//! ref: composer/src/Composer/DependencyResolver/PoolOptimizer.php

use anyhow::Result;
use indexmap::IndexMap;
use shirabe_php_shim::{LogicException, PhpMixed, implode, ksort};
use shirabe_semver::compiling_matcher::CompilingMatcher;
use shirabe_semver::constraint::AnyConstraint;
use shirabe_semver::constraint::MultiConstraint;
use shirabe_semver::constraint::SimpleConstraint;
use shirabe_semver::intervals::Intervals;

use crate::dependency_resolver::PolicyInterface;
use crate::dependency_resolver::Pool;
use crate::dependency_resolver::Request;
use crate::package::BasePackageHandle;
use crate::package::PackageInterface;
use crate::package::version::VersionParser;

/// Optimizes a given pool
#[derive(Debug)]
pub struct PoolOptimizer {
    /// @var PolicyInterface
    policy: Box<dyn PolicyInterface>,

    /// @var array<int, true>
    irremovable_packages: IndexMap<i64, bool>,

    /// @var array<string, array<string, ConstraintInterface>>
    require_constraints_per_package: IndexMap<String, IndexMap<String, AnyConstraint>>,

    /// @var array<string, array<string, ConstraintInterface>>
    conflict_constraints_per_package: IndexMap<String, IndexMap<String, AnyConstraint>>,

    /// @var array<int, true>
    packages_to_remove: IndexMap<i64, bool>,

    /// @var array<int, BasePackage[]>
    aliases_per_package: IndexMap<i64, Vec<BasePackageHandle>>,

    /// @var array<string, array<string, string>>
    removed_versions_by_package: IndexMap<String, IndexMap<String, String>>,
}

#[derive(Debug, Clone)]
struct IdenticalDefinitionPointers {
    group_hash: String,
    dependency_hash: String,
}

impl PoolOptimizer {
    pub fn new(policy: Box<dyn PolicyInterface>) -> Self {
        Self {
            policy,
            irremovable_packages: IndexMap::new(),
            require_constraints_per_package: IndexMap::new(),
            conflict_constraints_per_package: IndexMap::new(),
            packages_to_remove: IndexMap::new(),
            aliases_per_package: IndexMap::new(),
            removed_versions_by_package: IndexMap::new(),
        }
    }

    pub fn optimize(&mut self, request: &Request, pool: &Pool) -> Result<Pool> {
        self.prepare(request, pool);

        self.optimize_by_identical_dependencies(request, pool)?;

        self.optimize_impossible_packages_away(request, pool);

        let optimized_pool = self.apply_removals_to_pool(pool);

        // No need to run this recursively at the moment
        // because the current optimizations cannot provide
        // even more gains when ran again. Might change
        // in the future with additional optimizations.

        self.irremovable_packages = IndexMap::new();
        self.require_constraints_per_package = IndexMap::new();
        self.conflict_constraints_per_package = IndexMap::new();
        self.packages_to_remove = IndexMap::new();
        self.aliases_per_package = IndexMap::new();
        self.removed_versions_by_package = IndexMap::new();

        Ok(optimized_pool)
    }

    fn prepare(&mut self, request: &Request, pool: &Pool) {
        let mut irremovable_package_constraint_groups: IndexMap<String, Vec<AnyConstraint>> =
            IndexMap::new();

        // Mark fixed or locked packages as irremovable
        for (_, package) in request.get_fixed_or_locked_packages() {
            irremovable_package_constraint_groups
                .entry(package.get_name())
                .or_insert_with(Vec::new)
                .push(
                    SimpleConstraint::new(
                        "==".to_string(),
                        package.get_version().to_string(),
                        None,
                    )
                    .into(),
                );
        }

        // Extract requested package requirements
        for (require, constraint) in request.get_requires() {
            self.extract_require_constraints_per_package(require, constraint.clone());
        }

        // First pass over all packages to extract information and mark package constraints irremovable
        for package in pool.get_packages() {
            // Extract package requirements
            for link in package.get_requires().values() {
                self.extract_require_constraints_per_package(
                    link.get_target(),
                    link.get_constraint().clone(),
                );
            }
            // Extract package conflicts
            for link in package.get_conflicts().values() {
                self.extract_conflict_constraints_per_package(
                    link.get_target(),
                    link.get_constraint().clone(),
                );
            }

