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,

    ])))

}