aoc-runtime 0.6.0

//! Turning command line arguments into a concrete plan of work.
//!
//! Resolution is pure: it takes the parsed arguments, the configuration, a
//! directory and a clock, and produces a [`Plan`] whose variants carry exactly
//! what their handler needs. A mode that requires a language cannot be
//! constructed without one, so no downstream code has to re-check.

use crate::{
    cli::{Cli, Mode},
    config::Config,
    env::{Clock, is_december},
    language::Language,
    puzzle::{Day, Puzzle, Year},
    template::{Params, TemplateError},
};
use chrono::{Datelike, NaiveDate};
use std::path::{Path, PathBuf};

/// A fully resolved unit of work.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Plan {
    /// Build and run a solution, optionally submitting its answers.
    Run {
        /// The puzzle being solved.
        puzzle: Puzzle,
        /// The language the solution is written in.
        language: Language,
        /// The project directory.
        project: PathBuf,
        /// Whether answers should be submitted.
        submit: bool,
    },
    /// Scaffold a new solution.
    Init {
        /// The puzzle being solved.
        puzzle: Puzzle,
        /// The language to scaffold.
        language: Language,
        /// The project directory.
        project: PathBuf,
    },
    /// Print a project directory.
    Path {
        /// The project directory.
        project: PathBuf,
    },
    /// Open a project directory in the editor.
    Code {
        /// The project directory.
        project: PathBuf,
    },
    /// Print a puzzle URL.
    Url {
        /// The puzzle to link to.
        puzzle: Puzzle,
    },
}

/// Resolves arguments, the working directory and the clock into a [`Plan`].
///
/// Precedence for each value is: explicit argument, then whatever the working
/// directory reveals through the configured template, then a date-based
/// default.
///
/// # Errors
///
/// Returns [`ResolveError::LanguageRequired`] if the mode needs a language and
/// none could be determined, or [`ResolveError::Template`] if the template's
/// matcher cannot be compiled.
pub fn plan(
    cli: &Cli,
    config: &Config,
    cwd: &Path,
    clock: &dyn Clock,
) -> Result<Plan, ResolveError> {
    let today = clock.today();
    let detected = config.template.matcher()?.detect(cwd);

    let year = cli
        .year
        .and_then(Year::new)
        .or(detected.year)
        .unwrap_or_else(|| latest_available_year(today));

    let day = cli
        .day
        .and_then(Day::new)
        .or_else(|| detected.day.filter(|&day| year.has_day(day)))
        .unwrap_or_else(|| default_day(year, today));

    let puzzle = Puzzle::new(year, day).ok_or(ResolveError::DayOutOfRange { year, day })?;
    let language = cli.language.or(detected.language);

    if !cli.mode.needs_language() {
        return Ok(Plan::Url { puzzle });
    }

    let language = language.ok_or(ResolveError::LanguageRequired { mode: cli.mode })?;
    let project = config.template.render(Params {
        year,
        day,
        language,
    });

    Ok(match cli.mode {
        Mode::Run => Plan::Run {
            puzzle,
            language,
            project,
            submit: !cli.no_submit,
        },
        Mode::Init => Plan::Init {
            puzzle,
            language,
            project,
        },
        Mode::Path => Plan::Path { project },
        Mode::Code => Plan::Code { project },
        Mode::Url => Plan::Url { puzzle },
    })
}

/// The most recent event that has started on the given date.
///
/// Advent of Code begins on 1 December, so before December the current year's
/// event does not exist yet.
#[must_use]
pub fn latest_available_year(today: NaiveDate) -> Year {
    let year = today.year();
    let available = if is_december(today) { year } else { year - 1 };

    u16::try_from(available)
        .ok()
        .and_then(Year::new)
        .unwrap_or(Year::FIRST)
}

/// The day to use when none was given: today during the event, otherwise the
/// first puzzle.
///
/// Today is clamped to the end of `year`'s event, which is day 12 from
/// [`Year::FIRST_SHORT`] on.
#[must_use]
pub fn default_day(year: Year, today: NaiveDate) -> Day {
    if is_december(today) {
        Day::clamped(year, today.day())
    } else {
        Day::FIRST
    }
}

