use std::path::Path;

use crate::{

    errors::HgError,

    exit_codes,

    filepatterns::parse_pattern_file_contents,

    matchers::{

        AlwaysMatcher, DifferenceMatcher, IncludeMatcher, Matcher,

        NeverMatcher,

    },

    repo::Repo,

    requirements::NARROW_REQUIREMENT,

    sparse::{self, SparseConfigError, SparseWarning},

};

/// The file in .hg/store/ that indicates which paths exit in the store

const FILENAME: &str = "narrowspec";

/// The file in .hg/ that indicates which paths exit in the dirstate

const DIRSTATE_FILENAME: &str = "narrowspec.dirstate";

/// Pattern prefixes that are allowed in narrow patterns. This list MUST

/// only contain patterns that are fast and safe to evaluate. Keep in mind

/// that patterns are supplied by clients and executed on remote servers

/// as part of wire protocol commands. That means that changes to this

/// data structure influence the wire protocol and should not be taken

/// lightly - especially removals.

const VALID_PREFIXES: [&str; 2] = ["path:", "rootfilesin:"];

/// Return the matcher for the current narrow spec, and all configuration

/// warnings to display.

pub fn matcher(

    repo: &Repo,

) -> Result<(Box<dyn Matcher + Sync>, Vec<SparseWarning>), SparseConfigError> {

    let mut warnings = vec![];

    if !repo.requirements().contains(NARROW_REQUIREMENT) {

        return Ok((Box::new(AlwaysMatcher), warnings));

    }

    // Treat "narrowspec does not exist" the same as "narrowspec file exists

    // and is empty".

    let store_spec = repo.store_vfs().try_read(FILENAME)?.unwrap_or_default();

    let working_copy_spec = repo

        .hg_vfs()

        .try_read(DIRSTATE_FILENAME)?

        .unwrap_or_default();

    if store_spec != working_copy_spec {

        return Err(HgError::abort(

            exit_codes::STATE_ERROR,

            Some("run 'hg tracked --update-working-copy'".into()),

        )

        .into());

    }

    let config = sparse::parse_config(

        &store_spec,

        sparse::SparseConfigContext::Narrow,

    )?;

    warnings.extend(config.warnings);

    if !config.profiles.is_empty() {

        // TODO (from Python impl) maybe do something with profiles?

        return Err(SparseConfigError::IncludesInNarrow);

    }

    validate_patterns(&config.includes)?;

    validate_patterns(&config.excludes)?;

    if config.includes.is_empty() {

        return Ok((Box::new(NeverMatcher), warnings));

    }

    let (patterns, subwarnings) = parse_pattern_file_contents(

        &config.includes,

        Path::new(""),

        None,

        false,

    )?;

    warnings.extend(subwarnings.into_iter().map(From::from));

    let mut m: Box<dyn Matcher + Sync> =

        Box::new(IncludeMatcher::new(patterns)?);

    let (patterns, subwarnings) = parse_pattern_file_contents(

        &config.excludes,

        Path::new(""),

        None,

        false,

    )?;

    if !patterns.is_empty() {

        warnings.extend(subwarnings.into_iter().map(From::from));

        let exclude_matcher = Box::new(IncludeMatcher::new(patterns)?);

        m = Box::new(DifferenceMatcher::new(m, exclude_matcher));

    }

    Ok((m, warnings))

}

fn validate_patterns(patterns: &[u8]) -> Result<(), SparseConfigError> {

    for pattern in patterns.split(|c| *c == b'\n') {

        if pattern.is_empty() {

            continue;

        }

        for prefix in VALID_PREFIXES.iter() {

            if pattern.starts_with(prefix.as_bytes()) {

                return Ok(());

            }

        }

        return Err(SparseConfigError::InvalidNarrowPrefix(

            pattern.to_owned(),

        ));

    }

    Ok(())

}