// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use codespan_reporting::diagnostic;
use codespan_reporting::files;
use serde::Serialize;
use std::fmt;
use std::ops;

/// File identifier.
/// References a source file in the source database.
pub type FileId = usize;

/// Source database.
/// Stores the source file contents for reference.
pub type SourceDatabase = files::SimpleFiles<String, String>;

#[derive(Debug, Default, Copy, Clone, Serialize, PartialEq, Eq, PartialOrd, Ord)]
pub struct SourceLocation {
    /// Byte offset into the file (counted from zero).
    pub offset: usize,
    /// Line number (counted from zero).
    pub line: usize,
    /// Column number (counted from zero)
    pub column: usize,
}

#[derive(Default, Copy, Clone, PartialEq, Eq, Serialize)]
pub struct SourceRange {
    pub file: FileId,
    pub start: SourceLocation,
    pub end: SourceLocation,
}

#[derive(Debug, Serialize, Clone)]
#[serde(tag = "kind", rename = "comment")]
pub struct Comment {
    pub loc: SourceRange,
    pub text: String,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize)]
#[serde(rename_all = "snake_case")]
pub enum EndiannessValue {
    LittleEndian,
    BigEndian,
}

#[derive(Debug, Copy, Clone, Serialize)]
#[serde(tag = "kind", rename = "endianness_declaration")]
pub struct Endianness {
    pub loc: SourceRange,
    pub value: EndiannessValue,
}

#[derive(Debug, Clone, Serialize)]
#[serde(tag = "kind", rename = "tag")]
pub struct TagValue {
    pub id: String,
    pub loc: SourceRange,
    pub value: usize,
}

#[derive(Debug, Clone, Serialize)]
#[serde(tag = "kind", rename = "tag")]
pub struct TagRange {
    pub id: String,
    pub loc: SourceRange,
    pub range: ops::RangeInclusive<usize>,
    pub tags: Vec<TagValue>,
}

#[derive(Debug, Clone, Serialize)]
#[serde(tag = "kind", rename = "tag")]
pub struct TagOther {
    pub id: String,
    pub loc: SourceRange,
}

#[derive(Debug, Serialize, Clone, PartialEq, Eq)]
#[serde(untagged)]
pub enum Tag {
    Value(TagValue),
    Range(TagRange),
    Other(TagOther),
}

#[derive(Debug, Serialize, Clone)]
#[serde(tag = "kind", rename = "constraint")]
pub struct Constraint {
    pub id: String,
    pub loc: SourceRange,
    pub value: Option<usize>,
    pub tag_id: Option<String>,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct FieldKey(pub usize);

#[derive(Debug, Serialize, Clone, PartialEq, Eq)]
#[serde(tag = "kind")]
pub enum FieldDesc {
    #[serde(rename = "checksum_field")]
    Checksum { field_id: String },
    #[serde(rename = "padding_field")]
    Padding { size: usize },
    #[serde(rename = "size_field")]
    Size { field_id: String, width: usize },
    #[serde(rename = "count_field")]
    Count { field_id: String, width: usize },
    #[serde(rename = "elementsize_field")]
    ElementSize { field_id: String, width: usize },
    #[serde(rename = "body_field")]
    Body,
    #[serde(rename = "payload_field")]
    Payload { size_modifier: Option<String> },
    #[serde(rename = "fixed_field")]
    FixedScalar { width: usize, value: usize },
    #[serde(rename = "fixed_field")]
    FixedEnum { enum_id: String, tag_id: String },
    #[serde(rename = "reserved_field")]
    Reserved { width: usize },
    #[serde(rename = "array_field")]
    Array {
        id: String,
        width: Option<usize>,
        type_id: Option<String>,
        size_modifier: Option<String>,
        size: Option<usize>,
    },
    #[serde(rename = "scalar_field")]
    Scalar { id: String, width: usize },
    /// Special case of Scalar for fields used as condition for
    /// optional fields. The width is always 1.
    #[serde(rename = "flag_field")]
    Flag { id: String, optional_field_id: String, set_value: usize },
    #[serde(rename = "typedef_field")]
    Typedef { id: String, type_id: String },
    #[serde(rename = "group_field")]
    Group { group_id: String, constraints: Vec<Constraint> },
}

