use std::ops::{Deref, DerefMut};
use std::path::{Path, PathBuf};
use std::str;

use anyhow::Context as _;

use super::dependency::Dependency;
use crate::core::dependency::DepKind;
use crate::core::FeatureValue;
use crate::util::interning::InternedString;
use crate::CargoResult;

/// Dependency table to add dep to
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct DepTable {
    kind: DepKind,
    target: Option<String>,
}

impl DepTable {
    const KINDS: &'static [Self] = &[
        Self::new().set_kind(DepKind::Normal),
        Self::new().set_kind(DepKind::Development),
        Self::new().set_kind(DepKind::Build),
    ];

    /// Reference to a Dependency Table
    pub const fn new() -> Self {
        Self {
            kind: DepKind::Normal,
            target: None,
        }
    }

    /// Choose the type of dependency
    pub const fn set_kind(mut self, kind: DepKind) -> Self {
        self.kind = kind;
        self
    }

    /// Choose the platform for the dependency
    pub fn set_target(mut self, target: impl Into<String>) -> Self {
        self.target = Some(target.into());
        self
    }

    /// Type of dependency
    pub fn kind(&self) -> DepKind {
        self.kind
    }

    /// Platform for the dependency
    pub fn target(&self) -> Option<&str> {
        self.target.as_deref()
    }

    /// Keys to the table
    pub fn to_table(&self) -> Vec<&str> {
        if let Some(target) = &self.target {
            vec!["target", target, self.kind_table()]
        } else {
            vec![self.kind_table()]
        }
    }

    fn kind_table(&self) -> &str {
        match self.kind {
            DepKind::Normal => "dependencies",
            DepKind::Development => "dev-dependencies",
            DepKind::Build => "build-dependencies",
        }
    }
}

impl Default for DepTable {
    fn default() -> Self {
        Self::new()
    }
}

impl From<DepKind> for DepTable {
    fn from(other: DepKind) -> Self {
        Self::new().set_kind(other)
    }
}

/// A Cargo manifest
#[derive(Debug, Clone)]
pub struct Manifest {
    /// Manifest contents as TOML data
    pub data: toml_edit::Document,
}

impl Manifest {
    /// Get the manifest's package name
    pub fn package_name(&self) -> CargoResult<&str> {
        self.data
            .as_table()
            .get("package")
            .and_then(|m| m.get("name"))
            .and_then(|m| m.as_str())
            .ok_or_else(parse_manifest_err)
    }

    /// Get the specified table from the manifest.
    pub fn get_table<'a>(&'a self, table_path: &[String]) -> CargoResult<&'a toml_edit::Item> {
        /// Descend into a manifest until the required table is found.
        fn descend<'a>(
            input: &'a toml_edit::Item,
            path: &[String],
        ) -> CargoResult<&'a toml_edit::Item> {
            if let Some(segment) = path.get(0) {
                let value = input
                    .get(&segment)
                    .ok_or_else(|| non_existent_table_err(segment))?;

                if value.is_table_like() {
                    descend(value, &path[1..])
                } else {
                    Err(non_existent_table_err(segment))
                }
            } else {
                Ok(input)
            }
        }

        descend(self.data.as_item(), table_path)
    }

    /// Get the specified table from the manifest.
    pub fn get_table_mut<'a>(
        &'a mut self,
        table_path: &[String],
    ) -> CargoResult<&'a mut toml_edit::Item> {
        /// Descend into a manifest until the required table is found.
        fn descend<'a>(
            input: &'a mut toml_edit::Item,
            path: &[String],
        ) -> CargoResult<&'a mut toml_edit::Item> {
            if let Some(segment) = path.get(0) {
                let mut default_table = toml_edit::Table::new();
                default_table.set_implicit(true);
                let value = input[&segment].or_insert(toml_edit::Item::Table(default_table));

                if value.is_table_like() {
                    descend(value, &path[1..])
                } else {
                    Err(non_existent_table_err(segment))
                }
            } else {
                Ok(input)
            }
        }

        descend(self.data.as_item_mut(), table_path)
    }

    /// Get all sections in the manifest that exist and might contain dependencies.
    /// The returned items are always `Table` or `InlineTable`.
    pub fn get_sections(&self) -> Vec<(DepTable, toml_edit::Item)> {
        let mut sections = Vec::new();

        for table in DepTable::KINDS {
            let dependency_type = table.kind_table();
            // Dependencies can be in the three standard sections...
            if self
                .data
                .get(dependency_type)
                .map(|t| t.is_table_like())
                .unwrap_or(false)
            {
                sections.push((table.clone(), self.data[dependency_type].clone()))
            }

