// Copyright 2020 The Jujutsu Authors
//
// 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
//
// https://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 itertools::Itertools as _;
use jujutsu_lib::backend::{Signature, Timestamp};
use jujutsu_lib::commit::Commit;
use jujutsu_lib::op_store::WorkspaceId;
use jujutsu_lib::repo::RepoRef;
use jujutsu_lib::rewrite;
use pest::iterators::{Pair, Pairs};
use pest::Parser;
use pest_derive::Parser;

use crate::templater::{
    BranchProperty, CommitOrChangeId, ConditionalTemplate, FormattablePropertyTemplate,
    GitHeadProperty, GitRefsProperty, IdWithHighlightedPrefix, IsWorkingCopyProperty,
    LabelTemplate, ListTemplate, Literal, PlainTextFormattedProperty, TagProperty, Template,
    TemplateFunction, TemplateProperty, TemplatePropertyFn, WorkingCopiesProperty,
};
use crate::{cli_util, time_util};

#[derive(Parser)]
#[grammar = "template.pest"]
pub struct TemplateParser;

fn parse_string_literal(pair: Pair<Rule>) -> String {
    assert_eq!(pair.as_rule(), Rule::literal);
    let mut result = String::new();
    for part in pair.into_inner() {
        match part.as_rule() {
            Rule::raw_literal => {
                result.push_str(part.as_str());
            }
            Rule::escape => match part.as_str().as_bytes()[1] as char {
                '"' => result.push('"'),
                '\\' => result.push('\\'),
                'n' => result.push('\n'),
                char => panic!("invalid escape: \\{char:?}"),
            },
            _ => panic!("unexpected part of string: {part:?}"),
        }
    }
    result
}

enum Property<'a, I> {
    String(Box<dyn TemplateProperty<I, Output = String> + 'a>),
    Boolean(Box<dyn TemplateProperty<I, Output = bool> + 'a>),
    CommitOrChangeId(Box<dyn TemplateProperty<I, Output = CommitOrChangeId<'a>> + 'a>),
    IdWithHighlightedPrefix(Box<dyn TemplateProperty<I, Output = IdWithHighlightedPrefix> + 'a>),
    Signature(Box<dyn TemplateProperty<I, Output = Signature> + 'a>),
    Timestamp(Box<dyn TemplateProperty<I, Output = Timestamp> + 'a>),
}

impl<'a, I: 'a> Property<'a, I> {
    fn after<C: 'a>(self, first: Box<dyn TemplateProperty<C, Output = I> + 'a>) -> Property<'a, C> {
        fn chain<'a, C: 'a, I: 'a, O: 'a>(
            first: Box<dyn TemplateProperty<C, Output = I> + 'a>,
            second: Box<dyn TemplateProperty<I, Output = O> + 'a>,
        ) -> Box<dyn TemplateProperty<C, Output = O> + 'a> {
            Box::new(TemplateFunction::new(first, move |value| {
                second.extract(&value)
            }))
        }
        match self {
            Property::String(property) => Property::String(chain(first, property)),
            Property::Boolean(property) => Property::Boolean(chain(first, property)),
            Property::CommitOrChangeId(property) => {
                Property::CommitOrChangeId(chain(first, property))
            }
            Property::IdWithHighlightedPrefix(property) => {
                Property::IdWithHighlightedPrefix(chain(first, property))
            }
            Property::Signature(property) => Property::Signature(chain(first, property)),
            Property::Timestamp(property) => Property::Timestamp(chain(first, property)),
        }
    }

    fn try_into_boolean(self) -> Option<Box<dyn TemplateProperty<I, Output = bool> + 'a>> {
        match self {
            Property::String(property) => {
                Some(Box::new(TemplateFunction::new(property, |s| !s.is_empty())))
            }
            Property::Boolean(property) => Some(property),
            _ => None,
        }
    }

    fn into_plain_text(self) -> Box<dyn TemplateProperty<I, Output = String> + 'a> {
        match self {
            Property::String(property) => property,
            _ => Box::new(PlainTextFormattedProperty::new(self.into_template())),
        }
    }

