//
//  Mentions.swift
//  damus
//
//  Created by William Casarin on 2022-05-04.
//

import Foundation

enum MentionType {
    case pubkey
    case event
    
    var ref: String {
        switch self {
        case .pubkey:
            return "p"
        case .event:
            return "e"
        }
    }
}

struct Mention {
    let index: Int
    let type: MentionType
    let ref: ReferencedId
}

struct IdBlock: Identifiable {
    let id: String = UUID().description
    let block: Block
}

struct Invoice {
    let description: String
    let amount: Int64
    let string: String
    let expiry: UInt64
    let payment_hash: Data
    let created_at: UInt64
}

enum Block {
    case text(String)
    case mention(Mention)
    case hashtag(String)
    case url(URL)
    case invoice(Invoice)
    
    var is_invoice: Invoice? {
        if case .invoice(let invoice) = self {
            return invoice
        }
        return nil
    }
    
    var is_hashtag: String? {
        if case .hashtag(let htag) = self {
            return htag
        }
        return nil
    }
    
    var is_url: URL? {
        if case .url(let url) = self {
            return url
        }
        
        return nil
    }
    
    var is_text: String? {
        if case .text(let txt) = self {
            return txt
        }
        return nil
    }
    
    var is_mention: Bool {
        if case .mention = self {
            return true
        }
        return false
    }
}

func render_blocks(blocks: [Block]) -> String {
    return blocks.reduce("") { str, block in
        switch block {
        case .mention(let m):
            return str + "#[\(m.index)]"
        case .text(let txt):
            return str + txt
        case .hashtag(let htag):
            return str + "#" + htag
        case .url(let url):
            return str + url.absoluteString
        case .invoice(let inv):
            return str + inv.string
        }
    }
}

func parse_textblock(str: String, from: Int, to: Int) -> Block {
    return .text(String(substring(str, start: from, end: to)))
}

func parse_mentions(content: String, tags: [[String]]) -> [Block] {
    var out: [Block] = []
    
    var bs = blocks()
    bs.num_blocks = 0;
    
    blocks_init(&bs)
    
    let bytes = content.utf8CString
    bytes.withUnsafeBufferPointer { p in
        damus_parse_content(&bs, p.baseAddress)
    }
    
    var i = 0
    while (i < bs.num_blocks) {
        let block = bs.blocks[i]
        
        if let converted = convert_block(block, tags: tags) {
            out.append(converted)
        }
        
        i += 1
    }
    
    blocks_free(&bs)
    
    return out
}

func strblock_to_string(_ s: str_block_t) -> String? {
    let len = s.end - s.start
    let bytes = Data(bytes: s.start, count: len)
    return String(bytes: bytes, encoding: .utf8)
}

func convert_block(_ b: block_t, tags: [[String]]) -> Block? {
    if b.type == BLOCK_HASHTAG {
        guard let str = strblock_to_string(b.block.str) else {
            return nil
        }
        return .hashtag(str)
    } else if b.type == BLOCK_TEXT {
        guard let str = strblock_to_string(b.block.str) else {
            return nil
        }
        return .text(str)
    } else if b.type == BLOCK_MENTION {
        return convert_mention_block(ind: b.block.mention, tags: tags)
    } else if b.type == BLOCK_URL {
        return convert_url_block(b.block.str)
    } else if b.type == BLOCK_INVOICE {
        return convert_invoice_block(b.block.invoice)
    }
    
    return nil
}

func convert_url_block(_ b: str_block) -> Block? {
    guard let str = strblock_to_string(b) else {
        return nil
    }
    guard let url = URL(string: str) else {
        return .text(str)
    }
    return .url(url)
}

func maybe_pointee<T>(_ p: UnsafeMutablePointer<T>!) -> T? {
    guard p != nil else {
        return nil
    }
    return p.pointee
}

func convert_invoice_block(_ b: invoice_block) -> Block? {
    guard let invstr = strblock_to_string(b.invstr) else {
        return nil
    }
    