            // ... and in `target.<target>.(build-/dev-)dependencies`.
            let target_sections = self
                .data
                .as_table()
                .get("target")
                .and_then(toml_edit::Item::as_table_like)
                .into_iter()
                .flat_map(toml_edit::TableLike::iter)
                .filter_map(|(target_name, target_table)| {
                    let dependency_table = target_table.get(dependency_type)?;
                    dependency_table.as_table_like().map(|_| {
                        (
                            table.clone().set_target(target_name),
                            dependency_table.clone(),
                        )
                    })
                });

            sections.extend(target_sections);
        }

        sections
    }

    pub fn get_legacy_sections(&self) -> Vec<String> {
        let mut result = Vec::new();

        for dependency_type in ["dev_dependencies", "build_dependencies"] {
            if self.data.contains_key(dependency_type) {
                result.push(dependency_type.to_owned());
            }

            // ... and in `target.<target>.(build-/dev-)dependencies`.
            result.extend(
                self.data
                    .as_table()
                    .get("target")
                    .and_then(toml_edit::Item::as_table_like)
                    .into_iter()
                    .flat_map(toml_edit::TableLike::iter)
                    .filter_map(|(target_name, target_table)| {
                        if target_table.as_table_like()?.contains_key(dependency_type) {
                            Some(format!("target.{target_name}.{dependency_type}"))
                        } else {
                            None
                        }
                    }),
            );
        }
        result
    }
}

impl str::FromStr for Manifest {
    type Err = anyhow::Error;

    /// Read manifest data from string
    fn from_str(input: &str) -> ::std::result::Result<Self, Self::Err> {
        let d: toml_edit::Document = input.parse().context("Manifest not valid TOML")?;

        Ok(Manifest { data: d })
    }
}

impl std::fmt::Display for Manifest {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let s = self.data.to_string();
        s.fmt(f)
    }
}

/// A Cargo manifest that is available locally.
#[derive(Debug)]
pub struct LocalManifest {
    /// Path to the manifest
    pub path: PathBuf,
    /// Manifest contents
    pub manifest: Manifest,
}

impl Deref for LocalManifest {
    type Target = Manifest;

    fn deref(&self) -> &Manifest {
        &self.manifest
    }
}

impl DerefMut for LocalManifest {
    fn deref_mut(&mut self) -> &mut Manifest {
        &mut self.manifest
    }
}

impl LocalManifest {
    /// Construct the `LocalManifest` corresponding to the `Path` provided.
    pub fn try_new(path: &Path) -> CargoResult<Self> {
        if !path.is_absolute() {
            anyhow::bail!("can only edit absolute paths, got {}", path.display());
        }
        let data = cargo_util::paths::read(&path)?;
        let manifest = data.parse().context("Unable to parse Cargo.toml")?;
        Ok(LocalManifest {
            manifest,
            path: path.to_owned(),
        })
    }

    /// Write changes back to the file
    pub fn write(&self) -> CargoResult<()> {
        if !self.manifest.data.contains_key("package")
            && !self.manifest.data.contains_key("project")
        {
            if self.manifest.data.contains_key("workspace") {
                anyhow::bail!(
                    "found virtual manifest at {}, but this command requires running against an \
                         actual package in this workspace.",
                    self.path.display()
                );
            } else {
                anyhow::bail!(
                    "missing expected `package` or `project` fields in {}",
                    self.path.display()
                );
            }
        }

        let s = self.manifest.data.to_string();
        let new_contents_bytes = s.as_bytes();

        cargo_util::paths::write(&self.path, new_contents_bytes)
    }

    /// Lookup a dependency
    pub fn get_dependency_versions<'s>(
        &'s self,
        dep_key: &'s str,
    ) -> impl Iterator<Item = (DepTable, CargoResult<Dependency>)> + 's {
        let crate_root = self.path.parent().expect("manifest path is absolute");
        self.get_sections()
            .into_iter()
            .filter_map(move |(table_path, table)| {
                let table = table.into_table().ok()?;
                Some(
                    table
                        .into_iter()
                        .filter_map(|(key, item)| {
                            if key.as_str() == dep_key {
                                Some((table_path.clone(), key, item))
                            } else {
                                None
                            }
                        })
                        .collect::<Vec<_>>(),
                )
            })
            .flatten()
            .map(move |(table_path, dep_key, dep_item)| {
                let dep = Dependency::from_toml(crate_root, &dep_key, &dep_item);
                (table_path, dep)
            })
    }

    /// Add entry to a Cargo.toml.
    pub fn insert_into_table(
        &mut self,
        table_path: &[String],
        dep: &Dependency,
    ) -> CargoResult<()> {
        let crate_root = self
            .path
            .parent()
            .expect("manifest path is absolute")
            .to_owned();
        let dep_key = dep.toml_key();

        let table = self.get_table_mut(table_path)?;
        if let Some((mut dep_key, dep_item)) = table
            .as_table_like_mut()
            .unwrap()
            .get_key_value_mut(dep_key)
        {
            dep.update_toml(&crate_root, &mut dep_key, dep_item);
        } else {
            let new_dependency = dep.to_toml(&crate_root);
            table[dep_key] = new_dependency;
        }
        if let Some(t) = table.as_inline_table_mut() {
            t.fmt()
        }