    fn into_template(self) -> Box<dyn Template<I> + 'a> {
        fn wrap<'a, I: 'a, O: Template<()> + 'a>(
            property: Box<dyn TemplateProperty<I, Output = O> + 'a>,
        ) -> Box<dyn Template<I> + 'a> {
            Box::new(FormattablePropertyTemplate::new(property))
        }
        match self {
            Property::String(property) => wrap(property),
            Property::Boolean(property) => wrap(property),
            Property::CommitOrChangeId(property) => wrap(property),
            Property::IdWithHighlightedPrefix(property) => wrap(property),
            Property::Signature(property) => wrap(property),
            Property::Timestamp(property) => wrap(property),
        }
    }
}

struct PropertyAndLabels<'a, C>(Property<'a, C>, Vec<String>);

impl<'a, C: 'a> PropertyAndLabels<'a, C> {
    fn into_template(self) -> Box<dyn Template<C> + 'a> {
        let PropertyAndLabels(property, labels) = self;
        if labels.is_empty() {
            property.into_template()
        } else {
            Box::new(LabelTemplate::new(
                property.into_template(),
                Literal(labels),
            ))
        }
    }
}

enum Expression<'a, C> {
    Property(PropertyAndLabels<'a, C>),
    Template(Box<dyn Template<C> + 'a>),
}

impl<'a, C: 'a> Expression<'a, C> {
    fn try_into_boolean(self) -> Option<Box<dyn TemplateProperty<C, Output = bool> + 'a>> {
        match self {
            Expression::Property(PropertyAndLabels(property, _)) => property.try_into_boolean(),
            Expression::Template(_) => None,
        }
    }

    fn into_plain_text(self) -> Box<dyn TemplateProperty<C, Output = String> + 'a> {
        match self {
            Expression::Property(PropertyAndLabels(property, _)) => property.into_plain_text(),
            Expression::Template(template) => Box::new(PlainTextFormattedProperty::new(template)),
        }
    }

    fn into_template(self) -> Box<dyn Template<C> + 'a> {
        match self {
            Expression::Property(property_labels) => property_labels.into_template(),
            Expression::Template(template) => template,
        }
    }
}

fn parse_method_chain<'a, I: 'a>(
    pair: Pair<Rule>,
    input_property: PropertyAndLabels<'a, I>,
) -> PropertyAndLabels<'a, I> {
    let PropertyAndLabels(mut property, mut labels) = input_property;
    assert_eq!(pair.as_rule(), Rule::maybe_method);
    for chain in pair.into_inner() {
        assert_eq!(chain.as_rule(), Rule::function);
        let (name, args) = {
            let mut inner = chain.into_inner();
            let name = inner.next().unwrap();
            let args_pair = inner.next().unwrap();
            assert_eq!(name.as_rule(), Rule::identifier);
            assert_eq!(args_pair.as_rule(), Rule::function_arguments);
            (name, args_pair.into_inner())
        };
        labels.push(name.as_str().to_owned());
        property = match property {
            Property::String(property) => parse_string_method(name, args).after(property),
            Property::Boolean(property) => parse_boolean_method(name, args).after(property),
            Property::CommitOrChangeId(property) => {
                parse_commit_or_change_id_method(name, args).after(property)
            }
            Property::IdWithHighlightedPrefix(_property) => {
                panic!("Commit or change ids with styled prefix don't have any methods")
            }
            Property::Signature(property) => parse_signature_method(name, args).after(property),
            Property::Timestamp(property) => parse_timestamp_method(name, args).after(property),
        };
    }
    PropertyAndLabels(property, labels)
}

fn parse_string_method<'a>(name: Pair<Rule>, _args: Pairs<Rule>) -> Property<'a, String> {
    fn wrap_fn<'a, O>(
        f: impl Fn(&String) -> O + 'a,
    ) -> Box<dyn TemplateProperty<String, Output = O> + 'a> {
        Box::new(TemplatePropertyFn(f))
    }
    // TODO: validate arguments
    match name.as_str() {
        "first_line" => Property::String(wrap_fn(|s| {
            s.lines().next().unwrap_or_default().to_string()
        })),
        name => panic!("no such string method: {name}"),
    }
}

fn parse_boolean_method<'a>(name: Pair<Rule>, _args: Pairs<Rule>) -> Property<'a, bool> {
    // TODO: validate arguments
    panic!("no such boolean method: {}", name.as_str());
}

