/*
 * Copyright (C) 2023 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

use anyhow::Result;
use serde::Serialize;
use std::path::PathBuf;
use tinytemplate::TinyTemplate;

use crate::codegen;
use crate::commands::OutputFile;
use crate::protos::{ProtoFlagPermission, ProtoFlagState, ProtoParsedFlag};

pub fn generate_java_code<'a, I>(package: &str, parsed_flags_iter: I) -> Result<Vec<OutputFile>>
where
    I: Iterator<Item = &'a ProtoParsedFlag>,
{
    let class_elements: Vec<ClassElement> =
        parsed_flags_iter.map(|pf| create_class_element(package, pf)).collect();
    let is_read_write = class_elements.iter().any(|elem| elem.is_read_write);
    let context = Context { package_name: package.to_string(), is_read_write, class_elements };
    let mut template = TinyTemplate::new();
    template.add_template("Flags.java", include_str!("../templates/Flags.java.template"))?;
    template.add_template(
        "FeatureFlagsImpl.java",
        include_str!("../templates/FeatureFlagsImpl.java.template"),
    )?;
    template.add_template(
        "FeatureFlags.java",
        include_str!("../templates/FeatureFlags.java.template"),
    )?;

    let path: PathBuf = package.split('.').collect();
    ["Flags.java", "FeatureFlagsImpl.java", "FeatureFlags.java"]
        .iter()
        .map(|file| {
            Ok(OutputFile {
                contents: template.render(file, &context)?.into(),
                path: path.join(file),
            })
        })
        .collect::<Result<Vec<OutputFile>>>()
}

#[derive(Serialize)]
struct Context {
    pub package_name: String,
    pub is_read_write: bool,
    pub class_elements: Vec<ClassElement>,
}

#[derive(Serialize)]
struct ClassElement {
    pub default_value: String,
    pub device_config_namespace: String,
    pub device_config_flag: String,
    pub flag_name_constant_suffix: String,
    pub is_read_write: bool,
    pub method_name: String,
}

fn create_class_element(package: &str, pf: &ProtoParsedFlag) -> ClassElement {
    let device_config_flag = codegen::create_device_config_ident(package, pf.name())
        .expect("values checked at flag parse time");
    ClassElement {
        default_value: if pf.state() == ProtoFlagState::ENABLED {
            "true".to_string()
        } else {
            "false".to_string()
        },
        device_config_namespace: pf.namespace().to_string(),
        device_config_flag,
        flag_name_constant_suffix: pf.name().to_ascii_uppercase(),
        is_read_write: pf.permission() == ProtoFlagPermission::READ_WRITE,
        method_name: format_java_method_name(pf.name()),
    }
}

fn format_java_method_name(flag_name: &str) -> String {
    flag_name
        .split('_')
        .filter(|&word| !word.is_empty())
        .enumerate()
        .map(|(index, word)| {
            if index == 0 {
                word.to_ascii_lowercase()
            } else {
                word[0..1].to_ascii_uppercase() + &word[1..].to_ascii_lowercase()
            }
        })
        .collect::<Vec<String>>()
        .join("")
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::collections::HashMap;

    #[test]
    fn test_generate_java_code() {
        let parsed_flags = crate::test::parse_test_flags();
        let generated_files =
            generate_java_code(crate::test::TEST_PACKAGE, parsed_flags.parsed_flag.iter()).unwrap();
        let expect_flags_content = r#"
        package com.android.aconfig.test;
        public final class Flags {
            public static final String FLAG_DISABLED_RO = "com.android.aconfig.test.disabled_ro";
            public static final String FLAG_DISABLED_RW = "com.android.aconfig.test.disabled_rw";
            public static final String FLAG_ENABLED_RO = "com.android.aconfig.test.enabled_ro";
            public static final String FLAG_ENABLED_RW = "com.android.aconfig.test.enabled_rw";

            public static boolean disabledRo() {
                return FEATURE_FLAGS.disabledRo();
            }
            public static boolean disabledRw() {
                return FEATURE_FLAGS.disabledRw();
            }
            public static boolean enabledRo() {
                return FEATURE_FLAGS.enabledRo();
            }
            public static boolean enabledRw() {
                return FEATURE_FLAGS.enabledRw();
            }
            private static FeatureFlags FEATURE_FLAGS = new FeatureFlagsImpl();
        }
        "#;
        let expected_featureflagsimpl_content = r#"
        package com.android.aconfig.test;
        import android.provider.DeviceConfig;
        public final class FeatureFlagsImpl implements FeatureFlags {
            @Override
            public boolean disabledRo() {
                return false;
            }
            @Override
            public boolean disabledRw() {
                return DeviceConfig.getBoolean(
                    "aconfig_test",
                    "com.android.aconfig.test.disabled_rw",
                    false
                );
            }
            @Override
            public boolean enabledRo() {
                return true;
            }
            @Override
            public boolean enabledRw() {
                return DeviceConfig.getBoolean(
                    "aconfig_test",
                    "com.android.aconfig.test.enabled_rw",
                    true
                );
            }
        }
        "#;
        let expected_featureflags_content = r#"
        package com.android.aconfig.test;
        public interface FeatureFlags {
            boolean disabledRo();
            boolean disabledRw();
            boolean enabledRo();
            boolean enabledRw();
        }
        "#;
        let mut file_set = HashMap::from([
            ("com/android/aconfig/test/Flags.java", expect_flags_content),
            ("com/android/aconfig/test/FeatureFlagsImpl.java", expected_featureflagsimpl_content),
            ("com/android/aconfig/test/FeatureFlags.java", expected_featureflags_content),
        ]);

        for file in generated_files {
            let file_path = file.path.to_str().unwrap();
            assert!(file_set.contains_key(file_path), "Cannot find {}", file_path);
            assert_eq!(
                None,
                crate::test::first_significant_code_diff(
                    file_set.get(file_path).unwrap(),
                    &String::from_utf8(file.contents.clone()).unwrap()
                ),
                "File {} content is not correct",
                file_path
            );
            file_set.remove(file_path);
        }

        assert!(file_set.is_empty());
    }

    #[test]
    fn test_format_java_method_name() {
        let input = "____some_snake___name____";
        let expected = "someSnakeName";
        let formatted_name = format_java_method_name(input);
        assert_eq!(expected, formatted_name);
    }
}