    guard var b11 = maybe_pointee(b.bolt11) else {
        return nil
    }
    
    var description = ""
    if b11.description != nil {
        description = String(cString: b11.description)
    }
    
    guard let msat = maybe_pointee(b11.msat) else {
        return nil
    }
    let amount = Int64(msat.millisatoshis)
    let payment_hash = Data(bytes: &b11.payment_hash, count: 32)
    let hex = hex_encode(payment_hash)
    let created_at = b11.timestamp
    
    tal_free(b.bolt11)
    return .invoice(Invoice(description: description, amount: amount, string: invstr, expiry: b11.expiry, payment_hash: payment_hash, created_at: created_at))
}

func convert_mention_block(ind: Int32, tags: [[String]]) -> Block?
{
    let ind = Int(ind)
    
    if ind < 0 || (ind + 1 > tags.count) || tags[ind].count < 2 {
        return .text("#[\(ind)]")
    }
        
    let tag = tags[ind]
    guard let mention_type = parse_mention_type(tag[0]) else {
        return .text("#[\(ind)]")
    }
    
    guard let ref = tag_to_refid(tag) else {
        return .text("#[\(ind)]")
    }
    
    return .mention(Mention(index: ind, type: mention_type, ref: ref))
}

func parse_mentions_old(content: String, tags: [[String]]) -> [Block] {
    let p = Parser(pos: 0, str: content)
    var blocks: [Block] = []
    var starting_from: Int = 0
    
    while p.pos < content.count {
        if !consume_until(p, match: { !$0.isWhitespace}) {
            break
        }
        
        let pre_mention = p.pos
        
        let c = peek_char(p, 0)
        let pr = peek_char(p, -1)
        
        if c == "#" {
            if let mention = parse_mention(p, tags: tags) {
                blocks.append(parse_textblock(str: p.str, from: starting_from, to: pre_mention))
                blocks.append(.mention(mention))
                starting_from = p.pos
            } else if let hashtag = parse_hashtag(p) {
                blocks.append(parse_textblock(str: p.str, from: starting_from, to: pre_mention))
                blocks.append(.hashtag(hashtag))
                starting_from = p.pos
            } else {
                if !consume_until(p, match: { $0.isWhitespace }) {
                    break
                }
            }
        } else if c == "h" && (pr == nil || pr!.isWhitespace) {
            if let url = parse_url(p) {
                blocks.append(parse_textblock(str: p.str, from: starting_from, to: pre_mention))
                blocks.append(.url(url))
                starting_from = p.pos
            } else {
                if !consume_until(p, match: { $0.isWhitespace }) {
                    break
                }
            }
        } else {
            if !consume_until(p, match: { $0.isWhitespace }) {
                break
            }
        }
    }
    
    if p.str.count - starting_from > 0 {
        blocks.append(parse_textblock(str: p.str, from: starting_from, to: p.str.count))
    }
    
    return blocks
}

func parse_while(_ p: Parser, match: (Character) -> Bool) -> String? {
    var i: Int = 0
    let sub = substring(p.str, start: p.pos, end: p.str.count)
    let start = p.pos
    for c in sub {
        if match(c) {
            p.pos += 1
        } else {
            break
        }
        i += 1
    }
    
    let end = start + i
    if start == end {
        return nil
    }
    return String(substring(p.str, start: start, end: end))
}

func is_hashtag_char(_ c: Character) -> Bool {
    return c.isLetter || c.isNumber
}

func prev_char(_ p: Parser, n: Int) -> Character? {
    if p.pos - n < 0 {
        return nil
    }
    
    let ind = p.str.index(p.str.startIndex, offsetBy: p.pos - n)
    return p.str[ind]
}

func is_punctuation(_ c: Character) -> Bool {
    return c.isWhitespace || c.isPunctuation
}

func parse_url(_ p: Parser) -> URL? {
    let start = p.pos
    
    if !parse_str(p, "http") {
        return nil
    }
    
    if parse_char(p, "s") {
        if !parse_str(p, "://") {
            return nil
        }
    } else {
        if !parse_str(p, "://") {
            return nil
        }
    }
    