fn parse_commit_or_change_id_method<'a>(
    name: Pair<Rule>,
    _args: Pairs<Rule>,
) -> Property<'a, CommitOrChangeId<'a>> {
    fn wrap_fn<'a, O>(
        f: impl Fn(&CommitOrChangeId<'a>) -> O + 'a,
    ) -> Box<dyn TemplateProperty<CommitOrChangeId<'a>, Output = O> + 'a> {
        Box::new(TemplatePropertyFn(f))
    }
    // TODO: validate arguments
    match name.as_str() {
        "short" => Property::String(wrap_fn(|id| id.short())),
        "shortest_prefix_and_brackets" => {
            Property::String(wrap_fn(|id| id.shortest_prefix_and_brackets()))
        }
        "shortest_styled_prefix" => {
            Property::IdWithHighlightedPrefix(wrap_fn(|id| id.shortest_styled_prefix()))
        }
        name => panic!("no such commit ID method: {name}"),
    }
}

fn parse_signature_method<'a>(name: Pair<Rule>, _args: Pairs<Rule>) -> Property<'a, Signature> {
    fn wrap_fn<'a, O>(
        f: impl Fn(&Signature) -> O + 'a,
    ) -> Box<dyn TemplateProperty<Signature, Output = O> + 'a> {
        Box::new(TemplatePropertyFn(f))
    }
    // TODO: validate arguments
    match name.as_str() {
        "name" => Property::String(wrap_fn(|signature| signature.name.clone())),
        "email" => Property::String(wrap_fn(|signature| signature.email.clone())),
        "timestamp" => Property::Timestamp(wrap_fn(|signature| signature.timestamp.clone())),
        name => panic!("no such commit ID method: {name}"),
    }
}

fn parse_timestamp_method<'a>(name: Pair<Rule>, _args: Pairs<Rule>) -> Property<'a, Timestamp> {
    fn wrap_fn<'a, O>(
        f: impl Fn(&Timestamp) -> O + 'a,
    ) -> Box<dyn TemplateProperty<Timestamp, Output = O> + 'a> {
        Box::new(TemplatePropertyFn(f))
    }
    // TODO: validate arguments
    match name.as_str() {
        "ago" => Property::String(wrap_fn(time_util::format_timestamp_relative_to_now)),
        name => panic!("no such timestamp method: {name}"),
    }
}

fn parse_commit_keyword<'a>(
    repo: RepoRef<'a>,
    workspace_id: &WorkspaceId,
    pair: Pair<Rule>,
) -> PropertyAndLabels<'a, Commit> {
    fn wrap_fn<'a, O>(
        f: impl Fn(&Commit) -> O + 'a,
    ) -> Box<dyn TemplateProperty<Commit, Output = O> + 'a> {
        Box::new(TemplatePropertyFn(f))
    }
    assert_eq!(pair.as_rule(), Rule::identifier);
    let property = match pair.as_str() {
        "description" => Property::String(wrap_fn(|commit| {
            cli_util::complete_newline(commit.description())
        })),
        "change_id" => Property::CommitOrChangeId(wrap_fn(move |commit| {
            CommitOrChangeId::new(repo, commit.change_id())
        })),
        "commit_id" => Property::CommitOrChangeId(wrap_fn(move |commit| {
            CommitOrChangeId::new(repo, commit.id())
        })),
        "author" => Property::Signature(wrap_fn(|commit| commit.author().clone())),
        "committer" => Property::Signature(wrap_fn(|commit| commit.committer().clone())),
        "working_copies" => Property::String(Box::new(WorkingCopiesProperty { repo })),
        "current_working_copy" => Property::Boolean(Box::new(IsWorkingCopyProperty {
            repo,
            workspace_id: workspace_id.clone(),
        })),
        "branches" => Property::String(Box::new(BranchProperty { repo })),
        "tags" => Property::String(Box::new(TagProperty { repo })),
        "git_refs" => Property::String(Box::new(GitRefsProperty { repo })),
        "git_head" => Property::String(Box::new(GitHeadProperty::new(repo))),
        "divergent" => Property::Boolean(wrap_fn(move |commit| {
            // The given commit could be hidden in e.g. obslog.
            let maybe_entries = repo.resolve_change_id(commit.change_id());
            maybe_entries.map_or(0, |entries| entries.len()) > 1
        })),
        "conflict" => Property::Boolean(wrap_fn(|commit| commit.tree().has_conflict())),
        "empty" => Property::Boolean(wrap_fn(move |commit| {
            commit.tree().id() == rewrite::merge_commit_trees(repo, &commit.parents()).id()
        })),
        name => panic!("unexpected identifier: {name}"),
    };
    PropertyAndLabels(property, vec![pair.as_str().to_string()])
}