        Ok(())
    }

    /// Remove references to `dep_key` if its no longer present
    pub fn gc_dep(&mut self, dep_key: &str) {
        let explicit_dep_activation = self.is_explicit_dep_activation(dep_key);
        let status = self.dep_status(dep_key);

        if let Some(toml_edit::Item::Table(feature_table)) =
            self.data.as_table_mut().get_mut("features")
        {
            for (_feature, mut feature_values) in feature_table.iter_mut() {
                if let toml_edit::Item::Value(toml_edit::Value::Array(feature_values)) =
                    &mut feature_values
                {
                    fix_feature_activations(
                        feature_values,
                        dep_key,
                        status,
                        explicit_dep_activation,
                    );
                }
            }
        }
    }

    fn is_explicit_dep_activation(&self, dep_key: &str) -> bool {
        if let Some(toml_edit::Item::Table(feature_table)) = self.data.as_table().get("features") {
            for values in feature_table
                .iter()
                .map(|(_, a)| a)
                .filter_map(|i| i.as_value())
                .filter_map(|v| v.as_array())
            {
                for value in values.iter().filter_map(|v| v.as_str()) {
                    let value = FeatureValue::new(InternedString::new(value));
                    if let FeatureValue::Dep { dep_name } = &value {
                        if dep_name.as_str() == dep_key {
                            return true;
                        }
                    }
                }
            }
        }

        false
    }

    fn dep_status(&self, dep_key: &str) -> DependencyStatus {
        let mut status = DependencyStatus::None;
        for (_, tbl) in self.get_sections() {
            if let toml_edit::Item::Table(tbl) = tbl {
                if let Some(dep_item) = tbl.get(dep_key) {
                    let optional = dep_item
                        .get("optional")
                        .and_then(|i| i.as_value())
                        .and_then(|i| i.as_bool())
                        .unwrap_or(false);
                    if optional {
                        return DependencyStatus::Optional;
                    } else {
                        status = DependencyStatus::Required;
                    }
                }
            }
        }
        status
    }
}

#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
enum DependencyStatus {
    None,
    Optional,
    Required,
}

fn fix_feature_activations(
    feature_values: &mut toml_edit::Array,
    dep_key: &str,
    status: DependencyStatus,
    explicit_dep_activation: bool,
) {
    let remove_list: Vec<usize> = feature_values
        .iter()
        .enumerate()
        .filter_map(|(idx, value)| value.as_str().map(|s| (idx, s)))
        .filter_map(|(idx, value)| {
            let parsed_value = FeatureValue::new(InternedString::new(value));
            match status {
                DependencyStatus::None => match (parsed_value, explicit_dep_activation) {
                    (FeatureValue::Feature(dep_name), false)
                    | (FeatureValue::Dep { dep_name }, _)
                    | (FeatureValue::DepFeature { dep_name, .. }, _) => dep_name == dep_key,
                    _ => false,
                },
                DependencyStatus::Optional => false,
                DependencyStatus::Required => match (parsed_value, explicit_dep_activation) {
                    (FeatureValue::Feature(dep_name), false)
                    | (FeatureValue::Dep { dep_name }, _) => dep_name == dep_key,
                    (FeatureValue::Feature(_), true) | (FeatureValue::DepFeature { .. }, _) => {
                        false
                    }
                },
            }
            .then(|| idx)
        })
        .collect();

    // Remove found idx in revers order so we don't invalidate the idx.
    for idx in remove_list.iter().rev() {
        feature_values.remove(*idx);
    }

    if status == DependencyStatus::Required {
        for value in feature_values.iter_mut() {
            let parsed_value = if let Some(value) = value.as_str() {
                FeatureValue::new(InternedString::new(value))
            } else {
                continue;
            };
            if let FeatureValue::DepFeature {
                dep_name,
                dep_feature,
                weak,
            } = parsed_value
            {
                if dep_name == dep_key && weak {
                    *value = format!("{dep_name}/{dep_feature}").into();
                }
            }
        }
    }
}

pub fn str_or_1_len_table(item: &toml_edit::Item) -> bool {
    item.is_str() || item.as_table_like().map(|t| t.len() == 1).unwrap_or(false)
}

fn parse_manifest_err() -> anyhow::Error {
    anyhow::format_err!("unable to parse external Cargo.toml")
}

fn non_existent_table_err(table: impl std::fmt::Display) -> anyhow::Error {
    anyhow::format_err!("the table `{table}` could not be found.")
}