oas3-gen 0.19.0

use std::collections::{BTreeMap, BTreeSet, HashMap};

use anyhow::Context;
use blake3::Hasher;
use json_canon::to_string as to_canonical_json;
use oas3::spec::ObjectSchema;
use serde_json::Value;

use super::{ConversionResult, REQUEST_BODY_SUFFIX, RESPONSE_PREFIX, RESPONSE_SUFFIX};
use crate::{generator::ast::RustType, reserved::to_rust_type_name};

pub(crate) struct SharedSchemaCache {
  schema_to_type: BTreeMap<String, String>,
  enum_to_type: HashMap<Vec<String>, String>,
  generated_types: Vec<RustType>,
  used_names: BTreeSet<String>,
  precomputed_names: BTreeMap<String, String>,
  precomputed_enum_names: HashMap<Vec<String>, String>,
}

impl SharedSchemaCache {
  pub(crate) fn new() -> Self {
    Self {
      schema_to_type: BTreeMap::new(),
      enum_to_type: HashMap::new(),
      generated_types: Vec::new(),
      used_names: BTreeSet::new(),
      precomputed_names: BTreeMap::new(),
      precomputed_enum_names: HashMap::new(),
    }
  }

  pub(crate) fn set_precomputed_names(
    &mut self,
    names: BTreeMap<String, String>,
    enum_names: HashMap<Vec<String>, String>,
  ) {
    self.precomputed_names = names;
    self.precomputed_enum_names = enum_names;
  }

  pub(crate) fn get_type_name(&self, schema: &ObjectSchema) -> ConversionResult<Option<String>> {
    let schema_hash = Self::hash_schema(schema)?;
    Ok(self.schema_to_type.get(&schema_hash).cloned())
  }

  pub(crate) fn get_enum_name(&self, values: &[String]) -> Option<String> {
    if let Some(name) = self.enum_to_type.get(values) {
      Some(name.clone())
    } else {
      self.precomputed_enum_names.get(values).cloned()
    }
  }

  pub(crate) fn is_enum_generated(&self, values: &[String]) -> bool {
    self.enum_to_type.contains_key(values)
  }

  pub(crate) fn register_enum(&mut self, values: Vec<String>, name: String) {
    self.enum_to_type.insert(values, name);
  }

  pub(crate) fn mark_name_used(&mut self, name: String) {
    self.used_names.insert(name);
  }

  pub(crate) fn get_preferred_name(&self, schema: &ObjectSchema, base_name: &str) -> ConversionResult<String> {
    let schema_hash = Self::hash_schema(schema)?;
    if let Some(name) = self.precomputed_names.get(&schema_hash) {
      return Ok(name.clone());
    }
    Ok(self.make_unique_name(base_name.to_string()))
  }

  pub(crate) fn register_type(
    &mut self,
    schema: &ObjectSchema,
    base_name: &str,
    mut nested_types: Vec<RustType>,
    type_def: RustType,
  ) -> ConversionResult<String> {
    let schema_hash = Self::hash_schema(schema)?;
    let mut name = base_name.to_string();

    if self.used_names.contains(&name) {
      // Check if it's an enum reuse case
      let mut reused = false;
      if !schema.enum_values.is_empty() {
        let mut values: Vec<String> = schema
          .enum_values
          .iter()
          .filter_map(|v| v.as_str().map(String::from))
          .collect();
        values.sort();
        if let Some(existing_name) = self.enum_to_type.get(&values)
          && existing_name == &name
        {
          reused = true;
        }
      }

      if reused {
        self.schema_to_type.insert(schema_hash, name.clone());
        return Ok(name);
      }

      if let Some(existing_name) = self.schema_to_type.get(&schema_hash) {
        return Ok(existing_name.clone());
      }
      name = self.make_unique_name(name);
    }

    self.used_names.insert(name.clone());
    self.schema_to_type.insert(schema_hash, name.clone());

    // If this is an enum, register its values too (if not already)
    if !schema.enum_values.is_empty() {
      let mut values: Vec<String> = schema
        .enum_values
        .iter()
        .filter_map(|v| v.as_str().map(String::from))
        .collect();
      values.sort();
      self.enum_to_type.insert(values, name.clone());
    }

    // Update the name in the struct/enum definition if we renamed it
    let mut final_type_def = type_def;
    match &mut final_type_def {
      RustType::Struct(s) => s.name.clone_from(&name),
      RustType::Enum(e) => e.name.clone_from(&name),
      _ => {}
    }

    self.generated_types.append(&mut nested_types);
    self.generated_types.push(final_type_def);