/// Errors produced while resolving a plan.
#[derive(Debug, thiserror::Error)]
pub enum ResolveError {
    /// The mode needs a language and none was given or detected.
    #[error(
        "a language is required for `{mode}` - pass --language, or run from a \
         directory the template can resolve"
    )]
    LanguageRequired {
        /// The mode that needs a language.
        mode: Mode,
    },
    /// The requested day is past the end of the requested event.
    #[error("{year} has no day {day} - that event ends on day {}", .year.last_day())]
    DayOutOfRange {
        /// The event the day was requested in.
        year: Year,
        /// The requested day.
        day: Day,
    },
    /// The template could not be compiled into a matcher.
    #[error("could not build a matcher from the configured template")]
    Template(#[from] TemplateError),
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::env::{Env, FixedClock};
    use clap::Parser as _;

    fn env(cwd: &str) -> Env {
        Env {
            home: PathBuf::from("/home/tester"),
            config_dir: PathBuf::from("/home/tester/.config/aoc"),
            config_file: PathBuf::from("/home/tester/.config/aoc/config.yaml"),
            state_dir: PathBuf::from("/home/tester/.local/state/aoc"),
            cwd: PathBuf::from(cwd),
            session_cookie: None,
        }
    }

    fn config() -> Config {
        let (config, _) = Config::from_yaml(
            "template_path: \"/root/{{year}}/day{{pad day}}/{{language}}\"",
            &env("/"),
        )
        .expect("config should load");
        config
    }

    fn cli(args: &[&str]) -> Cli {
        let mut command_line = vec!["aoc"];
        command_line.extend_from_slice(args);
        Cli::try_parse_from(command_line).expect("arguments should parse")
    }

    fn date(year: i32, month: u32, day: u32) -> NaiveDate {
        NaiveDate::from_ymd_opt(year, month, day).expect("valid date")
    }

    fn year(year: u16) -> Year {
        Year::new(year).expect("valid year")
    }

    fn resolve(args: &[&str], cwd: &str, today: NaiveDate) -> Result<Plan, ResolveError> {
        plan(&cli(args), &config(), Path::new(cwd), &FixedClock(today))
    }

    fn puzzle_of(plan: &Plan) -> Option<Puzzle> {
        match plan {
            Plan::Run { puzzle, .. } | Plan::Init { puzzle, .. } | Plan::Url { puzzle } => {
                Some(*puzzle)
            }
            Plan::Path { .. } | Plan::Code { .. } => None,
        }
    }

    fn project_of(plan: &Plan) -> Option<&Path> {
        match plan {
            Plan::Run { project, .. }
            | Plan::Init { project, .. }
            | Plan::Path { project }
            | Plan::Code { project } => Some(project),
            Plan::Url { .. } => None,
        }
    }

    #[test]
    fn the_most_recent_event_depends_on_the_month() {
        assert_eq!(latest_available_year(date(2024, 12, 1)).get(), 2024);
        assert_eq!(latest_available_year(date(2024, 12, 31)).get(), 2024);
        assert_eq!(latest_available_year(date(2024, 11, 30)).get(), 2023);
        assert_eq!(latest_available_year(date(2025, 1, 1)).get(), 2024);
    }

    #[test]
    fn the_default_day_is_today_during_the_event() {
        assert_eq!(default_day(year(2024), date(2024, 12, 1)).get(), 1);
        assert_eq!(default_day(year(2024), date(2024, 12, 14)).get(), 14);
        assert_eq!(default_day(year(2024), date(2024, 12, 25)).get(), 25);
    }

    #[test]
    fn the_default_day_is_clamped_after_the_event_ends() {
        for day in 26..=31 {
            assert_eq!(
                default_day(year(2024), date(2024, 12, day)).get(),
                25,
                "december {day}"
            );
        }
    }

    #[test]
    fn the_default_day_is_clamped_to_a_shortened_event() {
        for day in 13..=31 {
            assert_eq!(
                default_day(year(2025), date(2025, 12, day)).get(),
                12,
                "december {day}"
            );
        }
    }

    #[test]
    fn the_default_day_is_the_first_outside_december() {
        assert_eq!(default_day(year(2024), date(2024, 1, 20)).get(), 1);
        assert_eq!(default_day(year(2024), date(2024, 11, 30)).get(), 1);
    }

