// See: - https://docs.ruby-lang.org/en/3.4/syntax/literals_rdoc.html#label-Percent+Literals
//      - https://docs.ruby-lang.org/en/3.4/syntax/literals_rdoc.html#label-25w+and+-25W-3A+String-Array+Literals
use crate::cursor;
use crate::extractor::bracket_stack;
use crate::extractor::pre_processors::pre_processor::PreProcessor;
use crate::scanner::pre_process_input;
use bstr::ByteVec;
use regex::{Regex, RegexBuilder};
use std::sync;

static TEMPLATE_START_REGEX: sync::LazyLock<Regex> = sync::LazyLock::new(|| {
    RegexBuilder::new(r#"\s*([a-z0-9_-]+)_template\s*<<[-~]?([A-Z]+)$"#)
        .multi_line(true)
        .build()
        .unwrap()
});

static TEMPLATE_END_REGEX: sync::LazyLock<Regex> = sync::LazyLock::new(|| {
    RegexBuilder::new(r#"^\s*([A-Z]+)"#)
        .multi_line(true)
        .build()
        .unwrap()
});

#[derive(Debug, Default)]
pub struct Ruby;

impl PreProcessor for Ruby {
    fn process(&self, content: &[u8]) -> Vec<u8> {
        let len = content.len();
        let mut result = content.to_vec();
        let mut cursor = cursor::Cursor::new(content);
        let mut bracket_stack = bracket_stack::BracketStack::default();

        // Extract embedded template languages
        // https://viewcomponent.org/guide/templates.html#interpolations
        // Only process if content is valid UTF-8, otherwise skip HEREDOC extraction
        // but still perform the byte-level Ruby processing below
        if let Ok(content_as_str) = std::str::from_utf8(content) {
            let starts = TEMPLATE_START_REGEX
                .captures_iter(content_as_str)
                .collect::<Vec<_>>();
            let ends = TEMPLATE_END_REGEX
                .captures_iter(content_as_str)
                .collect::<Vec<_>>();

            for start in starts.iter() {
                // The language for this block
                let lang = start.get(1).unwrap().as_str();

                // The HEREDOC delimiter
                let delimiter_start = start.get(2).unwrap().as_str();

                // Where the "body" starts for the HEREDOC block
                let body_start = start.get(0).unwrap().end();

                // Look through all of the ends to find a matching language
                for end in ends.iter() {
                    // 1. This must appear after the start
                    let body_end = end.get(0).unwrap().start();
                    if body_end < body_start {
                        continue;
                    }

                    // The languages must match otherwise we haven't found the end
                    let delimiter_end = end.get(1).unwrap().as_str();
                    if delimiter_end != delimiter_start {
                        continue;
                    }

                    let body = &content_as_str[body_start..body_end];
                    let replaced =
                        pre_process_input(body.as_bytes().to_vec(), &lang.to_ascii_lowercase());

                    result.replace_range(body_start..body_end, replaced);
                    break;
                }
            }
        }

        // Ruby extraction
        while cursor.pos < len {
            match cursor.curr() {
                b'"' => {
                    cursor.advance();

                    while cursor.pos < len {
                        match cursor.curr() {
                            // Escaped character, skip ahead to the next character
                            b'\\' => cursor.advance_twice(),

                            // End of the string
                            b'"' => break,

                            // Everything else is valid
                            _ => cursor.advance(),
                        };
                    }

                    cursor.advance();
                    continue;
                }

                b'\'' => {
                    cursor.advance();

                    while cursor.pos < len {
                        match cursor.curr() {
                            // Escaped character, skip ahead to the next character
                            b'\\' => cursor.advance_twice(),

                            // End of the string
                            b'\'' => break,

                            // Everything else is valid
                            _ => cursor.advance(),
                        };
                    }

                    cursor.advance();
                    continue;
                }

                // Replace comments in Ruby files
                //
                // Except for strict locals, these are defined in a `<%# locals: … %>`. Checking if
                // the comment is preceded by a `%` should be enough without having to perform more
                // parsing logic. Worst case we _do_ scan a few comments.
                //
                // We also want to skip interpolation syntax, which look like `#{…}`.
                b'#' if !matches!(cursor.prev(), b'%') && !matches!(cursor.next(), b'{') => {
                    result[cursor.pos] = b' ';
                    cursor.advance();

                    while cursor.pos < len {
                        match cursor.curr() {
                            // End of the comment
                            b'\n' => break,

