//! ref: composer/vendor/composer/pcre/src/Preg.php
//!
//! The following two exception classes are intentionally not ported:
//!
//! - `PcreException`: thrown when a `preg_*()` call returns false. Composer never feeds a pattern
//!   that fails to compile at runtime, so such a failure would be a programming error rather than
//!   a recoverable condition; they panic instead.
//! - `UnexpectedNullMatchException`: thrown by the `Preg::*StrictGroups()` variants when a capture
//!   group did not participate. Those variants were dropped because Rust's `Option` already
//!   distinguishes participating from non-participating groups.
//!
//! See docs/dev/regex-porting.md for more detailed regex porting rules.

use indexmap::IndexMap;
use shirabe_php_shim::{
    PREG_OFFSET_CAPTURE, PREG_SET_ORDER, PREG_SPLIT_OFFSET_CAPTURE, PREG_UNMATCHED_AS_NULL,
};

pub use shirabe_php_shim::CaptureKey;

#[derive(Debug)]
pub struct Preg;

impl Preg {
    pub fn match3(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, String>>,
    ) -> bool {
        Self::match5(pattern, subject, matches, 0, 0)
    }

    pub fn match5(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, String>>,
        flags: i64,
        offset: usize,
    ) -> bool {
        Self::check_offset_capture(flags, "matchWithOffsets");

        let mut internal: IndexMap<CaptureKey, Option<String>> = IndexMap::new();
        let result = shirabe_php_shim::preg_match2(
            pattern,
            subject,
            &mut internal,
            flags | PREG_UNMATCHED_AS_NULL,
            offset,
        );

        if let Some(out) = matches {
            *out = drop_null_matches(internal);
        }

        result
    }

    pub fn match_all(pattern: &str, subject: &str) -> usize {
        Self::match_all5(pattern, subject, None, 0, 0)
    }

    pub fn match_all3(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, Vec<String>>>,
    ) -> usize {
        Self::match_all5(pattern, subject, matches, 0, 0)
    }

    pub fn match_all5(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, Vec<String>>>,
        flags: i64,
        offset: usize,
    ) -> usize {
        Self::check_offset_capture(flags, "matchAllWithOffsets");
        Self::check_set_order(flags);

        let mut internal: IndexMap<CaptureKey, Vec<Option<String>>> = IndexMap::new();
        let result = shirabe_php_shim::preg_match_all2(
            pattern,
            subject,
            &mut internal,
            flags | PREG_UNMATCHED_AS_NULL,
            offset,
        );

        if let Some(out) = matches {
            *out = null_to_empty_match_all(internal);
        }

        result
    }

    pub fn match_all_with_offsets5(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, Vec<(String, usize)>>>,
        flags: i64,
        offset: usize,
    ) -> usize {
        Self::check_set_order(flags);

        let mut internal: IndexMap<CaptureKey, Vec<(Option<String>, i64)>> = IndexMap::new();
        let result = shirabe_php_shim::preg_match_all_offset_capture2(
            pattern,
            subject,
            &mut internal,
            flags | PREG_UNMATCHED_AS_NULL | PREG_OFFSET_CAPTURE,
            offset,
        );

        if let Some(out) = matches {
            *out = null_to_empty_offset_match_all(internal);
        }

        result
    }

    pub fn replace(pattern: &str, replacement: &str, subject: &str) -> String {
        Self::replace_impl(pattern, replacement, subject, -1, None)
    }

    pub fn replace4(pattern: &str, replacement: &str, subject: &str, limit: i64) -> String {
        Self::replace_impl(pattern, replacement, subject, limit, None)
    }

    pub fn replace5(
        pattern: &str,
        replacement: &str,
        subject: &str,
        limit: i64,
        count: &mut usize,
    ) -> String {
        Self::replace_impl(pattern, replacement, subject, limit, Some(count))
    }

    fn replace_impl(
        pattern: &str,
        replacement: &str,
        subject: &str,
        limit: i64,
        count: Option<&mut usize>,
    ) -> String {
        // `$subject` is statically a string here, so the is_scalar/is_array
        // guards (ARRAY_MSG / INVALID_TYPE_MSG) of the PHP original are
        // unreachable and not reproduced.
        shirabe_php_shim::preg_replace2(pattern, replacement, subject, limit, count)
    }

    pub fn replace_callback<F: FnMut(&IndexMap<CaptureKey, String>) -> String>(
        pattern: &str,
        replacement: F,
        subject: &str,
    ) -> String {
        Self::replace_callback6(pattern, replacement, subject, -1, None, 0)
    }

    pub fn replace_callback6<F: FnMut(&IndexMap<CaptureKey, String>) -> String>(
        pattern: &str,
        mut replacement: F,
        subject: &str,
        limit: i64,
        count: Option<&mut usize>,
        flags: i64,
    ) -> String {
        let adapter = |internal: &IndexMap<CaptureKey, Option<String>>| -> String {
            replacement(&drop_null_matches_ref(internal))
        };

        shirabe_php_shim::preg_replace_callback2(pattern, adapter, subject, limit, count, flags)
    }

    pub fn split(pattern: &str, subject: &str) -> Vec<String> {
        Self::split4(pattern, subject, -1, 0)
    }