#[derive(Debug, Serialize, Clone)]
pub struct Field {
    pub loc: SourceRange,
    /// Unique identifier used to refer to the AST node in
    /// compilation environments.
    #[serde(skip_serializing)]
    pub key: FieldKey,
    #[serde(flatten)]
    pub desc: FieldDesc,
    pub cond: Option<Constraint>,
}

#[derive(Debug, Serialize, Clone)]
#[serde(tag = "kind", rename = "test_case")]
pub struct TestCase {
    pub loc: SourceRange,
    pub input: String,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct DeclKey(pub usize);

#[derive(Debug, Serialize, Clone, PartialEq, Eq)]
#[serde(tag = "kind")]
pub enum DeclDesc {
    #[serde(rename = "checksum_declaration")]
    Checksum { id: String, function: String, width: usize },
    #[serde(rename = "custom_field_declaration")]
    CustomField { id: String, width: Option<usize>, function: String },
    #[serde(rename = "enum_declaration")]
    Enum { id: String, tags: Vec<Tag>, width: usize },
    #[serde(rename = "packet_declaration")]
    Packet {
        id: String,
        constraints: Vec<Constraint>,
        fields: Vec<Field>,
        parent_id: Option<String>,
    },
    #[serde(rename = "struct_declaration")]
    Struct {
        id: String,
        constraints: Vec<Constraint>,
        fields: Vec<Field>,
        parent_id: Option<String>,
    },
    #[serde(rename = "group_declaration")]
    Group { id: String, fields: Vec<Field> },
    #[serde(rename = "test_declaration")]
    Test { type_id: String, test_cases: Vec<TestCase> },
}

#[derive(Debug, Serialize, Clone)]
pub struct Decl {
    pub loc: SourceRange,
    /// Unique identifier used to refer to the AST node in
    /// compilation environments.
    #[serde(skip_serializing)]
    pub key: DeclKey,
    #[serde(flatten)]
    pub desc: DeclDesc,
}

#[derive(Debug, Serialize, Clone)]
pub struct File {
    pub version: String,
    pub file: FileId,
    pub comments: Vec<Comment>,
    pub endianness: Endianness,
    pub declarations: Vec<Decl>,
    #[serde(skip_serializing)]
    pub max_key: usize,
}

impl SourceLocation {
    /// Construct a new source location.
    ///
    /// The `line_starts` indicates the byte offsets where new lines
    /// start in the file. The first element should thus be `0` since
    /// every file has at least one line starting at offset `0`.
    pub fn new(offset: usize, line_starts: &[usize]) -> SourceLocation {
        let mut loc = SourceLocation { offset, line: 0, column: offset };
        for (line, start) in line_starts.iter().enumerate() {
            if *start > offset {
                break;
            }
            loc = SourceLocation { offset, line, column: offset - start };
        }
        loc
    }
}

impl SourceRange {
    pub fn primary(&self) -> diagnostic::Label<FileId> {
        diagnostic::Label::primary(self.file, self.start.offset..self.end.offset)
    }
    pub fn secondary(&self) -> diagnostic::Label<FileId> {
        diagnostic::Label::secondary(self.file, self.start.offset..self.end.offset)
    }
}

impl fmt::Display for SourceRange {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.start.line == self.end.line {
            write!(f, "{}:{}-{}", self.start.line, self.start.column, self.end.column)
        } else {
            write!(
                f,
                "{}:{}-{}:{}",
                self.start.line, self.start.column, self.end.line, self.end.column
            )
        }
    }
}

impl fmt::Debug for SourceRange {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("SourceRange").finish_non_exhaustive()
    }
}

impl ops::Add<SourceRange> for SourceRange {
    type Output = SourceRange;

    fn add(self, rhs: SourceRange) -> SourceRange {
        assert_eq!(self.file, rhs.file);
        SourceRange {
            file: self.file,
            start: self.start.min(rhs.start),
            end: self.end.max(rhs.end),
        }
    }
}