                            // Everything else is part of the comment and replaced
                            _ => {
                                result[cursor.pos] = b' ';
                                cursor.advance();
                            }
                        };
                    }

                    cursor.advance();
                    continue;
                }

                _ => {}
            }

            // Looking for `%w`, `%W`, or `%p`
            if cursor.curr() != b'%' || !matches!(cursor.next(), b'w' | b'W' | b'p') {
                cursor.advance();
                continue;
            }

            // A `%` that follows a value is a modulo operation, not a percent literal. E.g.: the
            // `50%w` in `hit rate 50%w.`
            if cursor.prev().is_ascii_alphanumeric()
                || matches!(cursor.prev(), b'_' | b')' | b']' | b'}')
            {
                cursor.advance();
                continue;
            }

            cursor.advance_twice();

            // Boundary character
            let boundary = match cursor.curr() {
                b'[' => b']',
                b'(' => b')',
                b'{' => b'}',
                b'<' => b'>',
                b' ' => b'\n',

                // Any other ASCII punctuation can be used as a custom delimiter
                c if c.is_ascii_punctuation() => c,

                // Everything else is not a valid delimiter
                _ => {
                    cursor.advance();
                    continue;
                }
            };

            bracket_stack.reset();

            // Replace the current character with a space
            result[cursor.pos] = b' ';

            // Skip the boundary character
            cursor.advance();

            while cursor.pos < len {
                match cursor.curr() {
                    // Skip escaped characters, unless the backslash is the delimiter itself
                    b'\\' if boundary != b'\\' => {
                        // Use backslash to embed spaces in the strings.
                        if cursor.next() == b' ' {
                            result[cursor.pos] = b' ';
                        }

                        cursor.advance();
                    }

                    // Start of a nested bracket
                    b'[' | b'(' | b'{' => {
                        bracket_stack.push(cursor.curr());
                    }

                    // Start of a nested `<…>`, which Ruby allows inside a `%w<…>` literal
                    b'<' if boundary == b'>' => {
                        bracket_stack.push(cursor.curr());
                    }

                    // End of a nested bracket
                    b']' | b')' | b'}' if !bracket_stack.is_empty() => {
                        if !bracket_stack.pop(cursor.curr()) {
                            // Unbalanced
                            cursor.advance();
                        }
                    }

                    // End of a nested `<…>`
                    b'>' if boundary == b'>' && !bracket_stack.is_empty() => {
                        if !bracket_stack.pop(cursor.curr()) {
                            // Unbalanced
                            cursor.advance();
                        }
                    }

                    // End of the pattern, replace the boundary character with a space
                    _ if cursor.curr() == boundary => {
                        if boundary != b'\n' {
                            result[cursor.pos] = b' ';
                        }

                        break;
                    }

                    // Everything else is valid
                    _ => {}
                }

                cursor.advance();
            }
        }

        result
    }
}

#[cfg(test)]
mod tests {
    use super::Ruby;
    use crate::extractor::pre_processors::pre_processor::PreProcessor;

    #[test]
    fn test_ruby_pre_processor() {
        for (input, expected) in [
            // %w[…]
            ("%w[flex px-2.5]", "%w flex px-2.5 "),
            (
                "%w[flex data-[state=pending]:bg-[#0088cc] flex-col]",
                "%w flex data-[state=pending]:bg-[#0088cc] flex-col ",
            ),
            // %w{…}
            ("%w{flex px-2.5}", "%w flex px-2.5 "),
            (
                "%w{flex data-[state=pending]:bg-(--my-color) flex-col}",
                "%w flex data-[state=pending]:bg-(--my-color) flex-col ",
            ),
            // %w(…)
            ("%w(flex px-2.5)", "%w flex px-2.5 "),
            (
                "%w(flex data-[state=pending]:bg-(--my-color) flex-col)",
                "%w flex data-[state=pending]:bg-(--my-color) flex-col ",
            ),
            // %w<…>
            ("%w<flex px-2.5>", "%w flex px-2.5 "),
            (
                "%w<flex data-[state=pending]:bg-(--my-color) flex-col>",
                "%w flex data-[state=pending]:bg-(--my-color) flex-col ",
            ),
            // Nested `<…>` does not end the literal
            ("%w<flex <nested> px-2.5>", "%w flex <nested> px-2.5 "),
            // %w|…|, %w:…:, %w!…!
            ("%w|flex px-2.5|", "%w flex px-2.5 "),
            ("%w:flex px-2.5:", "%w flex px-2.5 "),
            ("%w!flex px-2.5!", "%w flex px-2.5 "),
            (r#"%w\flex px-2.5\"#, r#"%w flex px-2.5 "#),
            // A `%` that follows a value is a modulo operation, not a percent literal
            (
                "hit rate 50%w.\n%w[flex px-2.5]",
                "hit rate 50%w.\n%w flex px-2.5 ",
            ),