    if !consume_until(p, match: { c in c.isWhitespace }, end_ok: true) {
        p.pos = start
        return nil
    }
    
    let url_str = String(substring(p.str, start: start, end: p.pos))
    guard let url = URL(string: url_str) else {
        p.pos = start
        return nil
    }
    
    return url
}

func parse_hashtag(_ p: Parser) -> String? {
    let start = p.pos
    
    if !parse_char(p, "#") {
        return nil
    }
    
    if let prev = prev_char(p, n: 2) {
        // we don't allow adjacent hashtags
        if !is_punctuation(prev) {
            return nil
        }
    }
    
    guard let str = parse_while(p, match: is_hashtag_char) else {
        p.pos = start
        return nil
    }
    
    return str
}

func parse_mention(_ p: Parser, tags: [[String]]) -> Mention? {
    let start = p.pos
    
    if !parse_str(p, "#[") {
        return nil
    }
    
    guard let digit = parse_digit(p) else {
        p.pos = start
        return nil
    }
    
    var ind = digit
    
    if let d2 = parse_digit(p) {
        ind = digit * 10
        ind += d2
    }
    
    if !parse_char(p, "]") {
        return nil
    }
    
    var kind: MentionType = .pubkey
    if ind > tags.count - 1 {
        return nil
    }
    
    if tags[ind].count == 0 {
        return nil
    }
    
    switch tags[ind][0] {
    case "e": kind = .event
    case "p": kind = .pubkey
    default: return nil
    }
    
    guard let ref = tag_to_refid(tags[ind]) else {
        return nil
    }
    
    return Mention(index: ind, type: kind, ref: ref)
}

func find_tag_ref(type: String, id: String, tags: [[String]]) -> Int? {
    var i: Int = 0
    for tag in tags {
        if tag.count >= 2 {
            if tag[0] == type && tag[1] == id {
                return i
            }
        }
        i += 1
    }
    
    return nil
}

struct PostTags {
    let blocks: [Block]
    let tags: [[String]]
}

func parse_mention_type(_ c: String) -> MentionType? {
    if c == "e" {
        return .event
    } else if c == "p" {
        return .pubkey
    }
    
    return nil
}

/// Convert
func make_post_tags(post_blocks: [PostBlock], tags: [[String]]) -> PostTags {
    var new_tags = tags
    var blocks: [Block] = []
    
    for post_block in post_blocks {
        switch post_block {
        case .ref(let ref):
            guard let mention_type = parse_mention_type(ref.key) else {
                continue
            }
            if let ind = find_tag_ref(type: ref.key, id: ref.ref_id, tags: tags) {
                let mention = Mention(index: ind, type: mention_type, ref: ref)
                let block = Block.mention(mention)
                blocks.append(block)
            } else {
                let ind = new_tags.count
                new_tags.append(refid_to_tag(ref))
                let mention = Mention(index: ind, type: mention_type, ref: ref)
                let block = Block.mention(mention)
                blocks.append(block)
            }
        case .hashtag(let hashtag):
            new_tags.append(["t", hashtag.lowercased()])
            blocks.append(.hashtag(hashtag))
        case .text(let txt):
            blocks.append(Block.text(txt))
        }
    }
    
    return PostTags(blocks: blocks, tags: new_tags)
}

func post_to_event(post: NostrPost, privkey: String, pubkey: String) -> NostrEvent {
    let tags = post.references.map(refid_to_tag)
    let post_blocks = parse_post_blocks(content: post.content)
    let post_tags = make_post_tags(post_blocks: post_blocks, tags: tags)
    let content = render_blocks(blocks: post_tags.blocks)
    let new_ev = NostrEvent(content: content, pubkey: pubkey, kind: post.kind.rawValue, tags: post_tags.tags)
    new_ev.calculate_id()
    new_ev.sign(privkey: privkey)
    return new_ev
}