use std::{borrow::Cow, collections::HashMap, path::Path, str};

use anyhow::Context;
use memofs::Vfs;
use serde::Deserialize;

use crate::{
    resolution::UnresolvedValue,
    snapshot::{InstanceContext, InstanceSnapshot},
};

use super::util::PathExt;

pub fn snapshot_json_model(
    context: &InstanceContext,
    vfs: &Vfs,
    path: &Path,
) -> anyhow::Result<Option<InstanceSnapshot>> {
    let name = path.file_name_trim_end(".model.json")?;

    let contents = vfs.read(path)?;
    let contents_str = str::from_utf8(&contents)
        .with_context(|| format!("File was not valid UTF-8: {}", path.display()))?;

    if contents_str.trim().is_empty() {
        return Ok(None);
    }

    let mut instance: JsonModel = serde_json::from_str(contents_str)
        .with_context(|| format!("File is not a valid JSON model: {}", path.display()))?;

    if let Some(top_level_name) = &instance.name {
        let new_name = format!("{}.model.json", top_level_name);

        log::warn!(
            "Model at path {} had a top-level Name field. \
            This field has been ignored since Rojo 6.0.\n\
            Consider removing this field and renaming the file to {}.",
            new_name,
            path.display()
        );
    }

    instance.name = Some(name.to_owned());

    let mut snapshot = instance
        .into_snapshot()
        .with_context(|| format!("Could not load JSON model: {}", path.display()))?;

    snapshot.metadata = snapshot
        .metadata
        .instigating_source(path)
        .relevant_paths(vec![path.to_path_buf()])
        .context(context);

    Ok(Some(snapshot))
}

#[derive(Debug, Deserialize)]
#[serde(rename_all = "camelCase")]
struct JsonModel {
    #[serde(alias = "Name")]
    name: Option<String>,

    #[serde(alias = "ClassName")]
    class_name: String,

    #[serde(
        alias = "Children",
        default = "Vec::new",
        skip_serializing_if = "Vec::is_empty"
    )]
    children: Vec<JsonModel>,

    #[serde(
        alias = "Properties",
        default = "HashMap::new",
        skip_serializing_if = "HashMap::is_empty"
    )]
    properties: HashMap<String, UnresolvedValue>,
}

impl JsonModel {
    fn into_snapshot(self) -> anyhow::Result<InstanceSnapshot> {
        let name = self.name.unwrap_or_else(|| self.class_name.clone());
        let class_name = self.class_name;

        let mut children = Vec::with_capacity(self.children.len());
        for child in self.children {
            children.push(child.into_snapshot()?);
        }

        let mut properties = HashMap::with_capacity(self.properties.len());
        for (key, unresolved) in self.properties {
            let value = unresolved.resolve(&class_name, &key)?;
            properties.insert(key, value);
        }

        Ok(InstanceSnapshot {
            snapshot_id: None,
            metadata: Default::default(),
            name: Cow::Owned(name),
            class_name: Cow::Owned(class_name),
            properties,
            children,
        })
    }
}

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

    use memofs::{InMemoryFs, VfsSnapshot};

    #[test]
    fn model_from_vfs() {
        let mut imfs = InMemoryFs::new();
        imfs.load_snapshot(
            "/foo.model.json",
            VfsSnapshot::file(
                r#"
                    {
                      "className": "IntValue",
                      "properties": {
                        "Value": 5
                      },
                      "children": [
                        {
                          "name": "The Child",
                          "className": "StringValue"
                        }
                      ]
                    }
                "#,
            ),
        )
        .unwrap();

        let vfs = Vfs::new(imfs);

        let instance_snapshot = snapshot_json_model(
            &InstanceContext::default(),
            &vfs,
            Path::new("/foo.model.json"),
        )
        .unwrap()
        .unwrap();

        insta::assert_yaml_snapshot!(instance_snapshot);
    }

    #[test]
    fn model_from_vfs_legacy() {
        let mut imfs = InMemoryFs::new();
        imfs.load_snapshot(
            "/foo.model.json",
            VfsSnapshot::file(
                r#"
                    {
                      "ClassName": "IntValue",
                      "Properties": {
                        "Value": 5
                      },
                      "Children": [
                        {
                          "Name": "The Child",
                          "ClassName": "StringValue"
                        }
                      ]
                    }
                "#,
            ),
        )
        .unwrap();

        let vfs = Vfs::new(imfs);

        let instance_snapshot = snapshot_json_model(
            &InstanceContext::default(),
            &vfs,
            Path::new("/foo.model.json"),
        )
        .unwrap()
        .unwrap();

        insta::assert_yaml_snapshot!(instance_snapshot);
    }
}