use std::{collections::HashSet, path::Path};

use format_bytes::{write_bytes, DisplayBytes};

use crate::{
    errors::HgError,
    filepatterns::parse_pattern_file_contents,
    matchers::{
        AlwaysMatcher, DifferenceMatcher, IncludeMatcher, Matcher,
        UnionMatcher,
    },
    operations::cat,
    repo::Repo,
    requirements::SPARSE_REQUIREMENT,
    utils::{hg_path::HgPath, SliceExt},
    IgnorePattern, PatternError, PatternFileWarning, PatternSyntax, Revision,
    NULL_REVISION,
};

/// Command which is triggering the config read
#[derive(Copy, Clone, Debug)]
pub enum SparseConfigContext {
    Sparse,
    Narrow,
}

impl DisplayBytes for SparseConfigContext {
    fn display_bytes(
        &self,
        output: &mut dyn std::io::Write,
    ) -> std::io::Result<()> {
        match self {
            SparseConfigContext::Sparse => write_bytes!(output, b"sparse"),
            SparseConfigContext::Narrow => write_bytes!(output, b"narrow"),
        }
    }
}

/// Possible warnings when reading sparse configuration
#[derive(Debug, derive_more::From)]
pub enum SparseWarning {
    /// Warns about improper paths that start with "/"
    RootWarning {
        context: SparseConfigContext,
        line: Vec<u8>,
    },
    /// Warns about a profile missing from the given changelog revision
    ProfileNotFound { profile: Vec<u8>, rev: Revision },
    #[from]
    Pattern(PatternFileWarning),
}

/// Parsed sparse config
#[derive(Debug, Default)]
pub struct SparseConfig {
    // Line-separated
    includes: Vec<u8>,
    // Line-separated
    excludes: Vec<u8>,
    profiles: HashSet<Vec<u8>>,
    warnings: Vec<SparseWarning>,
}

/// All possible errors when reading sparse config
#[derive(Debug, derive_more::From)]
pub enum SparseConfigError {
    IncludesAfterExcludes {
        context: SparseConfigContext,
    },
    EntryOutsideSection {
        context: SparseConfigContext,
        line: Vec<u8>,
    },
    #[from]
    HgError(HgError),
    #[from]
    PatternError(PatternError),
}

/// Parse sparse config file content.
fn parse_config(
    raw: &[u8],
    context: SparseConfigContext,
) -> Result<SparseConfig, SparseConfigError> {
    let mut includes = vec![];
    let mut excludes = vec![];
    let mut profiles = HashSet::new();
    let mut warnings = vec![];

    #[derive(PartialEq, Eq)]
    enum Current {
        Includes,
        Excludes,
        None,
    };

    let mut current = Current::None;
    let mut in_section = false;

    for line in raw.split(|c| *c == b'\n') {
        let line = line.trim();
        if line.is_empty() || line[0] == b'#' {
            // empty or comment line, skip
            continue;
        }
        if line.starts_with(b"%include ") {
            let profile = line[b"%include ".len()..].trim();
            if !profile.is_empty() {
                profiles.insert(profile.into());
            }
        } else if line == b"[include]" {
            if in_section && current == Current::Includes {
                return Err(SparseConfigError::IncludesAfterExcludes {
                    context,
                });
            }
            in_section = true;
            current = Current::Includes;
            continue;
        } else if line == b"[exclude]" {
            in_section = true;
            current = Current::Excludes;
        } else {
            if current == Current::None {
                return Err(SparseConfigError::EntryOutsideSection {
                    context,
                    line: line.into(),
                });
            }
            if line.trim().starts_with(b"/") {
                warnings.push(SparseWarning::RootWarning {
                    context,
                    line: line.into(),
                });
                continue;
            }
            match current {
                Current::Includes => {
                    includes.push(b'\n');
                    includes.extend(line.iter());
                }
                Current::Excludes => {
                    excludes.push(b'\n');
                    excludes.extend(line.iter());
                }
                Current::None => unreachable!(),
            }
        }
    }

    Ok(SparseConfig {
        includes,
        excludes,
        profiles,
        warnings,
    })
}

fn read_temporary_includes(
    repo: &Repo,
) -> Result<Vec<Vec<u8>>, SparseConfigError> {
    let raw = repo.hg_vfs().try_read("tempsparse")?.unwrap_or(vec![]);
    if raw.is_empty() {
        return Ok(vec![]);
    }
    Ok(raw.split(|c| *c == b'\n').map(ToOwned::to_owned).collect())
}