            // Keep track of alias packages for every package so if either the alias or aliased is kept
            // we keep the others as they are a unit of packages really
            if let Some(alias_pkg) = package.as_alias() {
                self.aliases_per_package
                    .entry(alias_pkg.get_alias_of().id())
                    .or_insert_with(Vec::new)
                    .push(package.clone());
            }
        }

        let mut irremovable_package_constraints: IndexMap<String, AnyConstraint> = IndexMap::new();
        for (package_name, constraints) in irremovable_package_constraint_groups {
            irremovable_package_constraints.insert(
                package_name,
                if 1 == constraints.len() {
                    constraints.into_iter().next().unwrap()
                } else {
                    MultiConstraint::new(constraints, false, None).into()
                },
            );
        }
        // PHP: unset($irremovablePackageConstraintGroups);

        // Mark the packages as irremovable based on the constraints
        for package in pool.get_packages() {
            if !irremovable_package_constraints.contains_key(&package.get_name()) {
                continue;
            }

            let constraint = irremovable_package_constraints
                .get(&package.get_name())
                .unwrap();
            if CompilingMatcher::r#match(
                constraint,
                SimpleConstraint::OP_EQ,
                package.get_version().to_string(),
            ) {
                self.mark_package_irremovable(package);
            }
        }
    }

    fn mark_package_irremovable(&mut self, package: &BasePackageHandle) {
        self.irremovable_packages.insert(package.id(), true);
        if let Some(alias_pkg) = package.as_alias() {
            // recursing here so aliasesPerPackage for the aliasOf can be checked
            // and all its aliases marked as irremovable as well
            let aliased: BasePackageHandle = alias_pkg.get_alias_of().into();
            self.mark_package_irremovable(&aliased);
        }
        // PHP: foreach ($this->aliasesPerPackage[$package->id] as $aliasPackage)
        let alias_ids: Vec<i64> = self
            .aliases_per_package
            .get(&package.id())
            .map(|aliases| aliases.iter().map(|a| a.id()).collect())
            .unwrap_or_default();
        for alias_id in alias_ids {
            self.irremovable_packages.insert(alias_id, true);
        }
    }

    /// @return Pool Optimized pool
    fn apply_removals_to_pool(&self, pool: &Pool) -> Pool {
        let mut packages: Vec<BasePackageHandle> = vec![];
        let mut removed_versions: IndexMap<String, IndexMap<String, String>> = IndexMap::new();
        for package in pool.get_packages() {
            if !self.packages_to_remove.contains_key(&package.id()) {
                packages.push(package.clone());
            } else {
                removed_versions
                    .entry(package.get_name())
                    .or_insert_with(IndexMap::new)
                    .insert(
                        package.get_version().to_string(),
                        package.get_pretty_version().to_string(),
                    );
            }
        }

        Pool::new(
            packages,
            pool.get_unacceptable_fixed_or_locked_packages().clone(),
            removed_versions,
            self.removed_versions_by_package.clone(),
            // TODO(phase-b): PartialSecurityAdvisory is a PHP class (no Clone). Need shared ownership rework.
            todo!("pool.get_all_security_removed_package_versions().clone()"),
            pool.get_all_abandoned_removed_package_versions().clone(),
        )
    }

    fn optimize_by_identical_dependencies(
        &mut self,
        _request: &Request,
        pool: &Pool,
    ) -> Result<()> {
        let mut identical_definitions_per_package: IndexMap<
            String,
            IndexMap<String, IndexMap<String, Vec<BasePackageHandle>>>,
        > = IndexMap::new();
        let mut package_identical_definition_lookup: IndexMap<
            i64,
            IndexMap<String, IdenticalDefinitionPointers>,
        > = IndexMap::new();

        for package in pool.get_packages() {
            // If that package was already marked irremovable, we can skip
            // the entire process for it
            if self.irremovable_packages.contains_key(&package.id()) {
                continue;
            }

            self.mark_package_for_removal(package.id())?;

            let dependency_hash = self.calculate_dependency_hash(package);

            for package_name in package.get_names(false) {
                if !self
                    .require_constraints_per_package
                    .contains_key(&package_name)
                {
                    continue;
                }

                let require_constraints = self.require_constraints_per_package.get(&package_name);
                let empty_constraints = IndexMap::new();
                let require_constraints = require_constraints.unwrap_or(&empty_constraints);
                for (_, require_constraint) in require_constraints.iter() {
                    let mut group_hash_parts: Vec<String> = vec![];

                    if CompilingMatcher::r#match(
                        require_constraint,
                        SimpleConstraint::OP_EQ,
                        package.get_version().to_string(),
                    ) {
                        group_hash_parts.push(format!(
                            "require:{}",
                            require_constraint.get_pretty_string()
                        ));
                    }

