//! Driving the `pimsync` binary.
//!
//! pimsync handles the CalDAV and WebCal legs, mirroring each remote into a local
//! vdir. It is invoked one-shot: its own daemon would race the reconciler over the
//! same files, so scheduling belongs to calcalist.

use std::fmt;
use std::fs;
use std::io;
use std::os::fd::AsFd;
use std::path::{Path, PathBuf};
use std::process::{Command, Output, Stdio};

use thiserror::Error;

use crate::config::{Config, Endpoint, EndpointKind};

pub const BINARY: &str = "pimsync";

/// The oldest pimsync this build generates configuration for. `discover`'s
/// output format is undocumented and changed between 0.5.9 and 0.5.11, and
/// `parse_discovery` only understands the newer shape.
pub const MIN_VERSION: Version = Version {
    major: 0,
    minor: 5,
    patch: 11,
};

/// The first release this build makes no claim about. pimsync is pre-1.0 and
/// its config syntax may change between minor releases, so a series is
/// admitted only once read: 0.6.0 renamed `auth` to `auth_method`, which costs
/// nothing here — generated storages carry `username` and `password`, never
/// `auth` — and left `discover`'s output word for word as it was.
pub const NEXT_UNKNOWN_VERSION: Version = Version {
    major: 0,
    minor: 7,
    patch: 0,
};

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub struct Version {
    pub major: u64,
    pub minor: u64,
    pub patch: u64,
}

impl fmt::Display for Version {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}.{}.{}", self.major, self.minor, self.patch)
    }
}

impl Version {
    pub fn is_supported(&self) -> bool {
        *self >= MIN_VERSION && *self < NEXT_UNKNOWN_VERSION
    }

    /// Parses the `pimsync 0.5.11` line printed by `pimsync version`.
    fn parse(output: &str) -> Option<Self> {
        let field = output.split_whitespace().nth(1)?;
        let mut parts = field.split('.');
        Some(Version {
            major: number(parts.next()?)?,
            minor: number(parts.next()?)?,
            patch: number(parts.next().unwrap_or("0"))?,
        })
    }
}

/// The leading digits of one version component. pimsync takes its version from
/// `git describe`, so a build off a tag carries a suffix — `0.6.0-1-ga08ee3c`
/// — which belongs to no number.
fn number(part: &str) -> Option<u64> {
    part.split(|c: char| !c.is_ascii_digit())
        .next()?
        .parse()
        .ok()
}

#[derive(Debug, Error)]
pub enum PimsyncError {
    #[error("`{BINARY}` was not found on PATH; install pimsync {MIN_VERSION} or newer")]
    NotFound,
    #[error("could not run `{BINARY}`: {0}")]
    Spawn(#[source] io::Error),
    #[error("`{BINARY} version` failed: {0}")]
    Failed(String),
    #[error("could not read a version out of `{0}`")]
    Unparseable(String),
    #[error("could not write {path}: {source}")]
    Write {
        path: std::path::PathBuf,
        #[source]
        source: io::Error,
    },
    #[error("`{BINARY} {command}` failed: {message}")]
    Command { command: String, message: String },
    #[error(
        "endpoint `{endpoint}` has url `{url}`, which names no calendar collection; it must point at the calendar itself, not at the server root"
    )]
    UrlHasNoCollection { endpoint: String, url: String },
}

/// Asks the installed pimsync for its version.
pub fn probe() -> Result<Version, PimsyncError> {
    let output = Command::new(BINARY)
        .arg("version")
        .output()
        .map_err(spawn_error)?;
    if !output.status.success() {
        return Err(PimsyncError::Failed(
            String::from_utf8_lossy(&output.stderr).trim().to_string(),
        ));
    }
    let text = String::from_utf8_lossy(&output.stdout);
    let line = text.lines().next().unwrap_or_default().trim();
    Version::parse(line).ok_or_else(|| PimsyncError::Unparseable(line.to_string()))
}

/// Name of the single local storage every pair mirrors into. pimsync allows one
/// storage to take part in several pairs, so one declaration serves all of them.
const LOCAL_STORAGE: &str = "local";

pub fn config_path(state_dir: &Path) -> PathBuf {
    state_dir.join("pimsync.conf")
}

pub(crate) fn status_path(state_dir: &Path) -> PathBuf {
    state_dir.join("pimsync-status")
}

