use std::fmt::{self, Debug};

use anyhow::Result;

use wasm_encoder::Encode;

use wasm_encoder::reencode::{Reencode, RoundtripReencoder};

use wasmparser::{BinaryReader, NameSectionReader};

/// Helper for rewriting a module's name section with a new module name.

pub struct ModuleNames<'a> {

    module_name: Option<String>,

    names: Vec<wasmparser::Name<'a>>,

}

impl<'a> Debug for ModuleNames<'a> {

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        f.debug_struct("ModuleNames")

            .field("module_name", &self.module_name)

            .finish_non_exhaustive()

    }

}

impl<'a> ModuleNames<'a> {

    /// Create an empty name section.

    pub fn empty() -> Self {

        ModuleNames {

            module_name: None,

            names: Vec::new(),

        }

    }

    /// Read a name section from a WebAssembly binary. Records the module name, and all other

    /// contents of name section, for later serialization.

    pub fn from_bytes(bytes: &'a [u8], offset: u64) -> Result<ModuleNames<'a>> {

        let reader = BinaryReader::new(bytes, offset);

        let section = NameSectionReader::new(reader);

        let mut s = Self::empty();

        for name in section.into_iter() {

            let name = name?;

            match name {

                wasmparser::Name::Module { name, .. } => s.module_name = Some(name.to_owned()),

                _ => s.names.push(name),

            }

        }

        Ok(s)

    }

    /// Update module section according to [`AddMetadata`]

    pub(crate) fn from_name(name: &Option<String>) -> Self {

        let mut s = Self::empty();

        s.module_name = name.clone();

        s

    }

    /// Merge with another section

    pub(crate) fn merge(&mut self, other: &Self) {

        if other.module_name.is_some() {

            self.module_name = other.module_name.clone();

        }

        self.names.extend_from_slice(&other.names);

    }

    /// Set module name

    pub fn set_name(&mut self, name: &str) {

        self.module_name = Some(name.to_owned())

    }

    /// Get module name

    pub fn get_name(&self) -> Option<&String> {

        self.module_name.as_ref()

    }

    /// Serialize into [`wasm_encoder::NameSection`].

    pub(crate) fn section(&self) -> Result<wasm_encoder::NameSection> {

        let mut section = wasm_encoder::NameSection::new();

        if let Some(module_name) = &self.module_name {

            section.module(&module_name);

        }

        for n in self.names.iter() {

            RoundtripReencoder.parse_custom_name_subsection(&mut section, n.clone())?;

        }

        Ok(section)

    }

    /// Serialize into the raw bytes of a wasm custom section.

    pub fn raw_custom_section(&self) -> Result<Vec<u8>> {

        let mut ret = Vec::new();

        self.section()?.encode(&mut ret);

        Ok(ret)

    }

}