impl Eq for Endianness {}
impl PartialEq for Endianness {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out loc.
        self.value == other.value
    }
}

impl Eq for TagValue {}
impl PartialEq for TagValue {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out loc.
        self.id == other.id && self.value == other.value
    }
}

impl Eq for TagRange {}
impl PartialEq for TagRange {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out loc.
        self.id == other.id && self.range == other.range && self.tags == other.tags
    }
}

impl Eq for TagOther {}
impl PartialEq for TagOther {
    fn eq(&self, other: &Self) -> bool {
        // Implement structual equality, leave out loc.
        self.id == other.id
    }
}

impl Tag {
    pub fn id(&self) -> &str {
        match self {
            Tag::Value(TagValue { id, .. })
            | Tag::Range(TagRange { id, .. })
            | Tag::Other(TagOther { id, .. }) => id,
        }
    }

    pub fn loc(&self) -> &SourceRange {
        match self {
            Tag::Value(TagValue { loc, .. })
            | Tag::Range(TagRange { loc, .. })
            | Tag::Other(TagOther { loc, .. }) => loc,
        }
    }

    pub fn value(&self) -> Option<usize> {
        match self {
            Tag::Value(TagValue { value, .. }) => Some(*value),
            Tag::Range(_) | Tag::Other(_) => None,
        }
    }
}

impl Eq for Constraint {}
impl PartialEq for Constraint {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out loc.
        self.id == other.id && self.value == other.value && self.tag_id == other.tag_id
    }
}

impl Eq for TestCase {}
impl PartialEq for TestCase {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out loc.
        self.input == other.input
    }
}

impl Eq for File {}
impl PartialEq for File {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out comments and PDL
        // version information.
        self.endianness == other.endianness && self.declarations == other.declarations
    }
}

impl File {
    pub fn new(file: FileId) -> File {
        File {
            version: "1,0".to_owned(),
            comments: vec![],
            // The endianness is mandatory, so this default value will
            // be updated while parsing.
            endianness: Endianness {
                loc: SourceRange::default(),
                value: EndiannessValue::LittleEndian,
            },
            declarations: vec![],
            file,
            max_key: 0,
        }
    }

    /// Iterate over the children of the selected declaration.
    /// /!\ This method is unsafe to use if the file contains cyclic
    /// declarations, use with caution.
    pub fn iter_children<'d>(&'d self, decl: &'d Decl) -> impl Iterator<Item = &'d Decl> {
        self.declarations.iter().filter(|other_decl| other_decl.parent_id() == decl.id())
    }
}

impl Eq for Decl {}
impl PartialEq for Decl {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out loc and key.
        self.desc == other.desc
    }
}

impl Decl {
    pub fn id(&self) -> Option<&str> {
        match &self.desc {
            DeclDesc::Test { .. } => None,
            DeclDesc::Checksum { id, .. }
            | DeclDesc::CustomField { id, .. }
            | DeclDesc::Enum { id, .. }
            | DeclDesc::Packet { id, .. }
            | DeclDesc::Struct { id, .. }
            | DeclDesc::Group { id, .. } => Some(id),
        }
    }

    pub fn parent_id(&self) -> Option<&str> {
        match &self.desc {
            DeclDesc::Packet { parent_id, .. } | DeclDesc::Struct { parent_id, .. } => {
                parent_id.as_deref()
            }
            _ => None,
        }
    }

    pub fn constraints(&self) -> std::slice::Iter<'_, Constraint> {
        match &self.desc {
            DeclDesc::Packet { constraints, .. } | DeclDesc::Struct { constraints, .. } => {
                constraints.iter()
            }
            _ => [].iter(),
        }
    }

    pub fn fields(&self) -> std::slice::Iter<'_, Field> {
        match &self.desc {
            DeclDesc::Packet { fields, .. }
            | DeclDesc::Struct { fields, .. }
            | DeclDesc::Group { fields, .. } => fields.iter(),
            _ => [].iter(),
        }
    }

    /// Return the reference to the payload or body field in a declaration,
    /// if present.
    pub fn payload(&self) -> Option<&Field> {
        self.fields()
            .find(|field| matches!(&field.desc, FieldDesc::Payload { .. } | FieldDesc::Body { .. }))
    }