/// Which way a generated configuration lets items travel.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Direction {
    /// The ordinary cycle: remote and local converge on each other.
    Both,
    /// Remote to local only, for `--dry-run`. pimsync writes nothing to any
    /// server in this mode — but it does delete local items the remote has
    /// never seen, so it is only ever pointed at a throwaway copy of the vdirs.
    PullOnly,
}

/// Builds a pimsync configuration covering every CalDAV and WebCal endpoint.
///
/// Google endpoints are absent by design: pimsync has no REST storage, and its
/// CalDAV storage speaks only HTTP Basic auth, which Google's endpoint has
/// rejected since March 2025. calcalist syncs those itself.
pub fn generate_for(
    config: &Config,
    state_dir: &Path,
    direction: Direction,
) -> Result<String, PimsyncError> {
    let mut out = String::new();
    out.push_str("# Generated by calcalist. Edits here are overwritten on every sync.\n\n");
    out.push_str(&format!(
        "status_path {}\n\n",
        quote(&status_path(state_dir).display().to_string())
    ));
    out.push_str(&format!(
        "storage {LOCAL_STORAGE} {{\n\ttype vdir/icalendar\n\tpath {}\n\tfileext ics\n}}\n",
        quote(&crate::sync::vdir_root(state_dir).display().to_string())
    ));

    for endpoint in &config.endpoints {
        match &endpoint.kind {
            EndpointKind::Caldav { .. } => out.push_str(&caldav_pair(endpoint, direction)?),
            EndpointKind::Webcal { url, url_command } => {
                out.push_str(&webcal_pair(
                    endpoint,
                    url.as_deref(),
                    url_command.as_deref(),
                ));
            }
            // Handled by calcalist's own Google module.
            EndpointKind::Google { .. } => {}
        }
    }
    Ok(out)
}

fn caldav_pair(endpoint: &Endpoint, direction: Direction) -> Result<String, PimsyncError> {
    let EndpointKind::Caldav {
        url,
        username,
        secret_command,
    } = &endpoint.kind
    else {
        unreachable!("caller matched on Caldav")
    };
    let (base, href) =
        split_collection_url(url).ok_or_else(|| PimsyncError::UrlHasNoCollection {
            endpoint: endpoint.id.clone(),
            url: url.clone(),
        })?;

    let id = &endpoint.id;
    let mut block = format!(
        "\nstorage {id}_remote {{\n\ttype caldav\n\turl {}\n\tdiscovery collections\n\tusername {}\n",
        quote(&base),
        quote(username)
    );
    if let Some(command) = secret_command {
        // Secrets never live in the portable config, so pimsync runs the same
        // command calcalist would to fetch them.
        block.push_str(&format!("\tpassword {{\n\t\tshell {command}\n\t}}\n"));
    }
    block.push_str("}\n");

    // The remote is storage_a, so a concurrent server-side change wins over a
    // local one calcalist has not yet reconciled. Nothing is lost: the next
    // cycle sees the server's version and decides properly.
    let resolution = match direction {
        // `one_way` never produces a conflict, so there is nothing to resolve.
        Direction::PullOnly => "\tone_way\n",
        Direction::Both => "\tconflict_resolution keep a\n",
    };
    block.push_str(&format!(
        "\npair {id} {{\n\tstorage_a {id}_remote\n\tstorage_b {LOCAL_STORAGE}\n\
         \tcollection {{\n\t\talias {id}\n\t\thref_a {}\n\t\tid_b {id}\n\t}}\n\
         {resolution}\ton_empty skip\n\ton_delete skip\n}}\n",
        quote(&href)
    ));
    Ok(block)
}