                    if package.get_replaces().len() > 0 {
                        for (_, link) in package.get_replaces() {
                            if CompilingMatcher::r#match(
                                link.get_constraint(),
                                SimpleConstraint::OP_EQ,
                                package.get_version().to_string(),
                            ) {
                                // Use the same hash part as the regular require hash because that's what the replacement does
                                group_hash_parts.push(format!(
                                    "require:{}",
                                    link.get_constraint().get_pretty_string()
                                ));
                            }
                        }
                    }

                    if let Some(conflict_constraints) =
                        self.conflict_constraints_per_package.get(&package_name)
                    {
                        for (_, conflict_constraint) in conflict_constraints {
                            if CompilingMatcher::r#match(
                                conflict_constraint,
                                SimpleConstraint::OP_EQ,
                                package.get_version().to_string(),
                            ) {
                                group_hash_parts.push(format!(
                                    "conflict:{}",
                                    conflict_constraint.get_pretty_string()
                                ));
                            }
                        }
                    }

                    if 0 == group_hash_parts.len() {
                        continue;
                    }

                    let group_hash = implode("", &group_hash_parts);
                    identical_definitions_per_package
                        .entry(package_name.clone())
                        .or_insert_with(IndexMap::new)
                        .entry(group_hash.clone())
                        .or_insert_with(IndexMap::new)
                        .entry(dependency_hash.clone())
                        .or_insert_with(Vec::new)
                        .push(package.clone());
                    package_identical_definition_lookup
                        .entry(package.id())
                        .or_insert_with(IndexMap::new)
                        .insert(
                            package_name.clone(),
                            IdenticalDefinitionPointers {
                                group_hash,
                                dependency_hash: dependency_hash.clone(),
                            },
                        );
                }
            }
        }

        // PHP: foreach ($identicalDefinitionsPerPackage as $constraintGroups)
        let identical_clone = identical_definitions_per_package.clone();
        for (_, constraint_groups) in identical_clone.iter() {
            for (_, constraint_group) in constraint_groups.iter() {
                for (_, packages) in constraint_group.iter() {
                    // Only one package in this constraint group has the same requirements, we're not allowed to remove that package
                    if 1 == packages.len() {
                        self.keep_package(
                            &packages[0],
                            &identical_definitions_per_package,
                            &package_identical_definition_lookup,
                        );
                        continue;
                    }

                    // Otherwise we find out which one is the preferred package in this constraint group which is
                    // then not allowed to be removed either
                    let mut literals: Vec<i64> = vec![];

                    for package in packages {
                        literals.push(package.id());
                    }

                    for preferred_literal in
                        self.policy
                            .select_preferred_packages(pool, literals.clone(), None)
                    {
                        self.keep_package(
                            &pool.literal_to_package(preferred_literal),
                            &identical_definitions_per_package,
                            &package_identical_definition_lookup,
                        );
                    }
                }
            }
        }

        Ok(())
    }

    fn calculate_dependency_hash(&self, package: &BasePackageHandle) -> String {
        let mut hash = String::new();

        let hash_relevant_links: Vec<(&str, Vec<crate::package::Link>)> = vec![
            (
                "requires",
                package.get_requires().values().cloned().collect(),
            ),
            (
                "conflicts",
                package.get_conflicts().values().cloned().collect(),
            ),
            (
                "replaces",
                package.get_replaces().values().cloned().collect(),
            ),
            (
                "provides",
                package.get_provides().values().cloned().collect(),
            ),
        ];

        for (key, links) in hash_relevant_links {
            if 0 == links.len() {
                continue;
            }

            // start new hash section
            hash.push_str(&format!("{}:", key));

            let mut subhash: IndexMap<String, String> = IndexMap::new();

            for link in links {
                // To get the best dependency hash matches we should use Intervals::compactConstraint() here.
                // However, the majority of projects are going to specify their constraints already pretty
                // much in the best variant possible. In other words, we'd be wasting time here and it would actually hurt
                // performance more than the additional few packages that could be filtered out would benefit the process.
                subhash.insert(
                    link.get_target().to_string(),
                    link.get_constraint().to_string(),
                );
            }