    /// Return the reference to the payload or body size field in a declaration,
    /// if present.
    pub fn payload_size(&self) -> Option<&Field> {
        self.fields().find(|field| match &field.desc {
            FieldDesc::Size { field_id, .. } => field_id == "_payload_" || field_id == "_body_",
            _ => false,
        })
    }

    /// Return the reference to the array size or count field in a declaration,
    /// if present.
    pub fn array_size(&self, id: &str) -> Option<&Field> {
        self.fields().find(|field| match &field.desc {
            FieldDesc::Size { field_id, .. } | FieldDesc::Count { field_id, .. } => field_id == id,
            _ => false,
        })
    }

    pub fn kind(&self) -> &str {
        match &self.desc {
            DeclDesc::Checksum { .. } => "checksum",
            DeclDesc::CustomField { .. } => "custom field",
            DeclDesc::Enum { .. } => "enum",
            DeclDesc::Packet { .. } => "packet",
            DeclDesc::Struct { .. } => "struct",
            DeclDesc::Group { .. } => "group",
            DeclDesc::Test { .. } => "test",
        }
    }
}

impl Eq for Field {}
impl PartialEq for Field {
    fn eq(&self, other: &Self) -> bool {
        // Implement structural equality, leave out loc and annot.
        self.desc == other.desc
    }
}

impl Field {
    pub fn id(&self) -> Option<&str> {
        match &self.desc {
            FieldDesc::Checksum { .. }
            | FieldDesc::Padding { .. }
            | FieldDesc::Size { .. }
            | FieldDesc::Count { .. }
            | FieldDesc::ElementSize { .. }
            | FieldDesc::Body
            | FieldDesc::Payload { .. }
            | FieldDesc::FixedScalar { .. }
            | FieldDesc::FixedEnum { .. }
            | FieldDesc::Reserved { .. }
            | FieldDesc::Group { .. } => None,
            FieldDesc::Array { id, .. }
            | FieldDesc::Scalar { id, .. }
            | FieldDesc::Flag { id, .. }
            | FieldDesc::Typedef { id, .. } => Some(id),
        }
    }

    pub fn kind(&self) -> &str {
        match &self.desc {
            FieldDesc::Checksum { .. } => "payload",
            FieldDesc::Padding { .. } => "padding",
            FieldDesc::Size { .. } => "size",
            FieldDesc::Count { .. } => "count",
            FieldDesc::ElementSize { .. } => "elementsize",
            FieldDesc::Body { .. } => "body",
            FieldDesc::Payload { .. } => "payload",
            FieldDesc::FixedScalar { .. } | FieldDesc::FixedEnum { .. } => "fixed",
            FieldDesc::Reserved { .. } => "reserved",
            FieldDesc::Group { .. } => "group",
            FieldDesc::Array { .. } => "array",
            FieldDesc::Scalar { .. } => "scalar",
            FieldDesc::Flag { .. } => "scalar",
            FieldDesc::Typedef { .. } => "typedef",
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn source_location_new() {
        let line_starts = &[0, 20, 80, 120, 150];
        assert_eq!(
            SourceLocation::new(0, line_starts),
            SourceLocation { offset: 0, line: 0, column: 0 }
        );
        assert_eq!(
            SourceLocation::new(10, line_starts),
            SourceLocation { offset: 10, line: 0, column: 10 }
        );
        assert_eq!(
            SourceLocation::new(50, line_starts),
            SourceLocation { offset: 50, line: 1, column: 30 }
        );
        assert_eq!(
            SourceLocation::new(100, line_starts),
            SourceLocation { offset: 100, line: 2, column: 20 }
        );
        assert_eq!(
            SourceLocation::new(1000, line_starts),
            SourceLocation { offset: 1000, line: 4, column: 850 }
        );
    }

    #[test]
    fn source_location_new_no_crash_with_empty_line_starts() {
        let loc = SourceLocation::new(100, &[]);
        assert_eq!(loc, SourceLocation { offset: 100, line: 0, column: 100 });
    }
}