    pub fn split4(pattern: &str, subject: &str, limit: i64, flags: i64) -> Vec<String> {
        assert!(
            flags & PREG_SPLIT_OFFSET_CAPTURE == 0,
            "PREG_SPLIT_OFFSET_CAPTURE is not supported as it changes the type of $matches, use splitWithOffsets() instead"
        );

        shirabe_php_shim::preg_split2(pattern, subject, limit, flags)
    }

    pub fn grep(pattern: &str, array: &[&str]) -> Vec<String> {
        Self::grep3(pattern, array, 0)
    }

    pub fn grep3(pattern: &str, array: &[&str], flags: i64) -> Vec<String> {
        shirabe_php_shim::preg_grep2(pattern, array, flags)
    }

    pub fn is_match(pattern: &str, subject: &str) -> bool {
        Self::match5(pattern, subject, None, 0, 0)
    }

    pub fn is_match3(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, String>>,
    ) -> bool {
        Self::match5(pattern, subject, matches, 0, 0)
    }

    pub fn is_match5(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, String>>,
        flags: i64,
        offset: usize,
    ) -> bool {
        Self::match5(pattern, subject, matches, flags, offset)
    }

    pub fn is_match_named(
        pattern: &str,
        subject: &str,
        matches: &mut IndexMap<String, String>,
    ) -> bool {
        let mut internal: IndexMap<CaptureKey, Option<String>> = IndexMap::new();
        let result = shirabe_php_shim::preg_match2(
            pattern,
            subject,
            &mut internal,
            PREG_UNMATCHED_AS_NULL,
            0,
        );

        matches.clear();
        for (key, value) in internal {
            if let (CaptureKey::ByName(name), Some(value)) = (key, value) {
                matches.insert(name, value);
            }
        }

        result
    }

    pub fn is_match_with_indexed_captures(pattern: &str, subject: &str) -> Option<Vec<String>> {
        // Classic preg_match semantics (no PREG_UNMATCHED_AS_NULL): trailing
        // unmatched groups are truncated, interior unmatched groups become "".
        let mut internal: IndexMap<CaptureKey, Option<String>> = IndexMap::new();
        let result = shirabe_php_shim::preg_match2(pattern, subject, &mut internal, 0, 0);

        if !result {
            return None;
        }

        let max_index = internal
            .keys()
            .filter_map(|key| match key {
                CaptureKey::ByIndex(index) => Some(*index),
                CaptureKey::ByName(_) => None,
            })
            .max()
            .unwrap_or(0);

        let mut captures = Vec::with_capacity(max_index + 1);
        for index in 0..=max_index {
            let value = internal
                .get(&CaptureKey::ByIndex(index))
                .and_then(|value| value.clone())
                .unwrap_or_default();
            captures.push(value);
        }

        Some(captures)
    }

    pub fn is_match_all3(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, Vec<String>>>,
    ) -> bool {
        Self::match_all5(pattern, subject, matches, 0, 0) > 0
    }

    pub fn is_match_all_with_offsets3(
        pattern: &str,
        subject: &str,
        matches: Option<&mut IndexMap<CaptureKey, Vec<(String, usize)>>>,
    ) -> bool {
        Self::match_all_with_offsets5(pattern, subject, matches, 0, 0) > 0
    }

    fn check_offset_capture(flags: i64, use_function_name: &str) {
        assert!(
            flags & PREG_OFFSET_CAPTURE == 0,
            "PREG_OFFSET_CAPTURE is not supported as it changes the type of $matches, use {}() instead",
            use_function_name
        );
    }

    fn check_set_order(flags: i64) {
        assert!(
            flags & PREG_SET_ORDER == 0,
            "PREG_SET_ORDER is not supported as it changes the type of $matches"
        );
    }
}

// Drops `null` (unmatched) groups, mirroring how the public `string`-valued
// `matches` map represents PHP's `string|null` entries by their absence.
fn drop_null_matches(
    matches: IndexMap<CaptureKey, Option<String>>,
) -> IndexMap<CaptureKey, String> {
    matches
        .into_iter()
        .filter_map(|(key, value)| value.map(|value| (key, value)))
        .collect()
}

fn drop_null_matches_ref(
    matches: &IndexMap<CaptureKey, Option<String>>,
) -> IndexMap<CaptureKey, String> {
    matches
        .iter()
        .filter_map(|(key, value)| value.clone().map(|value| (key.clone(), value)))
        .collect()
}

// In the `Vec<String>`-valued maps a per-iteration `null` cannot be stored, so
// unmatched groups collapse to "" (the classic non-PREG_UNMATCHED_AS_NULL form).
fn null_to_empty_match_all(
    matches: IndexMap<CaptureKey, Vec<Option<String>>>,
) -> IndexMap<CaptureKey, Vec<String>> {
    matches
        .into_iter()
        .map(|(key, values)| {
            (
                key,
                values
                    .into_iter()
                    .map(|value| value.unwrap_or_default())
                    .collect(),
            )
        })
        .collect()
}

fn null_to_empty_offset_match_all(
    matches: IndexMap<CaptureKey, Vec<(Option<String>, i64)>>,
) -> IndexMap<CaptureKey, Vec<(String, usize)>> {
    matches
        .into_iter()
        .map(|(key, values)| {
            (
                key,
                values
                    .into_iter()
                    .map(|(value, offset)| (value.unwrap_or_default(), offset.max(0) as usize))
                    .collect(),
            )
        })
        .collect()
}