fn webcal_pair(endpoint: &Endpoint, url: Option<&str>, url_command: Option<&str>) -> String {
    let id = &endpoint.id;
    // A feed URL that is itself a credential is fetched by command, the same way
    // passwords are, so it never appears in either configuration file.
    let url_directive = match (url, url_command) {
        (_, Some(command)) => format!("\turl {{\n\t\tshell {command}\n\t}}\n"),
        (Some(url), None) => format!("\turl {}\n", quote(url)),
        (None, None) => String::new(),
    };
    // No `read_only` directive here: pimsync 0.5.11 documents it as applying to
    // every storage type, but rejects it on a webcal storage with a bare "Could
    // not parse file". It is redundant regardless — webcal is read-only by type,
    // and `one_way` already fixes the direction.
    format!(
        "\nstorage {id}_remote {{\n\ttype webcal\n{url_directive}\tcollection_id {id}\n}}\n\
         \npair {id} {{\n\tstorage_a {id}_remote\n\tstorage_b {LOCAL_STORAGE}\n\
         \tcollection {{\n\t\talias {id}\n\t\tid_a {id}\n\t\tid_b {id}\n\t}}\n\
         \tone_way\n\ton_empty skip\n\ton_delete skip\n}}\n"
    )
}

/// Splits a calendar URL into the container to enumerate and the collection's
/// own path.
///
/// pimsync identifies a collection either by an id taken from a URL segment or
/// by its exact path. The path is used here, so a calendar whose last segment
/// happens to match another's cannot be confused for it.
fn split_collection_url(url: &str) -> Option<(String, String)> {
    let authority_start = url.find("://")? + 3;
    let path_start = authority_start + url[authority_start..].find('/')?;
    let segments: Vec<&str> = url[path_start..]
        .split('/')
        .filter(|segment| !segment.is_empty())
        .collect();
    let (_, parents) = segments.split_last()?;

    let href = format!("/{}/", segments.join("/"));
    let base = match parents {
        [] => format!("{}/", &url[..path_start]),
        parents => format!("{}/{}/", &url[..path_start], parents.join("/")),
    };
    Some((base, href))
}

/// pimsync accepts quoted values, which keeps paths with spaces intact.
fn quote(value: &str) -> String {
    format!("\"{}\"", value.replace('\\', "\\\\").replace('"', "\\\""))
}

/// Writes the generated configuration, returning its path.
pub fn write_config(config: &Config, state_dir: &Path) -> Result<PathBuf, PimsyncError> {
    write_config_for(config, state_dir, Direction::Both)
}

pub fn write_config_for(
    config: &Config,
    state_dir: &Path,
    direction: Direction,
) -> Result<PathBuf, PimsyncError> {
    let path = config_path(state_dir);
    let text = generate_for(config, state_dir, direction)?;
    fs::create_dir_all(status_path(state_dir)).map_err(|source| PimsyncError::Write {
        path: status_path(state_dir),
        source,
    })?;
    fs::write(&path, text).map_err(|source| PimsyncError::Write {
        path: path.clone(),
        source,
    })?;
    Ok(path)
}

/// The storage name the probe config gives the server being examined. Parsing
/// anchors on it, because pimsync discovers *both* storages in a pair and prints
/// their collections under one heading each.
const PROBE_REMOTE: &str = "probe_remote";

/// One collection found on a server.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Collection {
    /// The path pimsync reported, e.g. `/calendars/me/work/`.
    pub href: String,
    /// A usable endpoint id, taken from the last meaningful path segment.
    pub id: String,
}

/// Asks pimsync which calendars a server offers.
///
/// `url` is a container to enumerate — an account or principal path — rather
/// than a single calendar, so `split_collection_url` does not apply here.
///
/// `pimsync discover` is documented as informational and as not altering
/// pimsync's state, so pointing it at a server the user has not configured yet
/// is safe. The probe configuration it needs is written under a name of its own
/// so it can never be mistaken for, or overwrite, the generated `pimsync.conf`.
pub fn discover(
    state_dir: &Path,
    url: &str,
    username: &str,
    secret_command: Option<&str>,
) -> Result<Vec<Collection>, PimsyncError> {
    let config_path = state_dir.join("discover.conf");
    let scratch = state_dir.join("discover-vdir");
    fs::create_dir_all(&scratch).map_err(|source| PimsyncError::Write {
        path: scratch.clone(),
        source,
    })?;
    fs::write(
        &config_path,
        probe_config(state_dir, &scratch, url, username, secret_command),
    )
    .map_err(|source| PimsyncError::Write {
        path: config_path.clone(),
        source,
    })?;

    let output = Command::new(BINARY)
        .arg("-c")
        .arg(&config_path)
        .arg("discover")
        .output()
        .map_err(spawn_error)?;

