local config = require('pending.config')
local log = require('pending.log')

---@class pending.ForgeRef
---@field forge 'github'|'gitlab'|'codeberg'
---@field owner string
---@field repo string
---@field type 'issue'|'pull_request'|'merge_request'
---@field number integer
---@field url string

---@class pending.ForgeCache
---@field title? string
---@field state 'open'|'closed'|'merged'
---@field labels? string[]
---@field fetched_at string

---@class pending.forge
local M = {}

---@type table<string, string>
local FORGE_HOSTS = {
  ['github.com'] = 'github',
  ['gitlab.com'] = 'gitlab',
  ['codeberg.org'] = 'codeberg',
}

---@type table<string, string>
local FORGE_CLI = {
  github = 'gh',
  gitlab = 'glab',
  codeberg = 'tea',
}

---@type table<string, string>
local FORGE_AUTH_CMD = {
  github = 'gh auth login',
  gitlab = 'glab auth login',
  codeberg = 'tea login add',
}

---@type table<string, boolean>
local _warned_forges = {}

---@type table<string, string>
local SHORTHAND_PREFIX = {
  gh = 'github',
  gl = 'gitlab',
  cb = 'codeberg',
}

---@param token string
---@return pending.ForgeRef?
function M._parse_shorthand(token)
  local prefix, rest = token:match('^(%l%l):(.+)$')
  if not prefix then
    return nil
  end
  local forge = SHORTHAND_PREFIX[prefix]
  if not forge then
    return nil
  end
  local owner, repo, number = rest:match('^([%w%.%-_]+)/([%w%.%-_]+)#(%d+)$')
  if not owner then
    return nil
  end
  local num = tonumber(number) --[[@as integer]]
  local host = forge == 'github' and 'github.com'
    or forge == 'gitlab' and 'gitlab.com'
    or 'codeberg.org'
  local url = 'https://' .. host .. '/' .. owner .. '/' .. repo .. '/issues/' .. num
  return {
    forge = forge,
    owner = owner,
    repo = repo,
    type = 'issue',
    number = num,
    url = url,
  }
end

---@param url string
---@return pending.ForgeRef?
function M._parse_github_url(url)
  local host, owner, repo, kind, number =
    url:match('^https?://([^/]+)/([%w%.%-_]+)/([%w%.%-_]+)/(%a+)/(%d+)$')
  if not host then
    return nil
  end
  if kind ~= 'issues' and kind ~= 'pull' then
    return nil
  end
  local forge_name = FORGE_HOSTS[host]
  if not forge_name then
    local cfg = config.get().forge or {}
    local gh_cfg = cfg.github or {}
    for _, inst in ipairs(gh_cfg.instances or {}) do
      if host == inst then
        forge_name = 'github'
        break
      end
    end
  end
  if forge_name ~= 'github' then
    return nil
  end
  local num = tonumber(number) --[[@as integer]]
  local ref_type = kind == 'pull' and 'pull_request' or 'issue'
  return {
    forge = 'github',
    owner = owner,
    repo = repo,
    type = ref_type,
    number = num,
    url = url,
  }
end

---@param url string
---@return pending.ForgeRef?
function M._parse_gitlab_url(url)
  local host, path, kind, number = url:match('^https?://([^/]+)/(.+)/%-/([%w_]+)/(%d+)$')
  if not host then
    return nil
  end
  if kind ~= 'issues' and kind ~= 'merge_requests' then
    return nil
  end
  local forge_name = FORGE_HOSTS[host]
  if not forge_name then
    local cfg = config.get().forge or {}
    local gl_cfg = cfg.gitlab or {}
    for _, inst in ipairs(gl_cfg.instances or {}) do
      if host == inst then
        forge_name = 'gitlab'
        break
      end
    end
  end
  if forge_name ~= 'gitlab' then
    return nil
  end
  local owner, repo = path:match('^(.+)/([^/]+)$')
  if not owner then
    return nil
  end
  local num = tonumber(number) --[[@as integer]]
  local ref_type = kind == 'merge_requests' and 'merge_request' or 'issue'
  return {
    forge = 'gitlab',
    owner = owner,
    repo = repo,
    type = ref_type,
    number = num,
    url = url,
  }
end