    Ok(name)
  }

  pub(crate) fn infer_name_from_context(schema: &ObjectSchema, path: &str, context: &str) -> String {
    let is_request = context == REQUEST_BODY_SUFFIX;

    let with_suffix = |base: &str| {
      if is_request {
        format!("{base}{REQUEST_BODY_SUFFIX}")
      } else {
        format!("{base}{context}{RESPONSE_SUFFIX}")
      }
    };

    if schema.properties.len() == 1
      && let Some((prop_name, _)) = schema.properties.iter().next()
    {
      let singular = cruet::to_singular(prop_name);
      return if is_request {
        singular
      } else {
        format!("{singular}{RESPONSE_SUFFIX}")
      };
    }

    let segments: Vec<_> = path
      .split('/')
      .filter(|s| !s.is_empty() && !s.starts_with('{'))
      .collect();

    segments
      .last()
      .map(|&s| with_suffix(&cruet::to_singular(s)))
      .or_else(|| segments.first().map(|&s| with_suffix(s)))
      .unwrap_or_else(|| {
        if is_request {
          REQUEST_BODY_SUFFIX.to_string()
        } else {
          format!("{RESPONSE_PREFIX}{context}")
        }
      })
  }

  pub(crate) fn make_unique_name(&self, base: String) -> String {
    let rust_name = to_rust_type_name(&base);
    if !self.used_names.contains(&rust_name) {
      return base;
    }

    let mut suffix = 2;
    while self.used_names.contains(&to_rust_type_name(&format!("{base}{suffix}"))) {
      suffix += 1;
    }
    format!("{base}{suffix}")
  }

  pub(crate) fn hash_schema(schema: &ObjectSchema) -> ConversionResult<String> {
    let mut value = serde_json::to_value(schema).context("Failed to serialize schema for hashing")?;

    Self::normalize_schema_semantics(&mut value);

    let canonical_json = to_canonical_json(&value).context("Failed to create canonical JSON string")?;

    let mut hasher = Hasher::new();
    hasher.update(canonical_json.as_bytes());
    let hash = hasher.finalize();

    Ok(hash.to_hex().to_string())
  }

  /// Normalizes a JSON schema `Value` in-place to ensure that
  /// semantically identical schemas produce the same hash.
  ///
  /// This function specifically handles fields where order does not
  /// matter, like the `required` and `type` arrays.
  fn normalize_schema_semantics(value: &mut Value) {
    match value {
      Value::Object(map) => {
        if let Some(Value::Array(arr)) = map.get_mut("required") {
          Self::sort_string_array_in_place(arr);
        }

        if let Some(Value::Array(arr)) = map.get_mut("type") {
          Self::sort_string_array_in_place(arr);
        }

        if let Some(Value::Array(arr)) = map.get_mut("enum") {
          Self::sort_string_array_in_place(arr);
        }

        for value in map.values_mut() {
          Self::normalize_schema_semantics(value);
        }
      }
      Value::Array(arr) => {
        for item in arr {
          Self::normalize_schema_semantics(item);
        }
      }
      _ => {}
    }
  }

  /// Helper to sort a `Vec<Value>` in-place, if and only if
  /// it contains entirely string elements.
  fn sort_string_array_in_place(arr: &mut Vec<Value>) {
    let mut strings: Vec<String> = arr.iter().filter_map(|v| v.as_str().map(String::from)).collect();

    if strings.len() == arr.len() {
      strings.sort_unstable();
      *arr = strings.into_iter().map(Value::String).collect();
    }
  }

  pub(crate) fn into_types(self) -> Vec<RustType> {
    self.generated_types
  }
}

#[cfg(test)]
mod tests {
  use oas3::spec::ObjectSchema;

  use super::*;

  #[test]
  fn test_hash_schema_deterministic() {
    let schema = ObjectSchema {
      required: vec!["name".to_string(), "id".to_string()],
      ..Default::default()
    };

    let hash1 = SharedSchemaCache::hash_schema(&schema).expect("hash should succeed");
    let hash2 = SharedSchemaCache::hash_schema(&schema).expect("hash should succeed");
    let hash3 = SharedSchemaCache::hash_schema(&schema).expect("hash should succeed");

    assert_eq!(hash1, hash2, "Hash should be deterministic across calls");
    assert_eq!(hash2, hash3, "Hash should be deterministic across calls");
    assert!(!hash1.is_empty(), "Hash should not be empty");
  }

  #[test]
  fn test_hash_schema_different_for_different_schemas() {
    let schema1 = ObjectSchema {
      required: vec!["id".to_string()],
      ..Default::default()
    };

    let schema2 = ObjectSchema {
      required: vec!["name".to_string()],
      ..Default::default()
    };

    let hash1 = SharedSchemaCache::hash_schema(&schema1).expect("hash should succeed");
    let hash2 = SharedSchemaCache::hash_schema(&schema2).expect("hash should succeed");

    assert_ne!(hash1, hash2, "Different schemas should produce different hashes");
  }

  #[test]
  fn test_hash_schema_order_independent() {
    let schema1 = ObjectSchema {
      required: vec!["id".to_string(), "name".to_string()],
      ..Default::default()
    };

    let schema2 = ObjectSchema {
      required: vec!["name".to_string(), "id".to_string()],
      ..Default::default()
    };

    let hash1 = SharedSchemaCache::hash_schema(&schema1).expect("hash should succeed");
    let hash2 = SharedSchemaCache::hash_schema(&schema2).expect("hash should succeed");

    assert_eq!(
      hash1, hash2,
      "Required array order should not affect hash due to RFC 8785 canonicalization"
    );
  }
}