/// Obtain sparse checkout patterns for the given revision
fn patterns_for_rev(
    repo: &Repo,
    rev: Revision,
) -> Result<Option<SparseConfig>, SparseConfigError> {
    if !repo.has_sparse() {
        return Ok(None);
    }
    let raw = repo.hg_vfs().try_read("sparse")?.unwrap_or(vec![]);

    if raw.is_empty() {
        return Ok(None);
    }

    let mut config = parse_config(&raw, SparseConfigContext::Sparse)?;

    if !config.profiles.is_empty() {
        let mut profiles: Vec<Vec<u8>> = config.profiles.into_iter().collect();
        let mut visited = HashSet::new();

        while let Some(profile) = profiles.pop() {
            if visited.contains(&profile) {
                continue;
            }
            visited.insert(profile.to_owned());

            let output =
                cat(repo, &rev.to_string(), vec![HgPath::new(&profile)])
                    .map_err(|_| {
                        HgError::corrupted(format!(
                            "dirstate points to non-existent parent node"
                        ))
                    })?;
            if output.results.is_empty() {
                config.warnings.push(SparseWarning::ProfileNotFound {
                    profile: profile.to_owned(),
                    rev,
                })
            }

            let subconfig = parse_config(
                &output.results[0].1,
                SparseConfigContext::Sparse,
            )?;
            if !subconfig.includes.is_empty() {
                config.includes.push(b'\n');
                config.includes.extend(&subconfig.includes);
            }
            if !subconfig.includes.is_empty() {
                config.includes.push(b'\n');
                config.excludes.extend(&subconfig.excludes);
            }
            config.warnings.extend(subconfig.warnings.into_iter());
            profiles.extend(subconfig.profiles.into_iter());
        }

        config.profiles = visited;
    }

    if !config.includes.is_empty() {
        config.includes.extend(b"\n.hg*");
    }

    Ok(Some(config))
}

/// Obtain a matcher for sparse working directories.
pub fn matcher(
    repo: &Repo,
) -> Result<(Box<dyn Matcher + Sync>, Vec<SparseWarning>), SparseConfigError> {
    let mut warnings = vec![];
    if !repo.requirements().contains(SPARSE_REQUIREMENT) {
        return Ok((Box::new(AlwaysMatcher), warnings));
    }

    let parents = repo.dirstate_parents()?;
    let mut revs = vec![];
    let p1_rev =
        repo.changelog()?
            .rev_from_node(parents.p1.into())
            .map_err(|_| {
                HgError::corrupted(format!(
                    "dirstate points to non-existent parent node"
                ))
            })?;
    if p1_rev != NULL_REVISION {
        revs.push(p1_rev)
    }
    let p2_rev =
        repo.changelog()?
            .rev_from_node(parents.p2.into())
            .map_err(|_| {
                HgError::corrupted(format!(
                    "dirstate points to non-existent parent node"
                ))
            })?;
    if p2_rev != NULL_REVISION {
        revs.push(p2_rev)
    }
    let mut matchers = vec![];

    for rev in revs.iter() {
        let config = patterns_for_rev(repo, *rev);
        if let Ok(Some(config)) = config {
            warnings.extend(config.warnings);
            let mut m: Box<dyn Matcher + Sync> = Box::new(AlwaysMatcher);
            if !config.includes.is_empty() {
                let (patterns, subwarnings) = parse_pattern_file_contents(
                    &config.includes,
                    Path::new(""),
                    Some(b"relglob:".as_ref()),
                    false,
                )?;
                warnings.extend(subwarnings.into_iter().map(From::from));
                m = Box::new(IncludeMatcher::new(patterns)?);
            }
            if !config.excludes.is_empty() {
                let (patterns, subwarnings) = parse_pattern_file_contents(
                    &config.excludes,
                    Path::new(""),
                    Some(b"relglob:".as_ref()),
                    false,
                )?;
                warnings.extend(subwarnings.into_iter().map(From::from));
                m = Box::new(DifferenceMatcher::new(
                    m,
                    Box::new(IncludeMatcher::new(patterns)?),
                ));
            }
            matchers.push(m);
        }
    }
    let result: Box<dyn Matcher + Sync> = match matchers.len() {
        0 => Box::new(AlwaysMatcher),
        1 => matchers.pop().expect("1 is equal to 0"),
        _ => Box::new(UnionMatcher::new(matchers)),
    };

    let matcher =
        force_include_matcher(result, &read_temporary_includes(repo)?)?;
    Ok((matcher, warnings))
}

/// Returns a matcher that returns true for any of the forced includes before
/// testing against the actual matcher
fn force_include_matcher(
    result: Box<dyn Matcher + Sync>,
    temp_includes: &[Vec<u8>],
) -> Result<Box<dyn Matcher + Sync>, PatternError> {
    if temp_includes.is_empty() {
        return Ok(result);
    }
    let forced_include_matcher = IncludeMatcher::new(
        temp_includes
            .into_iter()
            .map(|include| {
                IgnorePattern::new(PatternSyntax::Path, include, Path::new(""))
            })
            .collect(),
    )?;
    Ok(Box::new(UnionMatcher::new(vec![
        Box::new(forced_include_matcher),
        result,
    ])))
}