---@param url string
---@return pending.ForgeRef?
function M._parse_codeberg_url(url)
  local host, owner, repo, kind, number =
    url:match('^https?://([^/]+)/([%w%.%-_]+)/([%w%.%-_]+)/(%a+)/(%d+)$')
  if not host then
    return nil
  end
  if kind ~= 'issues' and kind ~= 'pulls' then
    return nil
  end
  local forge_name = FORGE_HOSTS[host]
  if not forge_name then
    local cfg = config.get().forge or {}
    local cb_cfg = cfg.codeberg or {}
    for _, inst in ipairs(cb_cfg.instances or {}) do
      if host == inst then
        forge_name = 'codeberg'
        break
      end
    end
  end
  if forge_name ~= 'codeberg' then
    return nil
  end
  local num = tonumber(number) --[[@as integer]]
  local ref_type = kind == 'pulls' and 'pull_request' or 'issue'
  return {
    forge = 'codeberg',
    owner = owner,
    repo = repo,
    type = ref_type,
    number = num,
    url = url,
  }
end

---@param token string
---@return pending.ForgeRef?
function M.parse_ref(token)
  local short = M._parse_shorthand(token)
  if short then
    return short
  end
  if not token:match('^https?://') then
    return nil
  end
  return M._parse_github_url(token) or M._parse_gitlab_url(token) or M._parse_codeberg_url(token)
end

---@class pending.ForgeSpan
---@field ref pending.ForgeRef
---@field start_byte integer
---@field end_byte integer
---@field raw string

---@param text string
---@return pending.ForgeSpan[]
function M.find_refs(text)
  local results = {}
  local pos = 1
  while pos <= #text do
    local ws = text:find('%S', pos)
    if not ws then
      break
    end
    local token_end = text:find('%s', ws)
    local token = token_end and text:sub(ws, token_end - 1) or text:sub(ws)
    local ref = M.parse_ref(token)
    if ref then
      local eb = token_end and (token_end - 1) or #text
      table.insert(results, {
        ref = ref,
        start_byte = ws - 1,
        end_byte = eb,
        raw = token,
      })
    end
    pos = token_end and token_end or (#text + 1)
  end
  return results
end

---@param ref pending.ForgeRef
---@return string[]
function M._api_args(ref)
  if ref.forge == 'github' then
    return {
      'gh',
      'api',
      '/repos/' .. ref.owner .. '/' .. ref.repo .. '/issues/' .. ref.number,
    }
  elseif ref.forge == 'gitlab' then
    local encoded = (ref.owner .. '/' .. ref.repo):gsub('/', '%%2F')
    local endpoint = ref.type == 'merge_request' and 'merge_requests' or 'issues'
    return {
      'glab',
      'api',
      '/projects/' .. encoded .. '/' .. endpoint .. '/' .. ref.number,
    }
  else
    local endpoint = ref.type == 'pull_request' and 'pulls' or 'issues'
    return {
      'tea',
      'api',
      '/repos/' .. ref.owner .. '/' .. ref.repo .. '/' .. endpoint .. '/' .. ref.number,
    }
  end
end

---@param ref pending.ForgeRef
---@param cache? pending.ForgeCache
---@return string text
---@return string hl_group
function M.format_label(ref, cache)
  local cfg = config.get().forge or {}
  local forge_cfg = cfg[ref.forge] or {}
  local fmt = forge_cfg.issue_format or '%i %o/%r#%n'
  local icon = forge_cfg.icon or ''
  local text = fmt
    :gsub('%%i', icon)
    :gsub('%%o', ref.owner)
    :gsub('%%r', ref.repo)
    :gsub('%%n', tostring(ref.number))
  local hl = 'PendingForge'
  if cache then
    if cache.state == 'closed' or cache.state == 'merged' then
      hl = 'PendingForgeClosed'
    end
  end
  return text, hl
end

