//! Fundamental domain types.

use serde::{Deserialize, Deserializer, Serialize};
use std::{
    num::NonZeroU64,
    path::{Path, PathBuf},
};
use thiserror::Error;

/// A value that failed a domain-level invariant.
#[derive(Debug, Clone, PartialEq, Eq, Error)]
#[error("domain invariant violated: {detail}")]
pub struct InvariantViolation {
    detail: &'static str,
}

impl InvariantViolation {
    /// Creates a new invariant violation.
    #[must_use]
    pub fn new(detail: &'static str) -> Self {
        Self { detail }
    }
}

/// Process generation for a rust-analyzer worker.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
#[serde(transparent)]
pub struct Generation(NonZeroU64);

impl Generation {
    /// Returns the first generation.
    #[must_use]
    pub fn genesis() -> Self {
        Self(NonZeroU64::MIN)
    }

    /// Returns the inner integer value.
    #[must_use]
    pub fn get(self) -> u64 {
        self.0.get()
    }

    /// Advances to the next generation.
    #[must_use]
    pub fn next(self) -> Self {
        let next = self.get().saturating_add(1);
        let non_zero = NonZeroU64::new(next).map_or(NonZeroU64::MAX, |value| value);
        Self(non_zero)
    }
}

/// A non-empty absolute workspace root.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct WorkspaceRoot(PathBuf);

impl WorkspaceRoot {
    /// Constructs a validated workspace root.
    pub fn try_new(path: PathBuf) -> Result<Self, InvariantViolation> {
        if !path.is_absolute() {
            return Err(InvariantViolation::new("workspace root must be absolute"));
        }
        if path.as_os_str().is_empty() {
            return Err(InvariantViolation::new("workspace root must be non-empty"));
        }
        Ok(Self(path))
    }

    /// Returns the root path.
    #[must_use]
    pub fn as_path(&self) -> &Path {
        self.0.as_path()
    }
}

/// A non-empty absolute source file path.
#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize)]
#[serde(transparent)]
pub struct SourceFilePath(PathBuf);

impl SourceFilePath {
    /// Constructs a validated source file path.
    pub fn try_new(path: PathBuf) -> Result<Self, InvariantViolation> {
        if !path.is_absolute() {
            return Err(InvariantViolation::new("source file path must be absolute"));
        }
        if path.as_os_str().is_empty() {
            return Err(InvariantViolation::new(
                "source file path must be non-empty",
            ));
        }
        Ok(Self(path))
    }

    /// Returns the underlying path.
    #[must_use]
    pub fn as_path(&self) -> &Path {
        self.0.as_path()
    }
}

impl<'de> Deserialize<'de> for SourceFilePath {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let path = PathBuf::deserialize(deserializer)?;
        Self::try_new(path).map_err(serde::de::Error::custom)
    }
}

/// One-indexed source line number.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
#[serde(transparent)]
pub struct OneIndexedLine(NonZeroU64);

impl OneIndexedLine {
    /// Constructs a one-indexed line.
    pub fn try_new(raw: u64) -> Result<Self, InvariantViolation> {
        let line = NonZeroU64::new(raw).ok_or(InvariantViolation::new("line must be >= 1"))?;
        Ok(Self(line))
    }

    /// Returns the one-indexed value.
    #[must_use]
    pub fn get(self) -> u64 {
        self.0.get()
    }

    /// Returns the corresponding zero-indexed value for LSP.
    #[must_use]
    pub fn to_zero_indexed(self) -> u32 {
        let raw = self.get().saturating_sub(1);
        u32::try_from(raw).unwrap_or(u32::MAX)
    }
}

/// One-indexed source column number.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
#[serde(transparent)]
pub struct OneIndexedColumn(NonZeroU64);

impl OneIndexedColumn {
    /// Constructs a one-indexed column.
    pub fn try_new(raw: u64) -> Result<Self, InvariantViolation> {
        let column = NonZeroU64::new(raw).ok_or(InvariantViolation::new("column must be >= 1"))?;
        Ok(Self(column))
    }