            // Sort for best result
            ksort(&mut subhash);

            for (target, constraint) in subhash {
                hash.push_str(&format!("{}@{}", target, constraint));
            }
        }

        hash
    }

    fn mark_package_for_removal(&mut self, id: i64) -> Result<()> {
        // We are not allowed to remove packages if they have been marked as irremovable
        if self.irremovable_packages.contains_key(&id) {
            return Err(LogicException {
                message: "Attempted removing a package which was previously marked irremovable"
                    .to_string(),
                code: 0,
            }
            .into());
        }

        self.packages_to_remove.insert(id, true);
        Ok(())
    }

    /// @param array<string, array<string, array<string, list<BasePackage>>>> $identicalDefinitionsPerPackage
    /// @param array<int, array<string, array{groupHash: string, dependencyHash: string}>> $packageIdenticalDefinitionLookup
    fn keep_package(
        &mut self,
        package: &BasePackageHandle,
        identical_definitions_per_package: &IndexMap<
            String,
            IndexMap<String, IndexMap<String, Vec<BasePackageHandle>>>,
        >,
        package_identical_definition_lookup: &IndexMap<
            i64,
            IndexMap<String, IdenticalDefinitionPointers>,
        >,
    ) {
        // Already marked to keep
        if !self.packages_to_remove.contains_key(&package.id()) {
            return;
        }

        self.packages_to_remove.shift_remove(&package.id());

        if let Some(alias_pkg) = package.as_alias() {
            // recursing here so aliasesPerPackage for the aliasOf can be checked
            // and all its aliases marked to be kept as well
            let aliased: BasePackageHandle = alias_pkg.get_alias_of().into();
            self.keep_package(
                &aliased,
                identical_definitions_per_package,
                package_identical_definition_lookup,
            );
        }

        // record all the versions of the package group so we can list them later in Problem output
        for name in package.get_names(false) {
            if let Some(per_name) = package_identical_definition_lookup.get(&package.id()) {
                if let Some(package_group_pointers) = per_name.get(&name) {
                    let package_group = identical_definitions_per_package
                        .get(&name)
                        .and_then(|m| m.get(&package_group_pointers.group_hash))
                        .and_then(|m| m.get(&package_group_pointers.dependency_hash));
                    if let Some(package_group) = package_group {
                        for pkg in package_group {
                            let pkg: BasePackageHandle = if let Some(alias_pkg) = pkg.as_alias() {
                                if alias_pkg.get_pretty_version()
                                    == VersionParser::DEFAULT_BRANCH_ALIAS
                                {
                                    alias_pkg.get_alias_of().into()
                                } else {
                                    pkg.clone()
                                }
                            } else {
                                pkg.clone()
                            };
                            self.removed_versions_by_package
                                .entry(package.ptr_id().to_string())
                                .or_insert_with(IndexMap::new)
                                .insert(
                                    pkg.get_version().to_string(),
                                    pkg.get_pretty_version().to_string(),
                                );
                        }
                    }
                }
            }
        }

        let alias_info: Vec<(i64, Vec<String>)> = self
            .aliases_per_package
            .get(&package.id())
            .map(|aliases| {
                aliases
                    .iter()
                    .map(|a| (a.id(), a.get_names(false)))
                    .collect()
            })
            .unwrap_or_default();
        for (alias_id, alias_names) in alias_info {
            self.packages_to_remove.shift_remove(&alias_id);

            // record all the versions of the package group so we can list them later in Problem output
            for name in alias_names {
                if let Some(per_name) = package_identical_definition_lookup.get(&alias_id) {
                    if let Some(package_group_pointers) = per_name.get(&name) {
                        let package_group = identical_definitions_per_package
                            .get(&name)
                            .and_then(|m| m.get(&package_group_pointers.group_hash))
                            .and_then(|m| m.get(&package_group_pointers.dependency_hash));
                        if let Some(package_group) = package_group {
                            for pkg in package_group {
                                let pkg: BasePackageHandle = if let Some(alias_pkg) = pkg.as_alias()
                                {
                                    if alias_pkg.get_pretty_version()
                                        == VersionParser::DEFAULT_BRANCH_ALIAS
                                    {
                                        alias_pkg.get_alias_of().into()
                                    } else {
                                        pkg.clone()
                                    }
                                } else {
                                    pkg.clone()
                                };
                                self.removed_versions_by_package
                                    .entry(format!("alias-{}", alias_id))
                                    .or_insert_with(IndexMap::new)
                                    .insert(
                                        pkg.get_version().to_string(),
                                        pkg.get_pretty_version().to_string(),
                                    );
                            }
                        }
                    }
                }
            }
        }
    }