---@param ref pending.ForgeRef
---@param callback fun(cache: pending.ForgeCache?)
function M.fetch_metadata(ref, callback)
  local args = M._api_args(ref)

  vim.system(args, { text = true }, function(result)
    if result.code ~= 0 or not result.stdout or result.stdout == '' then
      vim.schedule(function()
        local forge_cfg = config.get().forge or {}
        if forge_cfg.warn_missing_cli ~= false and not _warned_forges[ref.forge] then
          _warned_forges[ref.forge] = true
          local cli = FORGE_CLI[ref.forge]
          local auth_cmd = FORGE_AUTH_CMD[ref.forge]
          log.warn(('%s not found or not authenticated — run `%s`'):format(cli, auth_cmd))
        end
        callback(nil)
      end)
      return
    end
    local ok, decoded = pcall(vim.json.decode, result.stdout)
    if not ok or not decoded then
      vim.schedule(function()
        callback(nil)
      end)
      return
    end
    local state = 'open'
    if ref.forge == 'github' then
      if decoded.pull_request and decoded.pull_request.merged_at then
        state = 'merged'
      elseif decoded.state == 'closed' then
        state = 'closed'
      end
    elseif ref.forge == 'gitlab' then
      if decoded.state == 'merged' then
        state = 'merged'
      elseif decoded.state == 'closed' then
        state = 'closed'
      end
    else
      if decoded.state == 'closed' then
        state = 'closed'
      end
    end
    local labels = {}
    if decoded.labels then
      for _, label in ipairs(decoded.labels) do
        if type(label) == 'string' then
          table.insert(labels, label)
        elseif type(label) == 'table' and label.name then
          table.insert(labels, label.name)
        end
      end
    end
    local cache = {
      title = decoded.title,
      state = state,
      labels = labels,
      fetched_at = os.date('!%Y-%m-%dT%H:%M:%SZ') --[[@as string]],
    }
    vim.schedule(function()
      callback(cache)
    end)
  end)
end

---@param s pending.Store
function M.refresh(s)
  local tasks = s:tasks()
  local pending_fetches = 0
  local any_changed = false
  local any_fetched = false
  for _, task in ipairs(tasks) do
    if task.status ~= 'deleted' and task._extra and task._extra._forge_ref then
      local ref = task._extra._forge_ref --[[@as pending.ForgeRef]]
      pending_fetches = pending_fetches + 1
      M.fetch_metadata(ref, function(cache)
        pending_fetches = pending_fetches - 1
        if cache then
          task._extra._forge_cache = cache
          any_fetched = true
          local forge_cfg = config.get().forge or {}
          if
            forge_cfg.auto_close
            and (cache.state == 'closed' or cache.state == 'merged')
            and (task.status == 'pending' or task.status == 'wip' or task.status == 'blocked')
          then
            task.status = 'done'
            task['end'] = os.date('!%Y-%m-%dT%H:%M:%SZ') --[[@as string]]
            task.modified = os.date('!%Y-%m-%dT%H:%M:%SZ') --[[@as string]]
            any_changed = true
          end
        else
          task._extra._forge_cache = {
            state = 'open',
            fetched_at = os.date('!%Y-%m-%dT%H:%M:%SZ') --[[@as string]],
          }
        end
        if pending_fetches == 0 then
          if any_changed then
            s:save()
          end
          local buffer = require('pending.buffer')
          if
            (any_changed or any_fetched)
            and buffer.bufnr()
            and vim.api.nvim_buf_is_valid(buffer.bufnr())
          then
            buffer.render()
          end
        end
      end)
    end
  end
  if pending_fetches == 0 then
    log.info('No linked tasks to refresh.')
  end
end

return M