            // %w …\n
            ("%w flex px-2.5\n", "%w flex px-2.5\n"),

            // Use backslash to embed spaces in the strings.
            (r#"%w[foo\ bar baz\ bat]"#, r#"%w foo  bar baz  bat "#),
            (r#"%W[foo\ bar baz\ bat]"#, r#"%W foo  bar baz  bat "#),

            // The nested delimiters evaluated to a flat array of strings
            // (not nested array).
            (r#"%w[foo[bar baz]qux]"#, r#"%w foo[bar baz]qux "#),

            (
              "# test\n# test\n# {ActiveRecord::Base#save!}[rdoc-ref:Persistence#save!]\n%w[flex px-2.5]",
              "      \n      \n                                                        \n%w flex px-2.5 "
            ),

            (r#""foo # bar""#, r#""foo # bar""#),
            (r#"'foo # bar'"#, r#"'foo # bar'"#),
            (
              r#"def call = tag.span "Foo", class: %w[rounded-full h-0.75 w-0.75]"#,
              r#"def call = tag.span "Foo", class: %w rounded-full h-0.75 w-0.75 "#
            ),

            (r#"%w[foo ' bar]"#, r#"%w foo ' bar "#),
            (r#"%w[foo " bar]"#, r#"%w foo " bar "#),
            (r#"%W[foo ' bar]"#, r#"%W foo ' bar "#),
            (r#"%W[foo " bar]"#, r#"%W foo " bar "#),

            (r#"%p foo ' bar "#, r#"%p foo ' bar "#),
            (r#"%p foo " bar "#, r#"%p foo " bar "#),

            (
              "%p has a ' quote\n# this should be removed\n%p has a ' quote",
              "%p has a ' quote\n                        \n%p has a ' quote"
            ),
            (
              "%p has a \" quote\n# this should be removed\n%p has a \" quote",
              "%p has a \" quote\n                        \n%p has a \" quote"
            ),

            (
              "%w#this text is kept# # this text is not",
              "%w this text is kept                    ",
            ),
        ] {
            Ruby::test(input, expected);
        }
    }

    #[test]
    fn test_ruby_extraction() {
        for (input, expected) in [
            // %w[…]
            ("%w[flex px-2.5]", vec!["flex", "px-2.5"]),
            ("%w[px-2.5 flex]", vec!["flex", "px-2.5"]),
            ("%w[2xl:flex]", vec!["2xl:flex"]),
            (
                "%w[flex data-[state=pending]:bg-[#0088cc] flex-col]",
                vec!["flex", "data-[state=pending]:bg-[#0088cc]", "flex-col"],
            ),
            // %w{…}
            ("%w{flex px-2.5}", vec!["flex", "px-2.5"]),
            ("%w{px-2.5 flex}", vec!["flex", "px-2.5"]),
            ("%w{2xl:flex}", vec!["2xl:flex"]),
            (
                "%w{flex data-[state=pending]:bg-(--my-color) flex-col}",
                vec!["flex", "data-[state=pending]:bg-(--my-color)", "flex-col"],
            ),
            // %w(…)
            ("%w(flex px-2.5)", vec!["flex", "px-2.5"]),
            ("%w(px-2.5 flex)", vec!["flex", "px-2.5"]),
            ("%w(2xl:flex)", vec!["2xl:flex"]),
            (
                "%w(flex data-[state=pending]:bg-(--my-color) flex-col)",
                vec!["flex", "data-[state=pending]:bg-(--my-color)", "flex-col"],
            ),
            // %w<…>
            ("%w<flex px-2.5>", vec!["flex", "px-2.5"]),
            ("%w<px-2.5 flex>", vec!["flex", "px-2.5"]),
            ("%w<2xl:flex>", vec!["2xl:flex"]),
            (
                "%w<flex data-[state=pending]:bg-(--my-color) flex-col>",
                vec!["flex", "data-[state=pending]:bg-(--my-color)", "flex-col"],
            ),
            // Nested `<…>` does not end the literal
            ("%w<flex <nested> px-2.5>", vec!["flex", "px-2.5"]),
            // %w|…|, %w:…:, %w!…!
            ("%w|flex px-2.5|", vec!["flex", "px-2.5"]),
            ("%w:flex px-2.5:", vec!["flex", "px-2.5"]),
            ("%w!flex px-2.5!", vec!["flex", "px-2.5"]),