fn parse_commit_term<'a>(
    repo: RepoRef<'a>,
    workspace_id: &WorkspaceId,
    pair: Pair<Rule>,
) -> Expression<'a, Commit> {
    assert_eq!(pair.as_rule(), Rule::term);
    let mut inner = pair.into_inner();
    let expr = inner.next().unwrap();
    let maybe_method = inner.next().unwrap();
    assert!(inner.next().is_none());
    match expr.as_rule() {
        Rule::literal => {
            let text = parse_string_literal(expr);
            let term = PropertyAndLabels(Property::String(Box::new(Literal(text))), vec![]);
            Expression::Property(parse_method_chain(maybe_method, term))
        }
        Rule::identifier => {
            let term = parse_commit_keyword(repo, workspace_id, expr);
            Expression::Property(parse_method_chain(maybe_method, term))
        }
        Rule::function => {
            let (name, mut args) = {
                let mut inner = expr.into_inner();
                let name = inner.next().unwrap();
                let args_pair = inner.next().unwrap();
                assert_eq!(name.as_rule(), Rule::identifier);
                assert_eq!(args_pair.as_rule(), Rule::function_arguments);
                (name, args_pair.into_inner())
            };
            match name.as_str() {
                "label" => {
                    let label_pair = args.next().unwrap();
                    let label_property = parse_commit_template_rule(repo, workspace_id, label_pair)
                        .into_plain_text();
                    let arg_template = match args.next() {
                        None => panic!("label() requires two arguments"),
                        Some(pair) => pair,
                    };
                    if args.next().is_some() {
                        panic!("label() accepts only two arguments")
                    }
                    let content = parse_commit_template_rule(repo, workspace_id, arg_template)
                        .into_template();
                    let labels = TemplateFunction::new(label_property, |s| {
                        s.split_whitespace().map(ToString::to_string).collect()
                    });
                    let template = Box::new(LabelTemplate::new(content, labels));
                    Expression::Template(template)
                }
                "if" => {
                    let condition_pair = args.next().unwrap();
                    let condition =
                        parse_commit_template_rule(repo, workspace_id, condition_pair.clone())
                            .try_into_boolean()
                            .unwrap_or_else(|| {
                                panic!("cannot yet use this as boolean: {condition_pair:?}")
                            });

                    let true_template = match args.next() {
                        None => panic!("if() requires at least two arguments"),
                        Some(pair) => {
                            parse_commit_template_rule(repo, workspace_id, pair).into_template()
                        }
                    };
                    let false_template = args.next().map(|pair| {
                        parse_commit_template_rule(repo, workspace_id, pair).into_template()
                    });
                    if args.next().is_some() {
                        panic!("if() accepts at most three arguments")
                    }
                    let template = Box::new(ConditionalTemplate::new(
                        condition,
                        true_template,
                        false_template,
                    ));
                    Expression::Template(template)
                }
                name => panic!("function {name} not implemented"),
            }
        }
        Rule::template => parse_commit_template_rule(repo, workspace_id, expr),
        other => panic!("unexpected term: {other:?}"),
    }
}

fn parse_commit_template_rule<'a>(
    repo: RepoRef<'a>,
    workspace_id: &WorkspaceId,
    pair: Pair<Rule>,
) -> Expression<'a, Commit> {
    assert_eq!(pair.as_rule(), Rule::template);
    let inner = pair.into_inner();
    let mut expressions = inner
        .map(|term| parse_commit_term(repo, workspace_id, term))
        .collect_vec();
    if expressions.len() == 1 {
        expressions.pop().unwrap()
    } else {
        let templates = expressions.into_iter().map(|x| x.into_template()).collect();
        Expression::Template(Box::new(ListTemplate(templates)))
    }
}

pub fn parse_commit_template<'a>(
    repo: RepoRef<'a>,
    workspace_id: &WorkspaceId,
    template_text: &str,
) -> Box<dyn Template<Commit> + 'a> {
    let mut pairs: Pairs<Rule> = TemplateParser::parse(Rule::program, template_text).unwrap();
    let first_pair = pairs.next().unwrap();
    if first_pair.as_rule() == Rule::EOI {
        Box::new(Literal(String::new()))
    } else {
        parse_commit_template_rule(repo, workspace_id, first_pair).into_template()
    }
}