    /// Returns the one-indexed value.
    #[must_use]
    pub fn get(self) -> u64 {
        self.0.get()
    }

    /// Returns the corresponding zero-indexed value for LSP.
    #[must_use]
    pub fn to_zero_indexed(self) -> u32 {
        let raw = self.get().saturating_sub(1);
        u32::try_from(raw).unwrap_or(u32::MAX)
    }
}

/// A file-local source point.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct SourcePoint {
    line: OneIndexedLine,
    column: OneIndexedColumn,
}

impl SourcePoint {
    /// Constructs a file-local source point.
    #[must_use]
    pub fn new(line: OneIndexedLine, column: OneIndexedColumn) -> Self {
        Self { line, column }
    }

    /// Returns the line component.
    #[must_use]
    pub fn line(self) -> OneIndexedLine {
        self.line
    }

    /// Returns the column component.
    #[must_use]
    pub fn column(self) -> OneIndexedColumn {
        self.column
    }
}

/// Request position in a source file.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct SourcePosition {
    file_path: SourceFilePath,
    #[serde(flatten)]
    point: SourcePoint,
}

impl SourcePosition {
    /// Constructs a request position.
    #[must_use]
    pub fn new(file_path: SourceFilePath, point: SourcePoint) -> Self {
        Self { file_path, point }
    }

    /// Returns the source file path.
    #[must_use]
    pub fn file_path(&self) -> &SourceFilePath {
        &self.file_path
    }

    /// Returns the file-local point.
    #[must_use]
    pub fn point(&self) -> SourcePoint {
        self.point
    }

    /// Returns the one-indexed line.
    #[must_use]
    pub fn line(&self) -> OneIndexedLine {
        self.point.line()
    }

    /// Returns the one-indexed column.
    #[must_use]
    pub fn column(&self) -> OneIndexedColumn {
        self.point.column()
    }
}

#[derive(Debug, Clone, Deserialize)]
struct SourcePositionWire {
    file_path: SourceFilePath,
    #[serde(flatten)]
    point: SourcePoint,
}

impl<'de> Deserialize<'de> for SourcePosition {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let SourcePositionWire { file_path, point } =
            SourcePositionWire::deserialize(deserializer)?;
        Ok(Self::new(file_path, point))
    }
}

/// A concrete source location.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct SourceLocation {
    file_path: SourceFilePath,
    #[serde(flatten)]
    point: SourcePoint,
}

impl SourceLocation {
    /// Constructs a source location.
    #[must_use]
    pub fn new(file_path: SourceFilePath, point: SourcePoint) -> Self {
        Self { file_path, point }
    }

    /// Returns the source file path.
    #[must_use]
    pub fn file_path(&self) -> &SourceFilePath {
        &self.file_path
    }

    /// Returns the file-local point.
    #[must_use]
    pub fn point(&self) -> SourcePoint {
        self.point
    }

    /// Returns the one-indexed line.
    #[must_use]
    pub fn line(&self) -> OneIndexedLine {
        self.point.line()
    }

    /// Returns the one-indexed column.
    #[must_use]
    pub fn column(&self) -> OneIndexedColumn {
        self.point.column()
    }
}

#[derive(Debug, Clone, Deserialize)]
struct SourceLocationWire {
    file_path: SourceFilePath,
    #[serde(flatten)]
    point: SourcePoint,
}

impl<'de> Deserialize<'de> for SourceLocation {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let SourceLocationWire { file_path, point } =
            SourceLocationWire::deserialize(deserializer)?;
        Ok(Self::new(file_path, point))
    }
}

/// A source range in a specific file.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct SourceRange {
    file_path: SourceFilePath,
    start: SourcePoint,
    end: SourcePoint,
}

impl SourceRange {
    /// Constructs a validated source range.
    pub fn try_new(
        file_path: SourceFilePath,
        start: SourcePoint,
        end: SourcePoint,
    ) -> Result<Self, InvariantViolation> {
        if end < start {
            return Err(InvariantViolation::new(
                "source range end must not precede start",
            ));
        }
        Ok(Self {
            file_path,
            start,
            end,
        })
    }