            (
              "# test\n# test\n# {ActiveRecord::Base#save!}[rdoc-ref:Persistence#save!]\n%w[flex px-2.5]",
              vec!["flex", "px-2.5"],
            ),

            (r#""foo # bar""#, vec!["foo", "bar"]),
            (r#"'foo # bar'"#, vec!["foo", "bar"]),

            (r#"%w[foo ' bar]"#, vec!["foo", "bar"]),
        ] {
            Ruby::test_extract_contains(input, expected);
        }
    }

    // https://github.com/tailwindlabs/tailwindcss/issues/17334
    #[test]
    fn test_embedded_slim_extraction() {
        let input = r#"
            class QweComponent < ApplicationComponent
              slim_template <<~SLIM
                button.rounded-full.bg-red-500
                  | Some text
                button.rounded-full(
                  class="flex"
                )
                  | Some text
              SLIM
            end
        "#;

        Ruby::test_extract_contains(input, vec!["rounded-full", "bg-red-500", "flex"]);

        // Embedded Svelte just to verify that we properly pick up the `{x}_template`
        let input = r#"
            class QweComponent < ApplicationComponent
              svelte_template <<~HTML
                  <div class:flex="true"></div>
              HTML
            end
        "#;

        Ruby::test_extract_contains(input, vec!["flex"]);

        // Together in the same file
        let input = r#"
            class QweComponent < ApplicationComponent
              slim_template <<~SLIM
                button.z-1.z-2
                  | Some text
              SLIM
            end

            class QweComponent < ApplicationComponent
              svelte_template <<~HTML
                <div class:z-3="true"></div>
              HTML
            end
        "#;
        Ruby::test_extract_contains(input, vec!["z-1", "z-2", "z-3"]);
    }

    // https://github.com/tailwindlabs/tailwindcss/issues/19728
    #[test]
    fn test_interpolated_expressions() {
        let input = r#"
            def width_class(width = nil)
              <<~STYLE_CLASS
                #{width || 'w-100'}
              STYLE_CLASS
            end
        "#;

        Ruby::test_extract_contains(input, vec!["w-100"]);
    }

    // https://github.com/tailwindlabs/tailwindcss/issues/19239
    #[test]
    fn test_skip_comments() {
        let input = r#"
          # From activerecord-8.1.1/lib/active_record/errors.rb:147
          # Rails uses RDoc cross-reference syntax in inline documentation:
          # {ActiveRecord::Base#save!}[rdoc-ref:Persistence#save!]
        "#;

        // Nothing should be extracted from comments, so expect an empty array.
        Ruby::test_extract_exact(input, vec![]);
    }

    // https://github.com/tailwindlabs/tailwindcss/issues/19481
    #[test]
    fn test_strict_locals() {
        // Strict locals are defined in a `<%# locals: … %>`, but the `#` looks like a comment
        // which we should not ignore in this case.
        let input = r#"
          <%# locals: (css: "text-amber-600") %>
          <% more_css = "text-sky-500" %>

          <p class="text-green-500">
            In a partial
          </p>

          <p class="<%= css %>">
            In a partial using explicit local variables
          </p>

          <p class="<%= more_css %>">
            In a partial using explicit local variables
          </p>
        "#;

        Ruby::test_extract_contains(
            input,
            vec!["text-amber-600", "text-sky-500", "text-green-500"],
        );
    }

    #[test]
    fn test_invalid_utf8_does_not_panic() {
        // Invalid UTF-8 sequence: 0x80 is a continuation byte without a leading byte
        let invalid_utf8: &[u8] = &[0x80, 0x81, 0x82];

        let processor = Ruby::default();

        // Should not panic, just return the input unchanged
        let result = processor.process(invalid_utf8);
        assert_eq!(result, invalid_utf8);
    }

    #[test]
    fn test_valid_utf8_with_multibyte_chars() {
        // Test that valid UTF-8 with multi-byte characters (like em-dashes) works
        let input = "# Comment with em—dash\n%w[flex px-2.5]";

        Ruby::test_extract_contains(input, vec!["flex", "px-2.5"]);
    }
}