    // Everything, including the failures, comes back on stdout.
    let text = String::from_utf8_lossy(&output.stdout).into_owned();
    let _ = fs::remove_dir_all(&scratch);
    if !output.status.success() {
        return Err(PimsyncError::Command {
            command: "discover".to_string(),
            message: strip_ansi(&text).trim().to_string(),
        });
    }
    Ok(parse_discovery(&text))
}

fn probe_config(
    state_dir: &Path,
    scratch: &Path,
    url: &str,
    username: &str,
    secret_command: Option<&str>,
) -> String {
    let password = match secret_command {
        Some(command) => format!("\tpassword {{\n\t\tshell {command}\n\t}}\n"),
        None => String::new(),
    };
    format!(
        "# Generated by `calcalist discover`. Rewritten on every run.\n\
         status_path {}\n\n\
         storage local {{\n\ttype vdir/icalendar\n\tpath {}\n\tfileext ics\n}}\n\n\
         storage {PROBE_REMOTE} {{\n\ttype caldav\n\turl {}\n\tdiscovery collections\n\
         \tusername {}\n{password}}}\n\n\
         pair probe {{\n\tstorage_a {PROBE_REMOTE}\n\tstorage_b local\n\
         \tcollections from a\n}}\n",
        quote(&state_dir.join("discover-status").display().to_string()),
        quote(&scratch.display().to_string()),
        quote(url),
        quote(username),
    )
}

/// Reads the collections out of `pimsync discover` output.
///
/// The format is not documented, so this was established against a real server
/// and is deliberately forgiving. The one thing it must get right: a pair has
/// two storages and pimsync reports both, so `Found` lines are only taken after
/// the heading naming the server. Otherwise the scratch directory's own
/// contents would be offered as if they were the user's calendars.
fn parse_discovery(output: &str) -> Vec<Collection> {
    let mut collections = Vec::new();
    let mut in_remote = false;
    for line in output.lines() {
        let line = strip_ansi(line);
        let line = line.trim();
        if line.starts_with("==>") {
            in_remote = line.contains(PROBE_REMOTE);
            continue;
        }
        let Some(href) = line.strip_prefix("Found ") else {
            continue;
        };
        let href = href.trim();
        if !in_remote || href.is_empty() {
            continue;
        }
        collections.push(Collection {
            id: collection_id(href),
            href: href.to_string(),
        });
    }
    collections
}

/// A plausible endpoint id: the last non-empty path segment, restricted to
/// characters that are unambiguous in a configuration file.
fn collection_id(href: &str) -> String {
    let segment = href
        .rsplit('/')
        .find(|segment| !segment.is_empty())
        .unwrap_or(href);
    let id: String = segment
        .chars()
        .map(|ch| match ch {
            'a'..='z' | '0'..='9' | '-' | '_' => ch,
            'A'..='Z' => ch.to_ascii_lowercase(),
            _ => '-',
        })
        .collect();
    let id = id.trim_matches('-').to_string();
    if id.is_empty() { "calendar".into() } else { id }
}

/// Removes ANSI colour, which pimsync emits even when its output is a pipe and
/// even under NO_COLOR.
fn strip_ansi(text: &str) -> String {
    let mut out = String::with_capacity(text.len());
    let mut chars = text.chars();
    while let Some(ch) = chars.next() {
        if ch != '\u{1b}' {
            out.push(ch);
            continue;
        }
        // Skip up to and including the terminating letter of the escape.
        for next in chars.by_ref() {
            if next.is_ascii_alphabetic() {
                break;
            }
        }
    }
    out
}

/// Runs one pimsync cycle.
///
/// Deliberately one-shot: `pimsync daemon` would write the same vdirs the
/// reconciler is reading, so calcalist owns the scheduling instead.
/// A cycle is minutes of network work, and pimsync's per-item progress is the
/// only sign it is alive. Capturing that output left `sync` looking wedged for
/// the whole run and then printing nothing, so it goes straight to the terminal.
pub fn sync(config_path: &Path) -> Result<(), PimsyncError> {
    let status = invocation(config_path, "sync")
        .stdout(progress_stream()?)
        .stderr(Stdio::inherit())
        .status()
        .map_err(spawn_error)?;
    if status.success() {
        return Ok(());
    }
    // The detail has already been printed as it happened; repeating it here
    // would only put a second copy under the report.
    Err(PimsyncError::Command {
        command: "sync".to_string(),
        message: format!("exited with {status}"),
    })
}