    /// Use the list of locked packages to constrain the loaded packages
    /// This will reduce packages with significant numbers of historical versions to a smaller number
    /// and reduce the resulting rule set that is generated
    fn optimize_impossible_packages_away(&mut self, request: &Request, pool: &Pool) {
        if request.get_locked_packages().len() == 0 {
            return;
        }

        let mut package_index: IndexMap<String, IndexMap<i64, BasePackageHandle>> = IndexMap::new();

        for package in pool.get_packages() {
            let id = package.id();

            // Do not remove irremovable packages
            if self.irremovable_packages.contains_key(&id) {
                continue;
            }
            // Do not remove a package aliased by another package, nor aliases
            if self.aliases_per_package.contains_key(&id) || package.as_alias().is_some() {
                continue;
            }
            // Do not remove locked packages
            if request.is_fixed_package(&package) || request.is_locked_package(&package) {
                continue;
            }

            package_index
                .entry(package.get_name())
                .or_insert_with(IndexMap::new)
                .insert(package.id(), package.clone());
        }

        for (_, package) in request.get_locked_packages() {
            // If this locked package is no longer required by root or anything in the pool, it may get uninstalled so do not apply its requirements
            // In a case where a requirement WERE to appear in the pool by a package that would not be used, it would've been unlocked and so not filtered still
            let mut is_unused_package = true;
            for package_name in package.get_names(false) {
                if self
                    .require_constraints_per_package
                    .contains_key(&package_name)
                {
                    is_unused_package = false;
                    break;
                }
            }

            if is_unused_package {
                continue;
            }

            for link in package.get_requires().values() {
                let require = link.get_target();
                if !package_index.contains_key(require) {
                    continue;
                }

                let link_constraint = link.get_constraint();
                let ids: Vec<i64> = package_index
                    .get(require)
                    .map(|m| m.keys().copied().collect())
                    .unwrap_or_default();
                for id in ids {
                    let version_str = package_index
                        .get(require)
                        .and_then(|m| m.get(&id))
                        .map(|p| p.get_version().to_string());
                    if let Some(version_str) = version_str {
                        if false
                            == CompilingMatcher::r#match(
                                link_constraint,
                                SimpleConstraint::OP_EQ,
                                version_str,
                            )
                        {
                            // TODO(phase-b): mark_package_for_removal returns Result; ignoring here
                            let _ = self.mark_package_for_removal(id);
                            if let Some(map) = package_index.get_mut(require) {
                                map.shift_remove(&id);
                            }
                        }
                    }
                }
            }
        }
    }

    /// Disjunctive require constraints need to be considered in their own group. E.g. "^2.14 || ^3.3" needs to generate
    /// two require constraint groups in order for us to keep the best matching package for "^2.14" AND "^3.3" as otherwise, we'd
    /// only keep either one which can cause trouble (e.g. when using --prefer-lowest).
    ///
    /// @return void
    fn extract_require_constraints_per_package(
        &mut self,
        package: &str,
        constraint: AnyConstraint,
    ) {
        for expanded in self.expand_disjunctive_multi_constraints(constraint) {
            self.require_constraints_per_package
                .entry(package.to_string())
                .or_insert_with(IndexMap::new)
                .insert(expanded.to_string(), expanded);
        }
    }

    /// Disjunctive conflict constraints need to be considered in their own group. E.g. "^2.14 || ^3.3" needs to generate
    /// two conflict constraint groups in order for us to keep the best matching package for "^2.14" AND "^3.3" as otherwise, we'd
    /// only keep either one which can cause trouble (e.g. when using --prefer-lowest).
    ///
    /// @return void
    fn extract_conflict_constraints_per_package(
        &mut self,
        package: &str,
        constraint: AnyConstraint,
    ) {
        for expanded in self.expand_disjunctive_multi_constraints(constraint) {
            self.conflict_constraints_per_package
                .entry(package.to_string())
                .or_insert_with(IndexMap::new)
                .insert(expanded.to_string(), expanded);
        }
    }

    /// @return ConstraintInterface[]
    fn expand_disjunctive_multi_constraints(
        &self,
        constraint: AnyConstraint,
    ) -> Vec<AnyConstraint> {
        let constraint = Intervals::compact_constraint(&constraint).unwrap_or(constraint);

        if let Some(multi) = constraint.as_multi_constraint() {
            if multi.is_disjunctive_mc() {
                // No need to call ourselves recursively here because Intervals::compactConstraint() ensures that there
                // are no nested disjunctive MultiConstraint instances possible
                return multi.get_constraints().iter().map(|c| c.clone()).collect();
            }
        }

        // Regular constraints and conjunctive MultiConstraints
        vec![constraint]
    }
}