import Foundation
#if os(macOS)
import AppKit
#else
import UIKit
#endif

@MainActor extension DocsTextView {
    private var ruleContent: NSAttributedString {
        #if os(macOS)
        attributedString()
        #else
        attributedText
        #endif
    }
    var ruleCaret: Int { ruleSelection.location }
    private var ruleSelection: NSRange {
        #if os(macOS)
        selectedRange()
        #else
        selectedRange
        #endif
    }
    private func replaceRule(_ range: NSRange, with value: NSAttributedString) {
        #if os(macOS)
        textStorage?.replaceCharacters(in: range, with: value)
        setSelectedRange(NSRange(location: range.location + value.length, length: 0))
        didChangeText()
        #else
        textStorage.replaceCharacters(in: range, with: value)
        selectedRange = NSRange(location: range.location + value.length, length: 0)
        delegate?.textViewDidChange?(self)
        #endif
    }
    func interceptInput(_ text: String, range: NSRange) -> Bool {
        guard isEditable else { return true }
        if text.isEmpty, lastInputRule != nil, revertInputRule() { return true }
        lastInputRule = nil
        if let plan = DocumentInputRules.plan(in: ruleContent, range: range, replacement: text) {
            let command: [String: JSONValue] = ["op": .string("display_autoformat"), "at": .number(Double(plan.paragraphLocation)), "length": .number(Double(plan.removeLength)), "kind": .string(plan.kind), "level": .number(Double(plan.level))]
            guard ruleCommand?(command) == true else { return true }
            replaceRule(NSRange(location: plan.paragraphLocation, length: plan.removeLength), with: NSAttributedString(string: ""))
            let style = (plan.priorParagraphStyle.mutableCopy() as? NSMutableParagraphStyle) ?? NSMutableParagraphStyle()
            if plan.kind == "bullet_list" || plan.kind == "ordered_list" {
                style.textLists = [NSTextList(markerFormat: plan.kind == "bullet_list" ? .disc : .decimal, options: 0)]
            }
            let paragraph = (ruleContent.string as NSString).paragraphRange(for: NSRange(location: min(plan.paragraphLocation, max(0, ruleContent.length - 1)), length: 0))
            let attributes: [NSAttributedString.Key: Any] = [.paragraphStyle: style, .docsBlockType: plan.kind == "heading" ? "heading" : "paragraph", .docsHeading: plan.level]
            #if os(macOS)
            textStorage?.addAttributes(attributes, range: paragraph)
            #else
            textStorage.addAttributes(attributes, range: paragraph)
            #endif
            lastInputRule = plan
            return true
        }
        if text == "\n", range.length == 0, ruleContent.length > 0 {
            let raw = ruleContent.string as NSString
            let paragraph = raw.paragraphRange(for: NSRange(location: min(range.location, raw.length - 1), length: 0))
            let value = raw.substring(with: paragraph)
            let style = ruleContent.attribute(.paragraphStyle, at: min(range.location, raw.length - 1), effectiveRange: nil) as? NSParagraphStyle
            if value == "\n", style?.textLists.isEmpty == false {
                guard ruleCommand?(["op": .string("display_exit_list"), "at": .number(Double(range.location)), "kind": .string("paragraph")]) == true else { return true }
                let plain = (style?.mutableCopy() as? NSMutableParagraphStyle) ?? NSMutableParagraphStyle()
                plain.textLists = []; plain.headIndent = 0; plain.firstLineHeadIndent = 0
                replaceRule(paragraph, with: NSAttributedString(string: "\n", attributes: [.paragraphStyle: plain]))
                #if os(macOS)
                setSelectedRange(range)
                #else
                selectedRange = range
                #endif
                return true
            }
        }
        return false
    }
    func revertInputRule() -> Bool {
        guard !isComposing, isEditable, let plan = lastInputRule,
              ruleSelection == NSRange(location: plan.paragraphLocation, length: 0) else { lastInputRule = nil; return false }
        let command: [String: JSONValue] = ["op": .string("display_revert_rule"), "at": .number(Double(plan.paragraphLocation)), "kind": .string(plan.kind), "prior_type": .string(plan.priorBlockType), "prior_attrs": .object(plan.priorAttrs.mapValues(JSONValue.string)), "text": .string(plan.prefix)]
        guard ruleCommand?(command) == true else { return true }
        replaceRule(NSRange(location: plan.paragraphLocation, length: 0), with: NSAttributedString(string: plan.prefix, attributes: [.paragraphStyle: plan.priorParagraphStyle, .docsBlockType: plan.priorBlockType]))
        let paragraph = (ruleContent.string as NSString).paragraphRange(for: NSRange(location: plan.paragraphLocation, length: 0))
        let restored: [NSAttributedString.Key: Any] = [.paragraphStyle: plan.priorParagraphStyle, .docsBlockType: plan.priorBlockType, .docsBlockAttributes: (try? JSONEncoder().encode(plan.priorAttrs)) ?? Data()]
        #if os(macOS)
        textStorage?.addAttributes(restored, range: paragraph)
        #else
        textStorage.addAttributes(restored, range: paragraph)
        #endif
        lastInputRule = nil
        return true
    }
}