/// Validates the generated configuration and the storages it names.
///
/// Captured rather than streamed: `doctor` reads the message to tell a config
/// it must fix from a server it cannot reach, and prints its own summary.
pub fn check(config_path: &Path) -> Result<(), PimsyncError> {
    let output = invocation(config_path, "check")
        .output()
        .map_err(spawn_error)?;
    if output.status.success() {
        return Ok(());
    }
    let message = diagnostics(&output);
    Err(PimsyncError::Command {
        command: "check".to_string(),
        message: if message.is_empty() {
            format!("exited with {}", output.status)
        } else {
            message
        },
    })
}

/// `pimsync -c <config> <command>`, with stdin closed so that a secret helper
/// reaching for a terminal fails outright rather than waiting on one forever.
fn invocation(config_path: &Path, command: &str) -> Command {
    let mut process = Command::new(BINARY);
    process
        .arg("-c")
        .arg(config_path)
        .arg(command)
        .stdin(Stdio::null());
    process
}

/// pimsync's progress, routed to our stderr so that stdout carries only the
/// report and stays worth piping.
fn progress_stream() -> Result<Stdio, PimsyncError> {
    io::stderr()
        .as_fd()
        .try_clone_to_owned()
        .map(Stdio::from)
        .map_err(PimsyncError::Spawn)
}

fn spawn_error(error: io::Error) -> PimsyncError {
    if error.kind() == io::ErrorKind::NotFound {
        PimsyncError::NotFound
    } else {
        PimsyncError::Spawn(error)
    }
}

/// What a failed run had to say for itself.
///
/// Both streams are read: pimsync reports execution errors on stderr but puts
/// parse failures on stdout, and which one carries the reason is not knowable
/// from here.
fn diagnostics(output: &Output) -> String {
    let streams = [&output.stderr, &output.stdout];
    let said: Vec<String> = streams
        .iter()
        .map(|stream| String::from_utf8_lossy(stream).trim().to_string())
        .filter(|text| !text.is_empty())
        .collect();
    said.join("\n")
}

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

    use crate::config::Config;
    use std::path::Path;

    const CONFIG: &str = r#"
version = 1

[[endpoint]]
id = "work"
type = "caldav"
url = "https://dav.example.com/dav/calendars/user/me/work/"
username = "me@example.com"
secret_command = "pass show example/caldav"

[[endpoint]]
id = "gcal"
type = "google"
calendar_id = "me@example.com"
client_id = "abc.apps.googleusercontent.com"

[[endpoint]]
id = "holidays"
type = "webcal"
url = "https://example.org/holidays.ics"
"#;

    /// The text of one `storage`/`pair` block, so assertions do not accidentally
    /// match a directive belonging to a different block.
    fn block<'a>(text: &'a str, opening: &str) -> &'a str {
        let start = text.find(opening).expect("block should be present");
        let rest = &text[start..];
        rest.find("\n}\n").map_or(rest, |end| &rest[..end])
    }

    fn generated() -> String {
        let config: Config = toml::from_str(CONFIG).expect("config should parse");
        generate_for(&config, Path::new("/var/state/calcalist"), Direction::Both)
            .expect("generation should succeed")
    }

    #[test]
    fn declares_one_local_storage_for_every_pair() {
        let text = generated();
        assert_eq!(text.matches("storage local {").count(), 1);
        assert!(text.contains("path \"/var/state/calcalist/vdir\""));
        assert!(text.contains("status_path \"/var/state/calcalist/pimsync-status\""));
    }

    /// pimsync cannot authenticate to Google at all, so it must not be asked to.
    #[test]
    fn google_endpoints_are_left_out_entirely() {
        let text = generated();
        assert!(!text.contains("gcal"), "google endpoint leaked into {text}");
    }