    #[test]
    fn explicit_arguments_win_over_everything() {
        let plan = resolve(
            &["-y", "2019", "-d", "3", "-l", "java", "path"],
            "/root/2024/day07/rust",
            date(2024, 12, 14),
        )
        .expect("plan should resolve");

        assert_eq!(project_of(&plan), Some(Path::new("/root/2019/day03/java")));
    }

    #[test]
    fn the_working_directory_wins_over_date_defaults() {
        let plan = resolve(&["path"], "/root/2019/day03/java", date(2024, 12, 14))
            .expect("plan should resolve");

        assert_eq!(project_of(&plan), Some(Path::new("/root/2019/day03/java")));
    }

    #[test]
    fn date_defaults_apply_when_nothing_else_does() {
        let plan = resolve(&["-l", "rust", "path"], "/elsewhere", date(2024, 12, 14))
            .expect("plan should resolve");

        assert_eq!(project_of(&plan), Some(Path::new("/root/2024/day14/rust")));
    }

    #[test]
    fn a_partial_directory_fills_the_rest_from_defaults() {
        let plan = resolve(&["-l", "rust", "path"], "/root/2019", date(2024, 12, 14))
            .expect("plan should resolve");

        assert_eq!(project_of(&plan), Some(Path::new("/root/2019/day14/rust")));
    }

    #[test]
    fn an_explicit_day_the_event_never_had_is_an_error() {
        let error = resolve(
            &["-y", "2025", "-d", "20", "url"],
            "/elsewhere",
            date(2025, 12, 20),
        )
        .expect_err("2025 ends on day 12");

        assert!(
            matches!(error, ResolveError::DayOutOfRange { .. }),
            "{error:?}"
        );
        assert!(error.to_string().contains("2025 has no day 20"), "{error}");
    }

    #[test]
    fn a_detected_day_the_event_never_had_falls_back_to_the_default() {
        let plan = resolve(&["path"], "/root/2025/day20/rust", date(2025, 12, 5))
            .expect("plan should resolve");

        assert_eq!(project_of(&plan), Some(Path::new("/root/2025/day05/rust")));
    }

    #[test]
    fn a_shortened_event_still_accepts_its_own_days() {
        let plan = resolve(
            &["-y", "2025", "-d", "12", "url"],
            "/elsewhere",
            date(2026, 1, 1),
        )
        .expect("plan should resolve");

        assert_eq!(
            puzzle_of(&plan).map(Puzzle::url).as_deref(),
            Some("https://adventofcode.com/2025/day/12")
        );
    }

    #[test]
    fn url_needs_no_language() {
        let plan = resolve(&["url"], "/elsewhere", date(2024, 12, 5)).expect("plan should resolve");

        assert_eq!(
            plan,
            Plan::Url {
                puzzle: puzzle_of(&plan).expect("url carries a puzzle")
            }
        );
        assert_eq!(
            puzzle_of(&plan).map(Puzzle::url).as_deref(),
            Some("https://adventofcode.com/2024/day/5")
        );
    }

    #[test]
    fn other_modes_require_a_language() {
        for mode in ["run", "init", "path", "code"] {
            let error = resolve(&[mode], "/elsewhere", date(2024, 12, 5))
                .expect_err("language is required");

            assert!(
                matches!(error, ResolveError::LanguageRequired { .. }),
                "{mode}: {error:?}"
            );
            assert!(error.to_string().contains(mode), "{error}");
        }
    }

    #[test]
    fn run_submits_unless_told_otherwise() {
        let submitting = resolve(
            &["-l", "rust", "run"],
            "/root/2024/day07/rust",
            date(2024, 12, 7),
        )
        .expect("plan should resolve");
        let quiet = resolve(
            &["-l", "rust", "--no-submit", "run"],
            "/root/2024/day07/rust",
            date(2024, 12, 7),
        )
        .expect("plan should resolve");

        assert!(matches!(submitting, Plan::Run { submit: true, .. }));
        assert!(matches!(quiet, Plan::Run { submit: false, .. }));
    }

    #[test]
    fn each_mode_produces_its_own_plan() {
        let cwd = "/root/2024/day07/rust";
        let today = date(2024, 12, 7);

        assert!(matches!(
            resolve(&["run"], cwd, today),
            Ok(Plan::Run { .. })
        ));
        assert!(matches!(
            resolve(&["init"], cwd, today),
            Ok(Plan::Init { .. })
        ));
        assert!(matches!(
            resolve(&["path"], cwd, today),
            Ok(Plan::Path { .. })
        ));
        assert!(matches!(
            resolve(&["code"], cwd, today),
            Ok(Plan::Code { .. })
        ));
        assert!(matches!(
            resolve(&["url"], cwd, today),
            Ok(Plan::Url { .. })
        ));
    }
}