137 lines
4.3 KiB
Crystal
137 lines
4.3 KiB
Crystal
class Ameba::Source
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# This class performs the heavy lifting in the source rewriting process.
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# It schedules code updates to be performed in the correct order.
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#
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# For simple cases, the resulting source will be obvious.
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#
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# Examples for more complex cases follow. Assume these examples are acting on
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# the source `puts(:hello, :world)`. The methods `#wrap`, `#remove`, etc.
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# receive a range as the first two arguments; for clarity, examples below use
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# English sentences and a string of raw code instead.
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#
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# ## Overlapping deletions:
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#
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# * remove `:hello, `
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# * remove `, :world`
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#
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# The overlapping ranges are merged and `:hello, :world` will be removed.
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#
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# ## Multiple actions at the same end points:
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#
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# Results will always be independent of the order they were given.
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# Exception: rewriting actions done on exactly the same range (covered next).
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#
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# Example:
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#
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# * replace `, ` by ` => `
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# * wrap `:hello, :world` with `{` and `}`
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# * replace `:world` with `:everybody`
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# * wrap `:world` with `[`, `]`
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#
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# The resulting string will be `puts({:hello => [:everybody]})`
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# and this result is independent of the order the instructions were given in.
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#
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# ## Multiple wraps on same range:
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#
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# * wrap `:hello` with `(` and `)`
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# * wrap `:hello` with `[` and `]`
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#
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# The wraps are combined in order given and results would be `puts([(:hello)], :world)`.
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#
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# ## Multiple replacements on same range:
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#
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# * replace `:hello` by `:hi`, then
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# * replace `:hello` by `:hey`
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#
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# The replacements are made in the order given, so the latter replacement
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# supersedes the former and `:hello` will be replaced by `:hey`.
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#
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# ## Swallowed insertions:
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#
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# * wrap `world` by `__`, `__`
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# * replace `:hello, :world` with `:hi`
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#
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# A containing replacement will swallow the contained rewriting actions
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# and `:hello, :world` will be replaced by `:hi`.
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#
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# ## Implementation
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#
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# The updates are organized in a tree, according to the ranges they act on
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# (where children are strictly contained by their parent).
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class Rewriter
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getter code : String
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def initialize(@code)
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@action_root = Rewriter::Action.new(0, code.size)
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end
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# Returns `true` if no (non trivial) update has been recorded
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def empty?
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@action_root.empty?
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end
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# Replaces the code of the given range with *content*.
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def replace(begin_pos, end_pos, content)
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combine begin_pos, end_pos,
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replacement: content.to_s
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end
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# Inserts the given strings before and after the given range.
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def wrap(begin_pos, end_pos, insert_before, insert_after)
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combine begin_pos, end_pos,
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insert_before: insert_before.to_s,
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insert_after: insert_after.to_s
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end
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# Shortcut for `replace(begin_pos, end_pos, "")`
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def remove(begin_pos, end_pos)
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replace(begin_pos, end_pos, "")
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end
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# Shortcut for `wrap(begin_pos, end_pos, content, nil)`
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def insert_before(begin_pos, end_pos, content)
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wrap(begin_pos, end_pos, content, nil)
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end
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# Shortcut for `wrap(begin_pos, end_pos, nil, content)`
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def insert_after(begin_pos, end_pos, content)
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wrap(begin_pos, end_pos, nil, content)
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end
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# Shortcut for `insert_before(pos, pos, content)`
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def insert_before(pos, content)
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insert_before(pos, pos, content)
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end
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# Shortcut for `insert_after(pos, pos, content)`
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def insert_after(pos, content)
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insert_after(pos, pos, content)
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end
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# Applies all scheduled changes and returns modified source as a new string.
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def process
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String.build do |io|
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last_end = 0
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@action_root.ordered_replacements.each do |begin_pos, end_pos, replacement|
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io << code[last_end...begin_pos] << replacement
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last_end = end_pos
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end
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io << code[last_end...code.size]
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end
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end
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protected def combine(begin_pos, end_pos, **attributes)
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check_range_validity(begin_pos, end_pos)
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action = Rewriter::Action.new(begin_pos, end_pos, **attributes)
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@action_root = @action_root.combine(action)
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end
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private def check_range_validity(begin_pos, end_pos)
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return unless begin_pos < 0 || end_pos > code.size
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raise IndexError.new(
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"The range #{begin_pos}...#{end_pos} is outside the bounds of the source"
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)
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end
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end
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end
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