    /// Returns the source file path.
    #[must_use]
    pub fn file_path(&self) -> &SourceFilePath {
        &self.file_path
    }

    /// Returns the start point.
    #[must_use]
    pub fn start(&self) -> SourcePoint {
        self.start
    }

    /// Returns the end point.
    #[must_use]
    pub fn end(&self) -> SourcePoint {
        self.end
    }
}

#[derive(Debug, Clone, Deserialize)]
struct SourceRangeWire {
    file_path: SourceFilePath,
    start: SourcePoint,
    end: SourcePoint,
}

impl<'de> Deserialize<'de> for SourceRange {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let SourceRangeWire {
            file_path,
            start,
            end,
        } = SourceRangeWire::deserialize(deserializer)?;
        Self::try_new(file_path, start, end).map_err(serde::de::Error::custom)
    }
}

/// A monotonically increasing request sequence.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct RequestSequence(NonZeroU64);

impl RequestSequence {
    /// Starts a fresh sequence.
    #[must_use]
    pub fn genesis() -> Self {
        Self(NonZeroU64::MIN)
    }

    /// Returns the current integer value.
    #[must_use]
    pub fn get(self) -> u64 {
        self.0.get()
    }

    /// Consumes and returns the next sequence.
    #[must_use]
    pub fn next(self) -> Self {
        let next = self.get().saturating_add(1);
        let non_zero = NonZeroU64::new(next).map_or(NonZeroU64::MAX, |value| value);
        Self(non_zero)
    }
}

#[cfg(test)]
mod tests {
    use super::{
        Generation, InvariantViolation, OneIndexedColumn, OneIndexedLine, RequestSequence,
        SourceFilePath, SourcePoint, SourceRange,
    };
    use assert_matches::assert_matches;
    use std::{num::NonZeroU64, path::PathBuf};

    #[test]
    fn generation_advances_monotonically() {
        let first = Generation::genesis();
        let second = first.next();
        let third = second.next();
        assert!(first < second);
        assert!(second < third);
    }

    #[test]
    fn generation_saturates_at_maximum() {
        let max = Generation(NonZeroU64::MAX);
        assert_eq!(max.next(), max);
    }

    #[test]
    fn line_must_be_one_or_greater() {
        assert_matches!(OneIndexedLine::try_new(0), Err(InvariantViolation { .. }));
    }

    #[test]
    fn column_must_be_one_or_greater() {
        assert_matches!(OneIndexedColumn::try_new(0), Err(InvariantViolation { .. }));
    }

    #[test]
    fn source_range_rejects_reversed_points() {
        let file_path = SourceFilePath::try_new(PathBuf::from("/tmp/range.rs"));
        assert!(file_path.is_ok());
        let file_path = match file_path {
            Ok(value) => value,
            Err(_) => return,
        };
        let start = SourcePoint::new(
            OneIndexedLine::try_new(4).unwrap_or(OneIndexedLine(NonZeroU64::MIN)),
            OneIndexedColumn::try_new(3).unwrap_or(OneIndexedColumn(NonZeroU64::MIN)),
        );
        let end = SourcePoint::new(
            OneIndexedLine::try_new(2).unwrap_or(OneIndexedLine(NonZeroU64::MIN)),
            OneIndexedColumn::try_new(1).unwrap_or(OneIndexedColumn(NonZeroU64::MIN)),
        );
        assert_matches!(
            SourceRange::try_new(file_path, start, end),
            Err(InvariantViolation { .. })
        );
    }

    #[test]
    fn request_sequence_saturates_at_maximum() {
        let max = RequestSequence(NonZeroU64::MAX);
        assert_eq!(max.next().get(), u64::MAX);
    }
}