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use okapi::openapi3::{Components, OpenApi, SchemaObject};
use okapi::schemars::schema::{InstanceType, Schema, SingleOrVec};

/// Parse OpenAPI 3 schema
pub fn parse_schema(file_content: &str) -> OpenApi {
    let schema = serde_yaml::from_str::<OpenApi>(file_content).expect("Failed to parse document");

    if schema.components.is_none() {
        log::error!("components is missing!");
        panic!()
    }

    schema
}

fn expect_single<E>(e: &SingleOrVec<E>) -> &E {
    match e {
        SingleOrVec::Single(e) => e,
        SingleOrVec::Vec(v) => &v[0],
    }
}

fn expect_schema_object(s: &Schema) -> &SchemaObject {
    match s {
        Schema::Bool(_) => {
            panic!("Got unexpected bool!");
        }
        Schema::Object(o) => o,
    }
}

#[derive(Debug, Clone, serde::Serialize)]
#[serde(tag = "type")]
pub enum NodeType {
    Null,
    Boolean,
    Array { item: Box<TreeNode> },
    Object { children: Vec<TreeNode> },
    String,
    Number,
    Integer,
}

#[derive(Debug, Clone, serde::Serialize)]
pub struct TreeNode {
    pub name: String,
    #[serde(flatten)]
    pub r#type: NodeType,
}

impl TreeNode {
    /// Merge two TreeNode
    pub fn merge_with(&self, other: &Self) -> Self {
        if !matches!(self.r#type, NodeType::String | NodeType::Object { .. }) {
            panic!("Cannot merge!");
        }

        if !matches!(other.r#type, NodeType::String | NodeType::Object { .. }) {
            panic!("Cannot merge other!");
        }

        let r#type = match (&self.r#type, &other.r#type) {
            (NodeType::String, NodeType::String) => NodeType::String,
            (NodeType::String, NodeType::Object { children })
            | (NodeType::Object { children }, NodeType::String) => NodeType::Object {
                children: children.clone(),
            },

            (NodeType::Object { children: c1 }, NodeType::Object { children: c2 }) => {
                let mut children = c1.clone();
                children.append(&mut c2.clone());
                NodeType::Object { children }
            }

            (_, _) => unreachable!(),
        };

        TreeNode {
            name: self.name.to_string(),
            r#type,
        }
    }
}

/// Construct the tree of a given structure name
pub fn build_tree(struct_name: &str, components: &Components) -> TreeNode {
    let schema = components
        .schemas
        .get(struct_name)
        .unwrap_or_else(|| panic!("Missing {struct_name}"));

    build_tree_schema(schema, struct_name, components)
}

/// Build a structure tree using a schema
fn build_tree_schema(
    schema: &SchemaObject,
    struct_name: &str,
    components: &Components,
) -> TreeNode {
    if let Some(name) = &schema.reference {
        return build_tree(
            name.strip_prefix("#/components/schemas/").unwrap(),
            components,
        );
    }

    if let Some(subschemas) = &schema.subschemas {
        if let Some(all_of) = &subschemas.all_of {
            assert!(!all_of.is_empty());
            let mut tree =
                build_tree_schema(expect_schema_object(&all_of[0]), struct_name, components);

            for other in all_of.iter().skip(1) {
                let other = build_tree_schema(expect_schema_object(other), struct_name, components);
                tree = tree.merge_with(&other);
            }

            return tree;
        } else {
            panic!("Unsupported case!");
        }
    }

    let schema_type = schema
        .instance_type
        .as_ref()
        .map(expect_single)
        .unwrap_or(&InstanceType::String);

    let r#type = match schema_type {
        InstanceType::Null => NodeType::Null,
        InstanceType::Boolean => NodeType::Boolean,
        InstanceType::Object => {
            let children = schema
                .object
                .as_ref()
                .map(|s| s.properties.clone())
                .unwrap_or_default()
                .iter()
                .map(|e| {
                    let o = expect_schema_object(e.1);
                    build_tree_schema(o, e.0, components)
                })
                .collect::<Vec<_>>();
            NodeType::Object { children }
        }
        InstanceType::Array => {
            let item = expect_schema_object(expect_single(
                schema.array.as_ref().unwrap().items.as_ref().unwrap(),
            ));
            NodeType::Array {
                item: Box::new(build_tree_schema(
                    item,
                    &format!("{struct_name}[]"),
                    components,
                )),
            }
        }
        InstanceType::Number => NodeType::Number,
        InstanceType::String => NodeType::String,
        InstanceType::Integer => NodeType::Integer,
    };

    TreeNode {
        name: struct_name.to_string(),
        r#type,
    }
}