//! Error types for the semantic analysis phase of the compiler.

#![allow(missing_docs)]

use std::{collections::HashSet, fmt::Display};

use getset::Getters;
use itertools::Itertools as _;

use crate::{
    base::{
        log::{Message, Severity, SourceCodeDisplay},
        source_file::{SourceElement as _, Span},
    },
    lexical::token::StringLiteral,
    syntax::syntax_tree::expression::Expression,
};

#[derive(Debug, Clone, PartialEq, Eq, Hash, thiserror::Error)]
#[allow(missing_docs)]
pub enum Error {
    #[error(transparent)]
    MissingFunctionDeclaration(#[from] MissingFunctionDeclaration),
    #[error(transparent)]
    UnexpectedExpression(#[from] UnexpectedExpression),
    #[error(transparent)]
    ConflictingFunctionNames(#[from] ConflictingFunctionNames),
    #[error(transparent)]
    InvalidNamespaceName(#[from] InvalidNamespaceName),
    #[error(transparent)]
    UnresolvedMacroUsage(#[from] UnresolvedMacroUsage),
    #[error(transparent)]
    IncompatibleFunctionAnnotation(#[from] IncompatibleFunctionAnnotation),
}

/// An error that occurs when a function declaration is missing.
#[derive(Debug, Clone, PartialEq, Eq, Hash, Getters)]
pub struct MissingFunctionDeclaration {
    #[get = "pub"]
    span: Span,
    #[get = "pub"]
    alternatives: Vec<String>,
}

impl MissingFunctionDeclaration {
    pub(super) fn from_context(identifier_span: Span, functions: &HashSet<String>) -> Self {
        let own_name = identifier_span.str();
        let alternatives = functions
            .iter()
            .filter_map(|function_name| {
                let normalized_distance =
                    strsim::normalized_damerau_levenshtein(own_name, function_name);
                (normalized_distance > 0.8
                    || strsim::damerau_levenshtein(own_name, function_name) < 3)
                    .then_some((normalized_distance, function_name))
            })
            .sorted_by(|a, b| a.0.partial_cmp(&b.0).unwrap_or(std::cmp::Ordering::Equal))
            .map(|(_, data)| data)
            .take(8)
            .cloned()
            .collect::<Vec<_>>();

        Self {
            alternatives,
            span: identifier_span,
        }
    }
}

impl Display for MissingFunctionDeclaration {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        use std::fmt::Write;

        let message = format!(
            "no matching function declaration found for invocation of function `{}`",
            self.span.str()
        );
        write!(f, "{}", Message::new(Severity::Error, message))?;

        let help_message = if self.alternatives.is_empty() {
            None
        } else {
            let mut message = String::from("did you mean ");
            for (i, alternative) in self.alternatives.iter().enumerate() {
                if i > 0 {
                    message.push_str(", ");
                }
                write!(message, "`{alternative}`")?;
            }
            Some(message + "?")
        };

        write!(
            f,
            "\n{}",
            SourceCodeDisplay::new(&self.span, help_message.as_ref())
        )
    }
}

impl std::error::Error for MissingFunctionDeclaration {}

/// An error that occurs when a function declaration is missing.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct UnexpectedExpression(pub Expression);

impl Display for UnexpectedExpression {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            Message::new(Severity::Error, "encountered unexpected expression")
        )?;

        write!(
            f,
            "\n{}",
            SourceCodeDisplay::new(&self.0.span(), Option::<u8>::None)
        )
    }
}

impl std::error::Error for UnexpectedExpression {}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct ConflictingFunctionNames {
    pub definition: Span,
    pub name: String,
}

impl Display for ConflictingFunctionNames {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            Message::new(
                Severity::Error,
                format!("the following function declaration conflicts with an existing function with name `{}`", self.name)
            )
        )?;

        write!(
            f,
            "\n{}",
            SourceCodeDisplay::new(&self.definition, Option::<u8>::None)
        )
    }
}

impl std::error::Error for ConflictingFunctionNames {}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct InvalidNamespaceName {
    pub name: StringLiteral,
    pub invalid_chars: String,
}

impl Display for InvalidNamespaceName {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            Message::new(
                Severity::Error,
                format!(
                    "Invalid characters in namespace `{}`. The following characters are not allowed in namespace definitions: `{}`",
                    self.name.str_content(),
                    self.invalid_chars
                )
            )
        )?;

        write!(
            f,
            "\n{}",
            SourceCodeDisplay::new(&self.name.span, Option::<u8>::None)
        )
    }
}

impl std::error::Error for InvalidNamespaceName {}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct UnresolvedMacroUsage {
    pub span: Span,
}

impl Display for UnresolvedMacroUsage {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            Message::new(
                Severity::Error,
                format!(
                    "Macro `{}` was used, but could not be resolved.",
                    self.span.str(),
                )
            )
        )?;

        write!(
            f,
            "\n{}",
            SourceCodeDisplay::new(
                &self.span,
                Some(format!(
                    "You might want to add `{}` to the function parameters.",
                    self.span.str()
                ))
            )
        )
    }
}

impl std::error::Error for UnresolvedMacroUsage {}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct IncompatibleFunctionAnnotation {
    pub span: Span,
    pub reason: String,
}

impl Display for IncompatibleFunctionAnnotation {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            Message::new(
                Severity::Error,
                format!(
                    "Annotation `{}` cannot be used here, because {}.",
                    self.span.str(),
                    self.reason
                )
            )
        )?;

        write!(f, "\n{}", SourceCodeDisplay::new(&self.span, None::<u8>))
    }
}

impl std::error::Error for IncompatibleFunctionAnnotation {}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct InvalidFunctionArguments {
    pub span: Span,
    pub expected: usize,
    pub actual: usize,
}

impl Display for InvalidFunctionArguments {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            Message::new(
                Severity::Error,
                format!(
                    "Expected {} arguments, but got {}.",
                    self.expected, self.actual
                )
            )
        )?;

        let help_message = if self.expected > self.actual {
            format!(
                "You might want to add {} more arguments.",
                self.expected - self.actual
            )
        } else {
            format!(
                "You might want to remove {} arguments.",
                self.actual - self.expected
            )
        };

        write!(
            f,
            "\n{}",
            SourceCodeDisplay::new(&self.span, Some(help_message))
        )
    }
}

impl std::error::Error for InvalidFunctionArguments {}