentioning this user.
    #[arg(long)]
    mention: Option<String>,
    /// Filter to items carrying any of these label names. Repeatable.
    #[arg(long = "label")]
    labels: Vec<String>,
    /// Page size — items per page (default: 30; forge's per-page cap,
    /// ~50, applies). Must be >= 1.
    #[arg(long, default_value_t = 30, value_parser = clap::value_parser!(u64).range(1..))]
    limit: u64,
    /// Page number to fetch (1-based, default 1). Combine with `--limit`
    /// to page through large result sets incrementally.
    #[arg(long, default_value_t = 1, value_parser = clap::value_parser!(u64).range(1..))]
    page: u64,
}

pub fn run(client: &Client, args: Args) -> Result<()> {
    let (owner, name) = client.owner_repo()?;
    let query = IssueListIssuesQuery {
        state: Some(args.state.query_state()),
        // The forge parses `labels` as a comma-separated list of names.
        labels: (!args.labels.is_empty()).then(|| args.labels.join(",")),
        q: None,
        r#type: args.kind.query_type(),
        milestones: None,
        since: None,
        before: None,
        created_by: args.author.clone().filter(|s| !s.is_empty()),
        assigned_by: args.assignee.clone().filter(|s| !s.is_empty()),
        mentioned_by: args.mention.clone().filter(|s| !s.is_empty()),
        sort: None,
    };
    let (_, issues) = client
        .api()
        .issue_list_issues(owner, name, query)
        .page(u32::try_from(args.page).unwrap_or(u32::MAX))
        .page_size(u32::try_from(args.limit).unwrap_or(u32::MAX))
        .send()?;
    let count = issues.len() as u64;
    let items = serde_json::to_value(issues)?;
    if client.json_mode() {
        return print_json(&items);
    }
    for item in items.as_array().into_iter().flatten() {
        print_row(item);
    }
    // When the returned page is exactly `--limit` items, more pages
    // may exist. Print a hint to stderr so the caller knows to fetch
    // the next page rather than assuming the result is complete. Only
    // fires on a full page — a short or empty page signals the end.
    if count == args.limit {
        eprintln!(
            "… {} shown (page {}); more results may exist — re-run with --page {} (or raise --limit).",
            args.limit,
            args.page,
            args.page + 1
        );
    }
    Ok(())
}

/// Render one issue/PR as a single `#NNN [author] title` line.
/// Defensive: missing fields drop to placeholders so a partial
/// response from a future API change still produces readable output
/// instead of panicking on `unwrap`.
fn print_row(item: &Value) {
    let number = item.get("number").and_then(Value::as_u64).unwrap_or(0);
    let title = item.get("title").and_then(Value::as_str).unwrap_or("");
    let author = item
        .get("user")
        .and_then(|u| u.get("login"))
        .and_then(Value::as_str)
        .unwrap_or("?");
    // Tag PRs visually so a mixed-kind result stays scannable. The
    // forge always populates `pull_request` but sets it to `null` for
    // issues; we check non-null specifically rather than just-present
    // (which would render every issue as a PR).
    let is_pr = item.get("pull_request").is_some_and(|v| !v.is_null());
    let kind = if is_pr { "PR" } else { "  " };
    println!("#{number:>4} {kind} [{author}] {title}");
}

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

    #[test]
    fn kind_query_types_match_forgejo_enum() {
        // The forge accepts only `issues` / `pulls` for the `type`
        // parameter (absent = both) — pin the mapping so a clap rename
        // doesn't silently start returning the wrong slice.
        assert_eq!(
            Kind::Issue.query_type(),
            Some(IssueListIssuesQueryType::Issues)
        );
        assert_eq!(Kind::Pr.query_type(), Some(IssueListIssuesQueryType::Pulls));
        assert_eq!(Kind::Both.query_type(), None);
    }

    #[test]
    fn state_query_states_match_forgejo_enum() {
        assert_eq!(State::Open.query_state(), IssueListIssuesQueryState::Open);
        assert_eq!(
            State::Closed.query_state(),
            IssueListIssuesQueryState::Closed
        );
        assert_eq!(State::All.query_state(), IssueListIssuesQueryState::All);
    }
}