    #[test]
    fn a_caldav_endpoint_becomes_a_bidirectional_pair() {
        let text = generated();
        assert!(text.contains("storage work_remote {"));
        assert!(text.contains("type caldav"));
        // The container is enumerated, and the calendar picked out by exact path.
        assert!(text.contains("url \"https://dav.example.com/dav/calendars/user/me/\""));
        assert!(text.contains("href_a \"/dav/calendars/user/me/work/\""));
        assert!(text.contains("id_b work"));
        assert!(
            !block(&text, "pair work {").contains("one_way"),
            "caldav pairs must stay bidirectional"
        );
    }

    /// Secrets stay out of the portable config; pimsync fetches them the same way.
    #[test]
    fn secrets_are_fetched_by_command_not_embedded() {
        let text = generated();
        assert!(text.contains("password {"));
        assert!(text.contains("shell pass show example/caldav"));
    }

    #[test]
    fn a_feed_becomes_a_one_way_read_only_pair() {
        let text = generated();
        assert!(text.contains("type webcal"));
        assert!(text.contains("one_way"));
        // pimsync 0.5.11 rejects `read_only` on a webcal storage despite
        // documenting it for all storage types.
        assert!(!block(&text, "storage holidays_remote {").contains("read_only"));
        assert!(text.contains("collection_id holidays"));
    }

    /// Both guards against a failed pull being mirrored as a mass deletion.
    #[test]
    fn every_pair_carries_the_deletion_guards() {
        let text = generated();
        let pairs = text.matches("\npair ").count();
        assert_eq!(pairs, 2);
        assert_eq!(text.matches("on_empty skip").count(), pairs);
        assert_eq!(text.matches("on_delete skip").count(), pairs);
    }

    /// A feed whose URL is itself a credential — Google's secret iCal address —
    /// must be fetched by command, never written into either config file.
    #[test]
    fn a_secret_feed_url_is_fetched_by_command() {
        let config: Config = toml::from_str(
            r#"
version = 1

[[endpoint]]
id = "gcal-feed"
type = "webcal"
url_command = "secret-tool lookup service calcalist account gcal-ics"
"#,
        )
        .expect("config should parse");
        let text = generate_for(&config, Path::new("/var/state/calcalist"), Direction::Both)
            .expect("generate");

        assert!(text.contains("url {"));
        assert!(text.contains("shell secret-tool lookup service calcalist account gcal-ics"));
        assert!(!text.contains("https://"), "no literal URL should appear");
    }

    #[test]
    fn splits_a_calendar_url_into_container_and_path() {
        assert_eq!(
            split_collection_url("https://dav.example.com/dav/calendars/user/me/work/"),
            Some((
                "https://dav.example.com/dav/calendars/user/me/".into(),
                "/dav/calendars/user/me/work/".into()
            ))
        );
        // A trailing slash is optional.
        assert_eq!(
            split_collection_url("https://dav.example.com/calendars/work"),
            Some((
                "https://dav.example.com/calendars/".into(),
                "/calendars/work/".into()
            ))
        );
        // A single segment leaves the root as the container.
        assert_eq!(
            split_collection_url("https://dav.example.com/work/"),
            Some(("https://dav.example.com/".into(), "/work/".into()))
        );
    }

    /// A bare server root names no calendar, so it must be rejected rather than
    /// guessed at.
    #[test]
    fn a_url_without_a_collection_is_refused() {
        assert_eq!(split_collection_url("https://dav.example.com/"), None);
        assert_eq!(split_collection_url("https://dav.example.com"), None);
    }

    #[test]
    fn parses_the_version_line() {
        assert_eq!(
            Version::parse("pimsync 0.5.11"),
            Some(Version {
                major: 0,
                minor: 5,
                patch: 11
            })
        );
    }

    #[test]
    fn tolerates_a_two_component_version() {
        assert_eq!(
            Version::parse("pimsync 1.2"),
            Some(Version {
                major: 1,
                minor: 2,
                patch: 0
            })
        );
    }

    /// pimsync built from a checkout rather than a tag reports `git describe`'s
    /// suffix, which must not swallow the patch number.
    #[test]
    fn tolerates_a_describe_suffix() {
        assert_eq!(
            Version::parse("pimsync 0.6.0-1-ga08ee3c"),
            Some(Version {
                major: 0,
                minor: 6,
                patch: 0
            })
        );
    }

    #[test]
    fn rejects_unparseable_output() {
        assert_eq!(Version::parse("pimsync"), None);
        assert_eq!(Version::parse("pimsync unreleased"), None);
    }

    #[test]
    fn the_read_series_are_accepted() {
        let floor = Version {
            major: 0,
            minor: 5,
            patch: 11,
        };
        let read = Version {
            major: 0,
            minor: 6,
            patch: 0,
        };
        let unread = Version {
            major: 0,
            minor: 7,
            patch: 0,
        };
        assert!(floor.is_supported());
        assert!(read.is_supported());
        assert!(!unread.is_supported());
    }

    #[test]
    fn a_patch_older_than_the_floor_is_rejected() {
        // discover's output format changed between 0.5.9 and 0.5.11; older
        // patches within the otherwise-supported minor series are refused.
        let too_old = Version {
            major: 0,
            minor: 5,
            patch: 9,
        };
        assert!(!too_old.is_supported());
    }

    /// Established against a real server: everything arrives on stdout, the
    /// headings are colour-coded even through a pipe, and both storages of the
    /// pair are reported.
    const DISCOVERY: &str = "\u{1b}[1m\u{1b}[32m==>\u{1b}[0m Discovering collections in local\u{2026}\n\
         Found leftover-one\n\
         Found leftover-two\n\
         \u{1b}[1m\u{1b}[32m==>\u{1b}[0m Discovering collections in probe_remote\u{2026}\n\
         Found /calendars/me/work/\n\
         Found /calendars/me/Private Stuff/\n";

    /// The trap: pimsync reports the scratch directory's contents too, and
    /// offering those as the user's calendars would be nonsense.
    #[test]
    fn only_the_servers_collections_are_taken() {
        let found = parse_discovery(DISCOVERY);

        assert_eq!(
            found.iter().map(|c| c.href.as_str()).collect::<Vec<_>>(),
            vec!["/calendars/me/work/", "/calendars/me/Private Stuff/"]
        );
    }

    #[test]
    fn an_id_is_taken_from_the_last_segment() {
        let found = parse_discovery(DISCOVERY);
        assert_eq!(found[0].id, "work");
        // Spaces and capitals cannot appear in an id used as a routing marker.
        assert_eq!(found[1].id, "private-stuff");
    }

    #[test]
    fn a_server_offering_nothing_yields_nothing() {
        let empty = "\u{1b}[1m==>\u{1b}[0m Discovering collections in probe_remote\u{2026}\n";
        assert!(parse_discovery(empty).is_empty());
    }

    /// A failure is reported in place of the collections, so nothing is found.
    #[test]
    fn an_unreachable_server_yields_nothing() {
        let failed = "\u{1b}[1m==>\u{1b}[0m Discovering collections in probe_remote\u{2026}\n\
             input/output error: client error executing request: client error (Connect)\n";
        assert!(parse_discovery(failed).is_empty());
    }

    #[test]
    fn colour_is_stripped_from_headings() {
        assert_eq!(
            strip_ansi("\u{1b}[1m\u{1b}[32m==>\u{1b}[0m Discovering"),
            "==> Discovering"
        );
    }

    /// The probe must never be mistaken for the real configuration, and must
    /// name the storage the parser anchors on.
    #[test]
    fn the_probe_config_is_separate_and_parseable() {
        let text = probe_config(
            Path::new("/var/state/calcalist"),
            Path::new("/var/state/calcalist/discover-vdir"),
            "https://dav.example.com/calendars/me/",
            "me@example.com",
            Some("secret-tool lookup service dav"),
        );
        assert!(
            text.contains(&format!("storage {PROBE_REMOTE} {{")),
            "{text}"
        );
        assert!(text.contains("collections from a"), "{text}");
        assert!(text.contains("discovery collections"), "{text}");
        assert!(
            text.contains("shell secret-tool lookup service dav"),
            "{text}"
        );
        // Its status path is its own, so a probe cannot disturb a real sync.
        assert!(text.contains("discover-status"), "{text}");
    }

    #[test]
    fn a_server_needing_no_password_gets_no_password_directive() {
        let text = probe_config(
            Path::new("/var/state/calcalist"),
            Path::new("/tmp/scratch"),
            "https://dav.example.com/calendars/me/",
            "me",
            None,
        );
        assert!(!text.contains("password"), "{text}");
    }
}